## Don't Be a PV Efficiency Snob

This is a guest post by Tom Murphy, an associate professor of physics at the University of California, San Diego. This post originally appeared on Tom's blog Do the Math.

A common question I get when discussing solar photovoltaic (PV) power is: “What is the typical efficiency for panels now?” When I answer that mass-market polycrystalline panels are typically about 15–16%, I often see the questioner’s nose wrinkle, followed by dismissive mumbling that 15% is still too low, and maybe they’ll wait for higher numbers before personally pursuing solar. By the end of this post, you will understand why this response is annoying to me. At 15%, we’re in great shape: it’s plenty good for our needs. Let’s do the math and fight the snobbery.

A close-up of a polycrystalline photovoltaic (PV) cell, showing blue tint and a patchwork of crystal domains.

First, let’s look at the efficiencies of other familiar uses of energy to put PV into perspective. I will act as if I’m directly addressing the PV efficiency snob, because it’s fun—and I would never be this rude in person. This may not apply to you, the reader, so please take the truculent tone in stride.

### Snark Attack

So 15% is far too low for you? Perhaps you reason that laboratory prototypes and expensive spacecraft applications can get 40%-plus results, so let’s not take the plunge prematurely, given the abysmal 15%.

Perhaps you drive a car. Maybe you’ll stop when you realize that it converts thermal energy from burning gasoline into locomotive power at an efficiency around 15–25% (and this on a finite resource). We should wait for better.

Electric cars deliver battery-stored energy to the wheels at something like 85% efficiency. Now we’re talking. But the charging process imposes another 85% efficiency, and the real kicker is that the fossil fuel (or nuclear) plant supplying the electrical power is only 35% efficient for a net fossil-to-wheels efficiency around 25% (same ballpark as the gasoline car).

Hydrogen fuel cells offer no efficiency advantage in practice, achieving 20–40% for the round-trip hydrogen conversions, not including the efficiency of creating and delivering the electrical power to drive the formation of hydrogen.

If you’re low on energy, you might consider eating. But on second thought, our metabolic efficiency of converting chemical energy into mechanical output is similar to that of a car, so why bother? Turn up your nose.

Perhaps you are a fan of biofuels. This is perhaps the best apples-to-apples comparison to PV, being solar-driven. An Iowa corn field captures solar energy at a paltry efficiency of 1.5%! Okay, but we know by now that corn ethanol has a number of problems. Algae can be far more efficient, right? But even here, photosynthesis tops out at something like 5–6% efficiency under ideal conditions.

### PV is Actually Rather Remarkable

Considering this last point, I think it’s rather impressive that we beat biology by a factor of 3 in just a few decades of effort (biology had much longer to work on the problem). Moreover, 15% is perfectly adequate for our needs, as we’ll see at the end.

Qualitative assessments aside, it is rewarding to understand the origin of PV efficiency, and to appreciate that we’re not terribly far from the theoretical limit. The point is that we shouldn’t hold out for some arbitrary efficiency before we embrace solar PV: we don’t really need the extra efficiency, and in any case, physics has something to say about how high we might expect to go.

### PV Basics

A photovoltaic cell is most typically a slice of crystalline silicon 200—300 μm thick. (μm = micron = micro-meter = one-millionth of a meter). The construction can either be monocrystalline—slowly grown from a large single-crystal boule, or polycrystalline, cast in an ingot and with a patchwork of crystal domains in varying orientations (translation: pretty to look at). Monocrystalline varieties have a slight advantage in efficiency: like 18% vs. 15%. The cell is doped into what we call a p-n junction, which is basically a diode. What is important here is that the junction is very near the front surface of the cell, and it is here that energy is effectively harvested.

It works like this: a photon of light comes in from the sky, penetrating some depth into the silicon. If it has enough energy (imagine a sign out front: “you must be this tall to go on this ride”), it can pop an electron out of the lattice, leaving a “hole” behind.

### The Big Hit: Spectral Limit

This is all we need to know to take our first stab at an efficiency expectation. The first piece of knowledge is that photons below a certain energy cutoff called the bandgap energy (1.12 eV in silicon; corresponding to a wavelength of 1.1 μm) are not absorbed by the material: they sail right through as if going through clear glass. Second, the photons that are absorbed only need to have 1.12 eV of energy to liberate an electron out of the lattice. Any extra is wasted, popping the electron out at high speed. It rattles around the lattice, depositing its “sugar-high” as heat as it calms down.

Putting these together, we can say that if a perfect blackbody solar spectrum is incident on the PV cell (ignoring atmospheric effects on spectrum), we lose 23% of the light to infrared transparency beyond 1.1 μm, plus a thermal loss that increases with increasing photon energy (shorter wavelength). The net effect is that we get to keep 44% for PV energy production. This ignores many other real physical limitations that we’ll address below, but it at least represents an upper limit to efficiency expectations.

Considering only photon energy effects, a silicon PV cell ignores 23% of the incoming energy, and wastes 33% in light that arrives with more energy than can be utilized, leaving at most 44% available.

We see these effects in the figure above. At 1.1 μm, the photon is well-matched to the necessary energy for liberating an electron, and we use 100% of its energy. As we go to shorter wavelengths, a smaller fraction of the photon energy is utilized, resulting in 33% of the incident energy going to waste heat.

So this most basic analysis indicates that we are doing reasonably well to capture 16% efficiency out of a silicon PV cell when the crudely-determined upper limit is 44%. This is not much different from cars or power plants, in terms of how far below the theoretical thermodynamic limit we achieve in practice.

### Better than Silicon?

As an aside, the bandgap energy of silicon is 1.12 eV, corresponding to a wavelength of 1.1 μm. Other semiconductor materials have different bandgap energies. Why restrict ourselves to silicon—even though it is very abundant and we benefit from substantial knowledge and experience via the computer chip industry and related enterprises? I was curious to know what would happen to our 44% theoretical efficiency calculation if we allow ourselves to pick any bandgap.

If we decrease the bandgap wavelength, we squander more infrared light, but use the visible-light-dominated portion of the solar spectrum more efficiently. Longer wavelength bandgaps mean more photons are available, but achieving lower efficiency at visible wavelengths. Where is the balance?

Considering only spectral losses, silicon sits near the maximum possible efficiency, compared to other common PV materials.

I was amazed to see silicon perched near the maximum efficiency position in this trade-off. Who knew? A more careful treatment—using the spectrum as received on the ground and effects like those explored below—finds the peak performance closer to 0.9 μm (1.38 eV), at around 34%.

### Into the Weeds: Other Pernicious Limitations

A word of warning: we’re about to get into the nitty-gritty here, so if you’re already feeling a little queasy, there won’t be much harm in skipping to the last paragraph in this section.

Thus far, we have only considered the effects of the input spectrum for a single-bandgap device. But other physical limitations are at play, relating to where (or if) the photon is absorbed, the path history of the generated electron and hole, surface effects, etc. Here are four effects to consider (not a complete list):

1. The expected penetration depth of the photon into the silicon depends on wavelength/energy. Photons near the bandgap can travel a very long way before being absorbed, while high-energy photons are absorbed practically at the front surface.
2. PV cells are often fabricated with a reflective back surface (also acts as the electrode), so that photons passing through the entire wafer still have a chance to be absorbed on the rebound trip. The reflective barrier also reduces heating from infrared light that otherwise would be absorbed at the back of the cell.
3. The p-n junction is at a finite depth, so the photons absorbed above this are far more vulnerable to surface loss.
4. Shorter wavelength light suffers more reflection loss at the front surface than longer wavelengths, which is what often gives a blue tint to PV cells.

Absorption length (data from this site) is shown in the logarithmic plot below. This is only the characteristic depth of absorption, but the profile at any given wavelength follows an exponentially decaying probability of absorption, set by this scale.

Logarithmic plot of the absorption length in silicon as a function of wavelength.

At a wavelength of about 0.5 μm (green light), the absorption length is about 1 μm. Shortward of this, the third effect enumerated above becomes important. Longward of a wavelength of 1.0 μm, the absorption length becomes > 200 μm, and the light often reaches the back surface, where factor 2 comes into play.

After the absorbed photon creates an electron-hole pair, the electron wanders about, bumping this way and that, with no direction in life (diffusion). If it happens to run into the p-n junction near the front surface, it gets swept across toward the front, where it joins a flock of eager electrons itching to run out into an external circuit and do some work. If it wanders off the other way (deeper into the crystal) it may never find the junction; eventually re-combining with a “hole” elsewhere—often facilitated by crystal grain boundaries and surfaces, or by defects and impurities in the crystal.

Likewise, a hole generated above the junction may wander into the junction and be pushed to the back, in an arranged marriage (recombination) with an electron returning to the back side of the cell from service in the external circuit. The junction therefore acts like a pump, pushing electrons one way and holes the other—encouraging them to participate in a flow of current through an external device.

I made a simple model to account for these effects, where the probability of being “pumped” is unity at the junction, tapering linearly to some lesser probability at the front and back surfaces (pf and pb, respectively). Linear makes some sense, because—as I had to prove to myself via simulation—the chance of a random walk bumping into one extreme or the other is just linearly proportional to its starting position relative to these two boundaries. If the junction always sweeps the charge, cashing in its energy, while the surface has some fixed probability of gobbling up the charge and thus forfeiting the energy, the probability relation for points between is linear. This ignores internal recombination along the way, which dis-favors long-haul paths, making the back surface “hungrier.”

Model for evaluating conversion probability as a function of depth and penetration, ignoring bulk recombination losses. For a given wavelength, the absorption curve (red) is multiplied by the collection probability (blue) and integrated through the bulk. The front and rear surfaces have some probability of gobbling charge carriers that bump into them. The junction is actually much closer to the front, but is set back a bit for clarity.

Folding this effect together with the exponential absorption probability vs. depth, and allowing perfect reflection at the back, I can produce an expectation that accounts for the first three factors above. I don’t explicitly cover the front-surface reflection loss. Most new photovoltaics have an anti-reflection coating that reduces what would be a 30% surface reflection to just a few percent across most of the visible and near-IR band. But it gives out at the blue or near-ultraviolet end, allowing the reflection to creep back up to 30%. Since the PV response at the blue end is weak already due to surface losses and poor utilization of photon energy, I just absorb the extra reflection loss into the front-surface gobble probability, which is relevant primarily for short wavelengths because of their tiny penetration depths.

Okay—boy are we in the weeds here: let’s try to pull out. Putting these effects together, we get an expected efficiency of a silicon PV of 35%: not far off from other evaluations. Thus the real devices are in fact getting within about a factor of two of the theoretical maximum, which is better than we get in a lot of other, important domains.

Including absorption length and surface losses, the maximum possible efficiency drops to 35%, when front and rear surface probabilities are set to 0.5. Bulk recombination is not considered.

The modified curves appear above. I have added a curve for the probability of conversion. Now the photons close to the bandgap mostly sail through the device, even given a second pass due to the reflection at the rear. We get high probability between 0.6–0.9 μm because the light is converted to an electron far enough from the back face, but we are not yet suffering from the front-surface inefficiencies. The probability settles out at the 50% level for short wavelength, which I arbitrarily assigned as the gobble-factor of both the front and back surfaces. The 35% result can range from 28% to 41% as I change both front and back gobble factors all the way from 0% to 100%.

In summary, we have reduced our initial 44% expectation to something in the neighborhood of 35% by considering physical processes that are practically unavoidable. We could continue this trek, accounting for all the physical phenomena that lead to 16% efficiency in practice, but I think I have already overdone the point: that there are really good reasons why the efficiencies will not climb to arbitrarily high values. Basic physics stands in the way, and I am left impressed with what we’ve got.

### A Fantastic PV Tutorial

After developing the analysis above, I came across a great site explaining the fundamental physical processes involved in photovoltaics. The abundant interactive graphics are especially delightful. For the parts with which I am familiar, I find the information to be reliable and accurate. I was especially pleased to see confirmation of the collection probability scheme I implemented (you get the same linear effect in the interactive simulation if you neglect bulk recombination by increasing the diffusion length and crank up the surface recombination effect).

### PV Shenanigans

How is it that some lab tests or expensive spacecraft PV panels do better than the theoretical maximum calculated above? Most often, these are multi-junction devices. If we form a stack of PV junctions made from materials other than silicon, each with a different bandgap, we can more efficiently utilize the spectrum. We’d put a thin layer of material with a blue bandgap up front, followed by a green-bandgap material, and maybe silicon underneath. The longer wavelengths will sail through the first two layers and get used by the silicon. The short wavelengths, which had trouble in silicon, are more efficiently tapped by the layers in front. More of the photon energy goes into liberating the electron rather than into its velocity (heat), and more of the photons are captured.

Such devices are certainly possible to make. They are more complex, require less standard semiconductor materials, and can therefore be very expensive. For a satellite, the cost of the panels is a trivial fraction of the total cost, and launch mass means everything. So it’s worth paying a premium price to meet their power requirements in a smaller panel. For large-scale deployment, we’re likely to go cheap and low efficiency. In fact, it is more likely that a massive deployment would use thin film (amorphous silicon, e.g.) devices, which typically have efficiencies lower than 10% but are easier to mass-produce.

### It Comes Down to This

This brings us to some practical matters. Returning to the PV efficiency snob, efficiency effectively maps to area. A typical location within the U.S. gets an annual average of 5 full-sun-equivalent hours per day. This means that the 1000 W/m² solar flux reaching the ground when the sun is straight overhead is effectively available for 5 hours each day. Each square meter of panel is therefore exposed to 5 kWh of solar energy per day. At 15% efficiency, our square meter captures and delivers 0.75 kWh of energy to the house. A typical American home uses 30 kWh of electricity per day, so we’d need 40 square meters of panels. This works out to 430 square feet, or about one sixth the typical American house’s roof (the roof area of a two-car garage). What’s the problem?

If the calculation had yielded six times the roof area, or even one times the roof area, I would see the problem. There is even a problem with one-half, or one-third, since finding a suitable portion of roof facing the equator is an issue. But at 1/6, most houses can hack it (barring shade trees, in which case it’s not better efficiency you need!). Tripling efficiency to 45%, if even possible, would translate to 5% of your roof footprint. But there’s no magic in that. We’re already to the point where it’s feasible and practical from an energetics/area point of view. Stop crinkling that nose!

In fact, we can extend this argument to the nation or world as a whole. Even at 8% efficiency (typical thin film multi-junction device), we could generate all primary power with a minor land footprint, as the picture below shows. Efficiency is not the bottleneck. It’s usually price. And more complex, higher purity, higher efficiency cells don’t usually lower the price.

The land area needed to produce 18 terawatts (50% larger than 2010 value) using 8% efficient photovoltaics, shown as black dots. Source: WikiMedia.

We do not lack the area/resources on the planet to get enough energy from PV, even at half the current silicon efficiency. Other alternatives come nowhere close to being able to make this claim. As a side note, because North America uses 25% of the world’s energy at present, its dot may need to grow a bit, but not exorbitantly.

As reassuring as this picture is, the photovoltaic area represents more than all the paved area in the world. This troubles me. I’ve criss-crossed the country many times now, and believe me, there is a lot of pavement. The paved infrastructure reflects a tremendous investment that took decades to build. And we’re talking about asphalt and concrete here: not high-tech semiconductor. I truly have a hard time grasping the scale such a photovoltaic deployment would represent. And I’m not even addressing storage here. So while it’s physically possible, and the efficiency is sufficient to allow it, it remains a daunting challenge.

Could we even get started? Would we agree it’s the right path? Would it have much leverage against oil, given that it’s not a liquid fuel replacement? Will it always seem dreadfully expensive after being spoiled on ridiculously cheap fossil fuels? Once oil is in global terminal decline, economies will struggle to cope, and this may not seem the most opportune time to strike out on an unprecedented large-scale expenditure, whose costs and benefits will be debated hotly.

Have I ever mentioned that an easy solution is a voluntary reduction of energy demand? But this doesn’t sound like expansion/growth, so how would that idea ever gain traction?

Exciting as it might look, PV is not (yet) ready for the prime time. EROI are pathetic (<10) unless you are on a VERY good site. Claims for high EROI come from analysis that does not take account the balance of system.Indeed, EROI of the active component of the cell is rather good, but protection layer, support structure and inverter suck so much energy that the overall EROI is far from being exciting. My hope, it this would be a viable option within ten years however.

"Exciting as it might look, PV is not (yet) ready for the prime time.."

PV has been center stage of our family's electrical production/use for 15 years. Perhaps one of us is missing something. We certainly haven't missed the monthly bills, rate increases and more frequent outages, nor have we missed the foul, nasty contribution to planetary ecosystems we would have been making during this period. Some folks' comments here reveal just how limited human "thinking" can be. Now, off to utilize more of our "pathetic EROEI'...

How much subsidies did you get to buy it.

He's said this before. He got NO subsidies!

In consequence, he accepts to pay much more for is electricity. There is no magic here.

"He got NO subsidies!"

Actually, aug, that's not quite accurate. The moral subsidy we recieve is huge. While I understand that many folks, perhaps a vast majority these days, have little choice as to their energy sources, those who have options, especially those who are making a stand against renewables based on affordability, convenience and politics, who avail themselves of more than basic transportation, their annual expensive vacation, the latest I-Phone, etc., while assigning the true, ongoing, often irreversible costs to the future are guilty of permanently socializing their selfishness. I make no appologies for finding this morally repugnant.

Installation of PV farms has been halted in our county by the efforts of a wealthy few who consider these installations as an eyesore. It "spoils the view" from their obscene McMansions. I would take joy in dancing on their graves as they rot in hell. Their failure to use their good fortune to take a leadership position on these critical issues, especially considering their ability to self-educate and self-finance, is baffling, as they wrap themsevles in faux goodness. This position may seem radical until taken in the context of the radical changes and predicaments our children face. While our family struggles with finances every day, we don't struggle with our consciences, at least not on this issue. We're far too busy looking for ways to do more with less.

Thanks, I understand that completely.

This is one of the last EROI review (http://www.sciencedirect.com/science/article/pii/S1364032110003126). Unfortunately behind a paywall. It reflects the general consensus of the science today.

EROEI does not need to be as high for the homeowner, as the homeowner no longer needs to pay the inflated salary of electric company executives. Nor is it necessary to support as large a grid society-wide.
Grid parity, without subsidy, is here if you install yourself and budget carefully. I've started slowly collecting the components.
I'm not worried about storage cost - I can accomplish most of what I need when the sun shines, my trolling motor batteries will cover lighting after dark. Eventually I'll find a deal on a forklift battery. If I want it.

The fact that it is easy to purchase equipment that will give me power for what my power company charges me (\$0.17/kwr) on its face indicates EROEI is more than sufficient for my needs.

According to the conclusions of that article, EROEI is 12 for small residential PV in high irradiation areas, and still about 6 in low irradiation areas. So depending on where you live, it is above 10. Even with 6, it still gives a considerable net energy win, and given the often non existent alternatives, it does makes a lot of sense as one part of the renewables mix.

This is true only if the local electricity comes from non renewable sources. Calculations are done in primary energy. Thermal electricity give you a bonus of a factor 3. Put a third of the mix in renewable and the EROI is always below 10.

two questions:

How old are these studies? E-ROI studies for PV become out of date very, very quickly.

Is there an adjustment for energy's "market quality"? If all of the manufacturing process electricity comes from cheap surplus night time power, and the PV produces power during peak demand....that makes a big difference.

As wind power ramps up, there will be even more cheap night time surplus power....

As I said, this is the last review publish. I know that old PV studies are worthless.

Yes, but how old is the data? As best I can tell, most researchers stopped doing E-ROI/LCA analyses some years ago, as E-ROI appeared to be "good enough", and the question was no longer interesting.

"This is true only if the local electricity comes from non renewable sources. "
"Put a third of the mix in renewable and the EROI is always below 10. "

The EROEI of a given source does not change depending on whatever other sources are supplied next to it. You're simply gauging what you get out of it next to what was put into creating & implementing it.

The difference is primary energy. You need 3 units of primary energy to produce a unit of energy using thermal process. Hence, if your system overall produce its equivalent energy content in electricity, you get an EROI of 3 for free. Off course, this is more complex than that because you have to take account of the manufacturing process too. However, renewable electricity is a primary source. Hence, there is no such bonus.

That seems to be completely the wrong way round:

EROI = energy output/ energy input

Imagine the energy to make a solar panel was 300MJ of Coal, which was burnt to produce 100MJ of electricity. To get an EROI of 10, the panel needs to produce 3000MJ over its lifetime (assuming the energy in is defined as the primary energy in the coal, rather than electricity).

That means the panel produces 30 times as much electricity as was used to make it! So the panel is actually doing much better than indicated by the EROI figure. If you increase the denominator of the fraction, it makes the panel look worse than it really is. (I think actually the system boundary excludes the power plant, though, so this is moot)

Note also you are comparing industrial wind farm EROI with home-installed solar PV EROI, which is not a fair like-for-like comparison. Industrial scale PV likely has much better EROI.

Their has been something that I've been wondering for a while now. What exactly is counted as an energy input for EROI calculations? Does it include the energy cost of transporting materials? Does it include the energy cost of mining materials? Does it include some percentage of the embodied energy of all the different machines that are needed? What about a percentage of the embodied energy of the equipment used to transport the energy to it's final destination? If someone could give me some insight into how exactly this type of stuff is worked out it would be greatly appreciated.

EROI seems a slippery topic to me. Isn't it often easier to simply observe the cost effectiveness of an energy source? That doesn't necessarily mean we should only rely on current economics to make energy decisions. For example if you know oil is running out it makes sense to plan ahead and invest in a currently less economical but renewable alternative.

Another problem is determining true cost competitiveness given the multiple hidden subsidies when government constantly interferes in the free market. How much do we spend subsidizing oil by occupying Iraq for instance? And yes there are hidden environmental costs as well, but IMO these are dealt with most efficiently through environmental regulation.

I'm not that sure about EROI myself. I've only been familiar with the concept for a short time, but to me it seems like the EROI concept doesn't really tell me anything that is very useful[unless it's one or less]. It doesn't tell me how labor intensive it is to produce, install and maintain the energy source. It doesn't tell me how rare or common the materials used to make the energy source are, or how easy it would be to recycle those materials. It doesn't tell me how useful the sources energy outputs are to various end users. I think that cost tells you a lot more. It tells you something about the labor used, the materials used and the energy used, but I don't really think cost tells you everything about the usefulness of an energy source because money is like a veil that can both reveal and distorts what is behind it at the same time.

Mostly I'm interested in what societies are possible with the different technologies that are available to us. That question is very difficult to figure out with just EROI numbers. Actually that question is very difficult to figure out period which is why I think subsidies can be a good thing. We need to prepare for whatever might happen next. To that end I think a lot of subsidies are misdirected. Having a solar power house can be good, but having a solar powered solar panel factory would be better. Having EV cars can be nice, but having EV trucks to deliver food can be even better. I think that factories producing key goods, transportation for vital materials and farming are the key areas. Those are the things I think governments should be focusing on.

Because we live in a civilization that is mostly based on fossil fuels, the costs of different sources of energy are reflective of their utility in such an economy. Looking at costs tells you more about the current energy mix in a society than the relatively utility of those energy sources.

EROI is different. It says something (not everything, but something) about the inherent viability of an energy source regardless of what other sources are a available to a society. EROI can tell us a lot about "what societies are possible with the different technologies that are available to us", and that is especially interesting when we imagine that fossil fuels will not be available.

One part of the EROEI conversation that I try to incite every now and then is to look at the EROEI number of 'Homebuilt Solar Heating' Collectors, made from recycled scrap materials.

While the variable are surely far too diverse and vague to arrive at a conclusive and 'Hard' number, the result of looking for that number should be very illuminating.

I have a few collections of material that are gradually being turned into Hot Air and Hot Water Collectors, using Copper, PEX, Glass, Mirrors, Aluminum and Steel Framing (Folding Bedframes and Discarded Exercise Equipment are Excellent sources of high-quality materials!) and Lumber.

Particularly with the embedded energy in Alum. Copper, Glass and Steel, yet their relatively high availability in the waste streams, there is the potential for a very high level of return from such components, while the mfg costs of them, though real, were in large part accounted for within the product's intended use, and the RE-use of them is as much a bonus Energy Return to me, the maker, as it might be counted one of the Energy Costs.

While Pedro gave some very valuable insights into the misapplications and mishaps around Large-scale Solar PV systems, there was also a very familiar disdain shown for 'Bungalow' level solar.. and yet the heat and electricity that my family uses is no less real than the power represented by big utility providers.. it's just balancing Lots of Little Homes against a Few big Farms. Sure, there are lots of city dwellers, but there are still plenty of dwellings, single and multi-unit, all over the world that can take advantage of roof and yard space for individual sources, and these would certainly add up to considerable totals. China's Hot water collectors already demonstrate this well, both in cities and in the country.

Cost reflects a great many things, and all of those things are fairly current. As things change costs also change and things that were once expensive can become cheep while things that were once cheep can become expensive or impossible to find. In a future without fossil fuels costs will likely be very different, but I'm not sure if EROI will be exactly the same either. If the energy input of the EROI equation counts all energy inputs then a number of things might cause a technologies EROI to change. One such thing would be depletion of a vital material used in the technology. If people were forced to mine more energy intensive sources of that material it would increase the energy input and lower the EROI. Another thing to consider is transportation. Unless the technology is made on site with local materials it's use will likely involve transportation which can be considered an energy input. If the transportation used becomes more energy efficient that will raise the EROI, and if it becomes less efficient it will lower the EROI. We live in a very complex system and it is difficult to know how one part of our current system might function in a completely different system. That is why I like the idea of focusing on the vital areas first. If we can make vital things like transportation, manufacturing and farming more independent from fossil fuels we should have time to adapt to any unpredictable changes that might come about.

Transportation, manufacturing and farming will always out-bid personal transportation. We don't need to worry about them having enough fuel for quite a while. By the time oil production has fallen far enough to endanger them we'll have the time to transition to electrification.

OK, reading the payback time article properly (http://www.sciencedirect.com/science/article/pii/S1364032110003126), it is clear that they divide the power output of the PV by a factor of 0.35 to turn it into an 'equivalent' primary energy (the 'factor of three'). So my previous comment was in error (thermal efficiency is already accounted for).

It is pretty unclear how the payback time would change if you sourced the input energy from renewables, because you would need to know how much electrical versus thermal process energy is required. Most of the input energy (for silicon refining) appears to be electricity. Also, renewables like solar thermal and biomass might be a better source of thermal energy than resistance heating.

The difference is primary energy. You need 3 units of primary energy to produce a unit of energy using thermal process. Hence, if your system overall produce its equivalent energy content in electricity, you get an EROI of 3 for free.

Yvan, I agree with dashpool, you have it completely backwards and wrong.

To simply things, let's imagine a hypothetical solar technology that produces electricity, needs only electricity to be produced, and has an EROI of 3.

If you use a thermal technology to produce the solar product the first time around, and the thermal technology requires 3 units of thermal energy to produce 1 unit of electrical energy, then you get back from the product 3 units of electrical energy and your ERoEI is zero.

If you then use the product you produced the first time to produce more of the same product, you can produce 3 units of the product with the electricity you generated. These 3 units will deliver back 9 units of electricity, and your ERoEI is now 3.

Using renewables to create renewables delivers a better ERoEI if you are going to count primary energy in this way.

I'm not sure he has it backwards. A lot of manufacturing requires heat. Electricity can produce heat, but renewable sources are only just barely competing with fossil fuel for the production of electricity. So if fossil fuels are burnt directly to get heat they have an advantage(at least for now). Read this article for more.

You're right about heat, but Yvan still has the basic concept of EROI backwards.

One can look at some LCA studies for wind and solar and see that authors distinguish between the electricity and the thermal energy that go into production. To the extent that these renewables are dependent on heat energy for production, the advantage I talked about is less, and to the extent they only require electricity, it is more. But Yvan seems to think the advantage goes the other way, and he's just plain wrong about that.

Typical steam turbines have an EROI of 0.33, derived from the efficiency of 33%. The thing here is that all energy source are not equal at all. So when you compare EROIs try using the same type as input and the same type as output.

Current Energy Prices per Million BTU

Powder River Basin Coal – \$0.56
Northern Appalachia Coal – \$2.08
Natural gas – \$5.67
Ethanol subsidy – \$5.92
Petroleum – \$13.56
Propane – \$13.92
#2 Heating Oil – \$15.33
Jet fuel – \$16.01
Diesel – \$16.21
Gasoline – \$18.16
Wood pellets – \$18.57
Ethanol – \$24.74
Electricity – \$34.03

Even a process to make gasoline from coal with a crappy eroi of 0.05 is totally economic, since gasoline is worth 32 times more then some type of coal. On the other side, if you use wood to produce coal, even a great EROI of 30 is likely to be useless.

Back in time, we used only oil input and oil output in EROIs calculation. Therefore, you could easily check the usefulness of your method, since a EROI below 1 meant you used more barrels to extract less barrels, the process was obviously useless.

those who have options, especially those who are making a stand against renewables based on affordability, convenience and politics, who avail themselves of more than basic transportation, their annual expensive vacation, the latest I-Phone, etc., while assigning the true, ongoing, often irreversible costs to the future are guilty of permanently socializing their selfishness. I make no appologies for finding this morally repugnant.

Well said, but how does go about fundamentally changing human DNA and hard-coded selfish/wasteful behavioral patterns that are the result of millions of years of evolution which took place in a pre-technology pre-agriculture world not even remotely resembling the present? After a lifetime of observing my fellow homo sapiens, I have come to the conclusion that the reason most people are not changing their viewpoint is because they are *incapable* of doing so. The level of resistance to independent thinking and empirical, scientific data from most Americans is breathtaking, and I seriously doubt my countrymen are terribly unique in that regard. Those who are capable of breaking from the herd and thinking independently --even taking political positions diametrically opposed to the status quo or their religions, and those who are willing to sacrifice a little short term comforts for the benefit of faceless future generations number so few, well... that's why we have forums like TOD.

I seriously doubt that you or Ghung are significantly genetically different from those you find incapable of learning.

1) Learning new things takes a while, and

2) people are social animals - the whole society needs to gradually "get" something.

Its a combination of genetic DNA, but also of cultural DNA. Americans are brought up on the rugged individualist myth, and have incorporated it as an important part of their identifcation. Going against ones identify is tough. Other peoples with other values as part of their IDs, will probably less dysfunctional when faced with the need for sacrifices for the good of the group.

What personifies rugged individualism and independence more than generating your own power?

I suspect a differential between expected values and actual values here.

How much subsidies did you get for your nuclear/coal-derived electricity?

Here, the electricity is 97% renewable. Having to spend subsidies I would put it on wind turbine because the have much better EROI.

My question was directed at most electricity consumers, not just you--the costs borne by the public for environmental disasters not included in the rate base.

SI PV production is consuming a lot of electricity. this only displace the problem.

Where is electricity 97% renewable? I guess Norway or Iceland? The world is very very far from that.

Quebec, British Colombia, Manitoba. There is probably a few US states in the same situation. This is an important consideration as EROI is calculated in term of primary energy. This means that if most of your electricity comes from thermal process, your EROI is 3 times higher than the same technology installed in a place where the electricity comes from renewable energies. Even in country where the penetration of renewable electricity is sizable, EROI drops in proportion.

You've got it backwards. See above.

The Sanyo solar cell factory for one - the first cells produced are still being used to power the factory.

The costs for SI crystalline cells are falling fast and they are a bit better then the poly crystalline or thin-film type. The cost drop is the main reason that Solyndra failed.

Can't speak about Total EROEI - but can note on economics of Distributed Generation.
Image on Left - 500 watts PV per pole, Self contained twin Panel and Inverter, 2 wires with Ground, Each pole pumps out ~1A @ 250 VAC on cloudy days - 2x that on sunny days - Over 65 kWh per month average annual per pole. Total Hwd cost per pole at LAST years PV prices... under \$1800, quantity 1000, Including mount without permitting and Installation. Utilizing bew Dark Sky LED Light with 33% of consumption, billboard generates 35% surplus to the Grid. Designed to survive hurricanes.

Image on the Right - The most efficient small turbine available - 2.4 kW Grid Interactive Turbine - At least 5x the cost for a fraction of the monthly kWh. Lesson Learned: Good wind sites are NOT Common without a 100+ ft tower-Good Solar sites are as common as a roof. Note that this turbines efficiency approaches that of the big boys. Quite an amazing piece of hwd, but economics of PV deployment continuous to progress. Economics of the next generation micro-inverter should push in DG everwhere. Multiple "Top Secret" product rollouts at next weeks Solar Power International show in Dallas. Exciting stuff, PV is Sexy, has increasingly attractive ROI,& morphing into more appliance than power plant. Do Solar farms make as much sense? Ponder how the cash flows with the electrons with situation AS IS with \$\$ flying out of local economies.
Best Hopes for Distributed Solar and very local Power Generation.

Solar Power International show

Anyone going who could give a report of what is going to be coming out?

NAOM

www.solarpowerinternational.com/2011/public/enter.asp

Presentations / Dog & pony's shows available online. Much of it is training on product family's. I do a Summary so I can beg for \$\$ from my clients, Will post items of interest to TODers.

That link doesn't work, I got in through the .com oh, if you are not a member it is \$305 on the day - yike! Glad I am too far away to think about it.

NAOM

\$0.13/kWh * (12*65 kWh/a) / \$1800 = 5.6%/a

Yikes. So even in a very sunny part of the world, with expensive electricity, buying in quantity, and assuming zero maintenance and installation costs, solar power is still not quite worth it economically.

Close enough that it's worth doing anyway I suppose, but it's still a very long way from making any sense in more northerly latitudes.

If your interest is making a financial return on investment better than 5%, then maybe PV isn't the hottest ticket in town. If you read the Oil Drum, you probably don't have such a narrow view, understanding that we must find ways to cope with the ultimate fossil fuel decline in some way, even if the financial markets do not lead the way. I personally do not look to hedge fund managers to tell me how I should be building energy resiliency. A broader view is needed, and in this broader view, PV displays many perks.

Well said. It's way time to move beyond purely short-term finance driven decision making towards sustainability.

Agree with Styno, well said.

Another thing to add is that the stock market has not delivered as good a return as 5% over the recent past, and should probably be expected to do worse in the foreseeable future. Solarworld has had ads around here recently touting themselves as a better return on investment than financial products.

If you live in an area where 97% of electricity comes from hydro power, then indeed installing PV makes no sense currently, or probably even ever. So if your live in a region with 97% or renewable energy without power lines exporting electricity to regions with lower percentage and the government still decrees a high feed-in tariff for PV, then yes, you should probably throw your government out of office!

However, the vast majority of people live in areas in which reaching 97% of energy from hydro power is not technically possible.

So arguing that because there are some regions where PV doesn't make sense, PV in general is a bad idea is not really a helpful argument.

If you live in an area where 97% of electricity comes from hydro power, then indeed installing PV makes no sense currently, or probably even ever.

I was thinking about that this afternoon. Maybe hydro may not be as cheap and available in the future. As costs of fossil fuel power rise there may be pressure to sell more of the hydro electricity to FF areas to reap a better price and the locals may be forced to pay more. The job of the hydro corporations is to maximise profit to the shareholders after all.

NAOM

I was thinking about that this afternoon. Maybe hydro may not be as cheap and available in the future. As costs of fossil fuel power rise there may be pressure to sell more of the hydro electricity to FF areas to reap a better price and the locals may be forced to pay more. The job of the hydro corporations is to maximise profit to the shareholders after all.

The original reference was to three provinces in Canada. The big hydro companies in all three are provincial Crown corporations -- that is, government owned and presumably operated in the interests of the citizens of the respective provinces. While all three currently export electricity, I suspect they are all under obligations to meet provincial demand at reasonable cost first, and then to export surpluses. Certainly if I were a voter there, that would be my position -- cheap reliable electricity to support the local economy first, extra cash from outside sales second.

Some of the biggest hydro producers in the US are also government entities, although not nearly so neatly divided up. For example, the Western Area Power Administration operates transmission facilities and markets power generated by all of the Bureau of Reclamation, U.S. Army Corps of Engineers and the International Boundary and Water Commission.

While all three currently export electricity, I suspect they are all under obligations to meet provincial demand at reasonable cost first, and then to export surpluses. Certainly if I were a voter there, that would be my position -- cheap reliable electricity to support the local economy first, extra cash from outside sales second.

That's certainly true with respect to Hydro-Québec. The volume patrimonial or Heritage Pool sets aside a block of 165 TWh for domestic needs at a fixed wholesale price of \$0.0279. To give you a sense of how much electricity that represents, that's roughly equal to that generated in the states of Maine, Vermont, New Hampshire, Massachusetts, Rhode Island, New Jersey and the District of Columbia, combined, with Alaska thrown-in for good measure.

And, technically speaking, is this not a subsidy?

Cheers,
Paul

Absolutely.

Just like oil exporters, everyone including the local citizens would be better off with market pricing.

Sure, that would raise local power costs. On the other hand, the increased export revenues would more than make up for it in reduced local taxes, or however it would come back.

You imply the Quebec's Heritage Pool electricity is akin to a subsidy to Quebec ratepayers. But the statement is not backed up by facts. What is a subsidy?

A subsidy (also known as a subvention) is a form of financial assistance paid to a business or economic sector. Most subsidies are made by the government to producers or distributors in an industry to prevent the decline of that industry (e.g., as a result of continuous unprofitable operations) or an increase in the prices of its products or simply to encourage it to hire more labor (as in the case of a wage subsidy).

Definition of subsidy (according to Wikipedia)

So, is the Quebec government funding HQP? No. In fact, the average cost of a kWh (sum of generating, procurement and sales costs divided by the net sales volume) was 2.14¢ in 2010. Selling heritage pool electricity at 2.79¢ generates a nice chunk of change for the generation division -- \$1,075M net on a \$5G volume for a 21.5% rate of return. (details on page 10 of the latest annual report: http://www.hydroquebec.com/publications/en/annual_report/index.html ).

Section 52.2 of the Régie de l'énergie Act mandating a fixed price for heritage pool electricity ( http://www.regie-energie.qc.ca/regie/Loi/Loi_RegieEnergie_ENG.pdf ) was a way to introduce competition by putting a ceiling on HQP volumes so private actors could enter the generation market and a way to curtail the appetite of a low-cost generator with smallish variable costs in a monopolistic situation. You call that a subsidy?

yes, I can see California stealing N.W. government owned hydro power from their norther neighbors. Because they fail to build any significant power generation of their own. PV power "may" be good for homes but not for factories which need terawatts of reliable non interrupt-able power will not get their power from PV sources.

Need? Need? Demand is created and can be dealt with when necessary (I don't mean using exclusively monetary incentives).

California already has wind and PV contributing to their utility power. It can be tracked on a daily basis at:

http://www.caiso.com/Pages/TodaysOutlook.aspx

For today, peak so far (posting around 13:30p, west coast)
- 35,000 MW of total production
- 30 MW contribution by wind (egads, that is terrible, they are usually over 1,000 MW)
- 350 MW contribution by solar

Based on the power curve I doubt that the solar curve includes PV installations.
For comparison: The PV power curve in Germany can be seen here: http://www.sma.de/de/news-infos/pv-leistung-in-deutschland.html

Besides, PV together with the solar thermal power plants California should produce more than 350 MW of total solar power:
http://www.isuppli.com/photovoltaics/news/pages/california-to-continue-t...

Based on the power curve I doubt that the solar curve includes PV installations.

I believe you are basically correct. There may be some utility scale PV farms that are included in CISO's figure. However, there is no way they can have an accurate figure for net-metered commercial and residential installations, because not all of those are required to have an actual production meter on the solar. Without knowing otherwise, I'd guess that net-metered installations are simply not counted in their figure.

The actual peak of solar power production in California on a good day is probably somewhere over 1 GW, including what's counted at the CISO site. This page shows updated data from the Calfornia Solar initiative. Just under 1 GW in net-metered systems have been installed under the program, so add that to the CISO data and you have a rough idea.

none

By 'not ready for prime time', you might mean a variety of things. If you simply mean that EROI (Energy return on money invested) is not competitive with fossil fuels, then it is worth repeating that there is going to come a time when this is no longer true, and you need several decades to build the renewable infrastructure. If you factor in the environmental costs of burning fossil fuels, some estimates say renewables are already cost competative (http://www.hm-treasury.gov.uk/media/9/9/CLOSED_SHORT_executive_summary.pdf). My reading of our predicament says that 20 years ago would have been a good time to start installing massive renewable infrastructure.

If you mean EROEI (energy return on energy invested) then it is a matter of the current processes being optimized to minimize cost in an era of abundant fossil fuel. EROEI greater than 3 or 4 already produces a lot of excess energy, and EROEI will almost certainly go up as energy becomes more expensive. Here also the argument is all for starting earlier. If you can invest cheap fossil fuel energy in building renewable infrastructure, then you end up with much lower total system costs. I don't see any circumstances where tomorrow would be a better time to start building massive renewable systems than today. Maybe one could debate which alternative energy sources to invest in first, hoping that some would mature. And I could see an argument that we should invest in wind energy first, but solar is the only one that scales to global demand and I think we have to rapidly ramp up production starting now (or preferably a few decades ago). What metric would you use to determine when it is ready for prime time?

I as said, now EROI is too low. Low EROI means more pollution per kWh. Wind turbine have a much better EROI. Actually, the really best EROI comes from energy efficiency. This is why PV looks good in many situation. PV owner largely reduce their electricity consumption to make the PV affordable, which has the greatest impact on their electricity bill than PV itself.

Most available PV EROI studies explicitly include balance of system. See http://www.nrel.gov/docs/fy04osti/35489.pdf ,for example, which clearly includes protection layer and support structure and gives payback times with and without frame and balance of system that result in EROI over 10:1 for current systems including BOS, with significant increases coming in the near term.
Building integrated PV (like Dow's PowerHouse solar shingles , http://www.dowsolar.com, now available) will reduce EROI significantly by serving both power generation and roofing purposes.

I did not made my mind out of thin air. Last literature review I have seen on this topic EROI was always below 10. For BIPV, I did a literature review and EROI was always below 10.

The British Empire was built on an EROI much less than 10.

Solar is good enough now to serve.

2-3% efficiency of photosynthesis is good enough for the 3500 year old redwoods,but not good enuff for man. time horizons need to be longer.
Will we be using PV 1000 years from now or revert back to good ole photosynthesis.

Yvan Dutil, it is not possible to calculate the ERoEI of PV panels because their lifetimes are unknown. All the studies I have read refer to energy payback time which, five years ago, was 2 to 3 years including all energy inputs. Alsema did his studies correctly.

Here are a range of studies and advise about avoiding common mistakes when making life cycle assessments:
Energy Payback of Roof Mounted Photovoltaic Cells, Energy Bulletin, Colin Bankier and Steve Gale, June 16, 2006.

I know the work of Alsema. To my knowledge, everyone assumed a 25 years life time when calculating EROI. Alsema value are on the high side. Petdro Prieto will tell you that observed EROI is Spain is much lower than 10 because previous EROI studies dont atke account of the failure rate of solar cell, which is not negligible. Energy payback time of 2 years is normally observed in the very best locations. In addition, at the la Biophysical Economy meeting, I have been shown a presentation that claimed the PV has still to produce net energy.

Sorry, but what a crock. Failure rates from the field are reported to be in the <<1 % range after 10 years. Even considering a very long energy payback time of 10 years the panels still produce net energy. How about you substantiate your claims a bit more with sources instead of hearsay?

You should read the article you quote. The author is much more circumspect than you.

Perhaps you read that into his words, or maybe he is more circumspect then I read into his words. We can mince endlessly about words written or perceptually heard at some conference, but how about looking at the data?

The article reports hard numbers:

From 1994-2002, BP had ~2 million Solarex c-Si modules in the field. Over this period a 0.13% module failure rate was observed [6].

I also found another real-life endurance test report for 53 types of solar panels from 20 different producers produced in the `80s. From the conclusion:

Many manufacturers currently give a double power warranty for their products, typically 90% of the initial maximum power after 10 years and 80% of the original maximum power after 25 years. Applying the same criteria (taking into account modules electrical performance only and assuming 2.5% measurement uncertainty of a testing lab) only 17.6% of modules failed (35 modules out of 204 tested). Remarkably even if we consider the initial warranty period that is 10% of PMAX after 10 years, more than 65.7% of modules exposed for 20 years meet this criteria.

The definition of lifetime is a difficult task as there does not yet appear to be a fixed catastrophic failure point in module ageing but more of a gradual degradation. Therefore, if a system continues to produce energy which satisfies the user need it has not yet reached its end of life.

If we consider this level arbitrarily to be the 80% of initial power then all indications from the measurements and observations made in this paper are that the useful lifetime of solar modules is not limited to the commonly assumed 20 years.

Yvan, you are right in assuming that most LCA and EPBT studies assume 25 years (and even 30 years!) life cycle for panels. They are all academic with field tests in small plants controlled and installed in labs or in aging devices in the manufacturers plants or in the assessing companies. I know panels working well after 30 years...in the roof of the Solar Institutes in Spain, well cared and maintained. But there are no studies on massive deployments in real life.

But I know other solar PV systems abandoned 5 years after having been installed. Others remain idle for months, for lack of a poweer diode in the inverter. I have assessed and checked plants with the back panels corroded, after two years installed, because the sealing was not good enough to support salty fog, close to the sea. I have seen a multimegawatt plant completely flooded by a river level sharp rise. I have seen many real life things in Spain, which is the second installed base in the world, only after Germany. Real life is more complex than aging chambers. Hail storms (curious: I am in Sao Paulo now, where armoured private vheicles los the bullet proof guarantee in five years. I wonder if the tempered glass of the modules still will resist the impact tests of 5 cm hail at 20m/sec in year 15, for instance), dust, EVA and Tedlar insulations failing because they did not comply with the ultraviolet nominal resistance; bad solderings among cells, with hot spots, etc., etc. and not only from modules coming from China, but also from Germany, United States or produced in Spain.

Maintenance is also an essential part of life cycle. And maintenance, a totally fossil fuel underpinned activity has failed abruptly in many installations with the ongoing financial crisis, as many maintenance companies have simply gone broke and many suppliers committing to 5 years guarantees for modules or inverters, have simply entered into chapter 11 and are not able to maintain the plants, which degrade fast, if not maintained.

And yes, you are right. Our studies indicate solar PV EROEI’s for the whole of the solar PV installed plant in Spain for 2009 and 2010 much, much lower than 10. Of course, it is not only the fact that 25 years may not be true. We have given for good the 25 years life cycle mantra. But the problem is in the boundaries analyzed. What we call “extended boundaries” or SINE QUA NON activities for the solar PV plants to exist and produce electricity. The studies mentioned here, Alsema included, are considering only “restricted boundaries” for the Balance of System (BoS), but if we look to them under a more holistic perspective, we come to conclusions that leave the solar PV to very low, levels, unable to keep this 12 billion Toes/year society up and running as we know today.

It is worth remembering that solar PV installations in Spain, the sunniest country in Europe, yield twice more than the German solar PV installations, as per the official figures of both governments and in per MW installed. So, if in Spain the EROEI has resulted very poor, then in Germany must be horribly low. Exactly half of that of Spain.

And the most interesting thing is that as one of the conclusions of the study, IT DOES NOT REALLY MATTER very much how much we can progress in cost reduction or conversion efficiency at cell or module level, because when all the energy costs of the whole PV plant are integrated and the SINE QUA NON costs of these plants are included, the energy cost of the modules is a small portion of the total energy cost. Even assuming that the energy cost of producing, installing and maintain the cell is zero, the other SINE QUA NON societal costs keep the EROEI low, very low. By societal I mean ALL ENERGY COSTS that are attributable to the solar PV plants and that are requisites to put them in motion and maintain them producing in the Spanish society. Even worst, these costs are increasing dramatically in some cases, as the financial and global energy crisis deepens.

Keep tuned, because the book will be hopefully published by Springer and coauthored by Charles Hall, whose contributions, ideas, encouragement and direction have been and continue to be invaluable. There have been some peer reviews already passed and Charles Hall is making his last comments and summary.

I have seen many real life things in Spain, which is the second installed base in the world, only after Germany.

1. Well, if so many PV systems are defective, then there's no reason for you to religiously whine about FITs anymore. Renewable systems which do not produce any kWh, actually do in fact not receive a single penny from FIT...

2. Spain is hardly second after Germany considering the simple and obvious fact, that Italy is above 11 GW of installed PV-power: http://atlasole.gse.it/atlasole/

3. By the way, German PV-roof-owners not only receive less FIT-cents per kWh, but also less FIT-paid kWh per year (than sunnier southern countries). So, all these German roofs, you dislike so much, must create a loss for all their private owners according to your reasoning. But, luckily for the tax-payer: As opposed to the banks they won't need to be bailed out by the tax-payer. It's their loss - Yay!

1. Well, if so many PV systems are defective, then there's no reason for you to religiously whine about FITs anymore. Renewable systems which do not produce any kWh, actually do in fact not receive a single penny from FIT...

I would appreciate if you can quote any comment where I have “religiously whined” about FIT. A little bit less of arrogance and a little more of humility will no doubt benefit this thread. In fact, there is a big problem for many promoters that thought they will have economic returns of 15% and now they have to put money to pay back the credits. Go to the Spanish photovoltaic associations and ask the representatives. Producing less than expected IS NOT producing anything and therefore not receiving a single penny, is just receiving less than expected. In the first three or four years, not in the 25 of a supposed lifespan.

2. Spain is hardly second after Germany considering the simple and obvious fact, that Italy is above 11 GW of installed PV-power: http://atlasole.gse.it/atlasole/

I was referring in my post to years 2009 and 2010. It is clear that Spain was second to Germany. See any credible source, from BP statistic to ASIF webpage or EPIA

3. By the way, German PV-roof-owners not only receive less FIT-cents per kWh, but also less FIT-paid kWh per year (than sunnier southern countries). So, all these German roofs, you dislike so much, must create a loss for all their private owners according to your reasoning. But, luckily for the tax-payer: As opposed to the banks they won't need to be bailed out by the tax-payer. It's their loss - Yay!

Nonsense, apart from unnecesarily irritated argument.

First, the main and first bulk of the PV installed base was made with FIT higher than those of Spain.

Second, I do not dislike German roofs. I have only noted that a roof with modules considerably shadowed is a waste of time, an insult to the intelligence and a proof that many of the “green wave” in fact, have a surplus of resources that is not being used in a reasonable way. Or that they are caring more about their image than about common sense.

Third, I was talking about EROEI. This is an energy balance, not an economic balance. So, they may have a horribly low EROEI but if the FIT’s are high enough it may make an economic sense. Exactly the opposite you have stated.

I was referring in my post to years 2009 and 2010.

Then write so and do not write in the present form when referring to the past.

This is an energy balance, not an economic balance.

Besides that energy and economic balance are connected - particularly with PV-systems and wind-turbines: If PV was as costly and unreliable as you claim it to be it, it would simply not be economic and therefore not be built with those rapidly dropping FIT for PV.

I have only noted that a roof with modules considerably shadowed is a waste of time, an insult to the intelligence

By the way: Over 2 billion people in the world are still without connection to the grid and their highest probability to benefit from electricity is a small PV system and the reason why the costs of PV systems have dropped so rapidly is thanks to the FIT and the mass-production of PV systems that came with it:
http://www.usatoday.com/news/world/2011-07-02-india-rural-solar-power_n.htm
http://climatecrocks.com/2011/07/07/indias-poor-leapfrogging-the-grid/

Apologies for not having expressed in past tence (2009 and 2010) when referring to Spain as the second largest installed base in the world, after Germany. English it is not my mother tongue. In any case, even if it is third installed base, the case is that has a masssive, experienced installation, for being a country with 46 million inhabitants, versus the 80 of Germany, the 60 of Italy or the 310 million of the US. And producing double than Germany in per MW installed basis.

"First, the main and first bulk of the PV installed base was made with FIT higher than those of Spain."
Perhaps because the German EEG started much earlier when solar was much more expensive?

"have a surplus of resources that is not being used in a reasonable way"
Should they have bought a bigger car? Or go on an expensive holiday? Resources are often not being used in a reasonable (energy wise) way. Getting solarmodules to at least give something clean back is way better then a lot of the alternatives. But, of course you are entitled to your opinions.

"Or that they are caring more about their image than about common sense."
People spend lot's of their hardearned money to get a bigger car then they need, just for their image sake. Let them spend it on green tech that helps drive the price of solar power down instead of more wasteful other stuff.

"So, they may have a horribly low EROEI"
Well, you stated that often enough already, each and every time without anything to back that claim up (yes, I know you're going to publish a book sometime). And is the EROEI of tar sands much higher?

"but if the FIT’s are high enough it may make an economic sense."
Does 'grid parity' say anything? This is what PV already is in many places and quickly approaches in other places. Even if a FIT or subsidy is necessary this doesn't imply very low EROEI.

"First, the main and first bulk of the PV installed base was made with FIT higher than those of Spain."
Perhaps because the German EEG started much earlier when solar was much more expensive?

Of course, high PV system prices demand high FIT, if a country wants to take off. But this is only a part of the reality. Germans had foreseen a FIT descendant FITs, like Spain has made afterwards. Today Spain is giving some mere 14 cents of Euro/kWh for on the ground installations, less than Germany, although I am not following German FIT closely. The main reason is that the commitment of the governments with respect to the FIT is for 25 years and some of them need to grant yearly adjustments to the Consumer Price Index. This is giving the states a growing burden, as the PV base grows. There are many official and public claims of the Spanish government with respect to the problem that these ever growing and long lasting costs represent from them in this very moment. I cannot imagine what will have happened with those foreign investors installing in Greece with similar FIT and based in a 25 years deal, now that the Greek government cannot pay the salaries of the public officers for October 2011. The financial crisis is a crisis of a 87% fossil fueled society that has problems to continue growing.

"have a surplus of resources that is not being used in a reasonable way"
Should they have bought a bigger car? Or go on an expensive holiday? Resources are often not being used in a reasonable (energy wise) way. Getting solarmodules to at least give something clean back is way better then a lot of the alternatives. But, of course you are entitled to your opinions.
"Or that they are caring more about their image than about common sense."
People spend lot's of their hardearned money to get a bigger car then they need, just for their image sake. Let them spend it on green tech that helps drive the price of solar power down instead of more wasteful other stuff.

I understand your point and respect it, but I was not proposing a bigger car or an expensive holiday. I was just proposing to install in places where shadow is avoided. I do not think this is too much to ask is it?

"So, they may have a horribly low EROEI"
Well, you stated that often enough already, each and every time without anything to back that claim up (yes, I know you're going to publish a book sometime). And is the EROEI of tar sands much higher?

Again, I have not proposed to go for tar sands. If you want to know my opinion, I am much more in the Yvan line that energy conservation (the Negawatt) is the best option ahead. And I do not think that stating that the EROEI of solar PV ins Spain results very low (and much lower in Germany), has to be blamed beforehand.

What we have to do is to adopt the precaution principle, before investing like mad. I have heard much more many times the alibi that we need to invest in solar PV to drive the prices down to become “competitive”.

One of the things I have mentioned in this thread is that even the cells or modules go to zero, the total price of the system, when all the energy cost SINE QUA NON boundaries are considered, is reduced very little. And that many other ingredients of these energy costs are heading to energy and price cost increases, on the other hand. That is, that even the most sophisticated technology has asymptotes in price and energy reductions.

"but if the FIT’s are high enough it may make an economic sense."
Does 'grid parity' say anything? This is what PV already is in many places and quickly approaches in other places. Even if a FIT or subsidy is necessary this doesn't imply very low EROEI.

Go please and check where anybody has reached grid parity. See the countries with PV installations, as I did. 75% of the world installed base is in Europe and 15% in Japan and the US. All of them are still subsidizing the sola PV systems, after more than half a century of having discovered the photovoltaic effect. It may happen that the grid parity ends in a carrot-and-stick game on a kart, where the fossil fueled society is the kart and the carrot is the solar PV. When all the external boundaries are considered, it may happen that if fossil fuels and electricity generated with them increases, many of the ingredients of the solar PV full chain will go up consequently.

Two types of subsidies drive the world installations: those like in Germany, thought to sell patents, technology sophisticated testing, assembly and manufacturing and capture a market, rather than trying to sell modules, with Switzerland or the US also in this group and China emerging also. These groups, specially Germany, have done it quite well in getting a world leadership in selling technology and fixing the standards. To help in this, the government fixed the FIT, but in my opinion, more than to drive prices of modules down as a first objective, it was to get the technology edge in a BAU mode.

There is a second group and those trying to capture markets as solar PV sellers. China is targeting the world and is getting also results with its maquilas, without forgetting the technology edge, for which they are a little bit behind Europe or the US but probably not for much time. It is doubtful that the present prices are only the result of technology improvements and cost reductions, but probably also by an attempt to dump prices to cope markets. And to this effect, China has the means, the financial backup and the political will to cope the world markets.

If you add China and India to my percentages above, you will notice that out of FIT there is a solar PV wasteland, despite of some pretty photos of a 100 watt module being installed on the tinplated roof of a shanty house in Bombay. And curiously enough, these are countries with a lot of surplus of resources (of a fossil fueled society, never forget).

Finally, I will repeat: I have a solar PV plant in Spain and I have assessed some 30 MW of plants. I am consultant of solar PV plants, I like them. I have installed solar PV systems in remote or very remote locations throughout the world in telecommunication systems and they worked very well for many years (some of them, not 25 years, by the way).

I prefer to spend money in a solar PV plant than in a 4WD or in an expensive trip to the Seychelles. I do not like at all what they are doing with the tar sands. I do not like to escape forward of our society to a more intensive use of the remains of the fossil fuels in a postr peak period.

But on the other hand, I do not cheat myself, when the results observed until now indicate that, most likely, this is not going to replace the 12 billion Toes/year society with the mobility and functions as we know it today. Not in time and in volume.

And I know very well that these systems are hardly to become breeders of themselves and besides to be able to provide enough net energy to keep our high mobility and intensive society. And that they are NON RENEWABLE SYSTEMS, able to capture renewable energy flows for a life cycle, but then, they will need every X years a full replacement.

In central Europe FIT last only 20 years and FIT are paid for by the electricity consumers and not the tax-payers.

This is how it has to be and this is also why the countries which have this system in place make additional tax-income thanks to the renewable industry with its thousands of tax-paying jobs.

Unfortunately, the FIT also lowers wholesale electricity prices and the financial burden on the electricity consumers due to new renewable power plants is too low to give them a serious incentive to consume electricity more efficiently.
The average FIT burden per average German household is less than €0.18 per month!
http://www.solarserver.de/solar-magazin/nachrichten/aktuelles/2011/kw41/...

The FIT for large PV-systems is meanwhile below the average German household electricity price and continues to go down.

The average FIT burden per average German household is less than €0.18 per month!

3.53 €ct/kW-h * 3500 kW-h/year = €123.55 /year = €10.30 /month.

The renewable surcharge is going up to 3.592 €ct/kW-h next year, and heading towards 5–6 €ct/kWh.
http://www.germanenergyblog.de/?p=7526

Sorry, it actually says that renewable surcharge due to the additional renewable power plants installed in 2011 goes up by only €0.18 per month.
http://www.solarserver.de/solar-magazin/nachrichten/aktuelles/2011/kw41/...

The FIT is not heading to 5-6 €ct/kWh it is only increasing from 3.53 (2011) to 3.59 €ct/kWh (2012) despite all the additional renewable power plants installed this year.
Besides, even 5-6 €ct/kWh would still a small price considering the positive effects in the job-market and the additional tax income. And 5-6 €ct/kWh would unfortunately still be a too small of a financial burden to really drive efficiency measures.

Besides the FIT is not even being paid by the large electricity consuming industries and the rail operators. (They are just benefiting from the fact that FIT lowers wholesale electricity prices).

A list of possible failure modes and some observed anecdotal ones do not specify the frequency of those failures.

Written by Pedro Prieto:
Maintenance is also an essential part of life cycle. And maintenance, a totally fossil fuel underpinned activity has failed abruptly in many installations with the ongoing financial crisis, as many maintenance companies have simply gone broke and many suppliers committing to 5 years guarantees for modules or inverters, have simply entered into chapter 11 and are not able to maintain the plants, which degrade fast, if not maintained.

It sounds like you are referring to commercial scale PV installations. Do the Spanish maintenance companies that have been going bankrupt amount to 1%, 10%, 50% or 100% of the total in Spain? Why does one PV maintenance company going bankrupt prevent the owners of the installations from hiring another maintenance company to prevent fast degradation?

If there is a 50 MW PV array composed of 238,000, 210 W PV panels and a worker replaces 1 panel per week, the failure rate is .55% over 25 years. Frequent maintenance is necessary, but the failure rate is still small. Your characterization can be misleading.

Maintenance of a residential PV system is certainly not a "totally fossil fuel underpinned activity." Since embodied energy in tools was already expended, use it for best advantage. The power to run electric tools to maintain the system comes from the PV system. In the event of an inverter failure make sure you have got manual or battery powered tools and a backup inverter handy. A competent homeowner is also the maintenance person. Walking is the principle mode of transportation to access the system. Grow a garden to partially power the homeowner from principally sunlight. During my 20 years of owning a residential PV system, it has needed very little maintenance. If I suddenly disappeared, the odds are that it would continue running for years.

It sounds like you are referring to commercial scale PV installations. Do the Spanish maintenance companies that have been going bankrupt amount to 1%, 10%, 50% or 100% of the total in Spain? Why does one PV maintenance company going bankrupt prevent the owners of the installations from hiring another maintenance company to prevent fast degradation?

Yes, basically in Spain there are commercial scale PV installations, either on the ground (a big percentage) or on big surface roofs. More than half of the world is living now in urban cities and the idea of suburbia as known in Germany or US is a minority. Many of the big cities are vertically constructed now. When thinking in solar PV not only as a toy to power a bungalow or detached house in a developed country, but rather as the future energy source, then it is better to analyze big installations (by the way the best optimized installations).

If you want a figure, the Spanish main PV association indicated that in 2008, some 41,700 persons were working directly for the PV industry in Spain. In 2010 the figure was 11,000. Take the conclusions yourself. A company going bankrupt may handle the SW of the trackers and may cause a big problem if this SW fails, for instance, but there are many other related hurdles.

If there is a 50 MW PV array composed of 238,000, 210 W PV panels and a worker replaces 1 panel per week, the failure rate is .55% over 25 years. Frequent maintenance is necessary, but the failure rate is still small. Your characterization can be misleading.

The problem of the low EROEI is not only due to faulty modules or lack of maintenance, but also to the societal causes related to the plants. The failure rates you have given do not match with many of the data we have in Spain. And in a PV system, the failure may not be only in the module arrays, but also in the inverters, in the digital meters, in the trackers (if the plants are with trackers), in the SW, in the voltage sags and swells from the grid, in the stealing of modules or copper cable and in many other issues, generally not considered in the biased and interested LCA’s or EPBT’s.

Maintenance of a residential PV system is certainly not a "totally fossil fuel underpinned activity." Since embodied energy in tools was already expended, use it for best advantage. The power to run electric tools to maintain the system comes from the PV system. In the event of an inverter failure make sure you have got manual or battery powered tools and a backup inverter handy. A competent homeowner is also the maintenance person. Walking is the principle mode of transportation to access the system. Grow a garden to partially power the homeowner from principally sunlight. During my 20 years of owning a residential PV system, it has needed very little maintenance. If I suddenly disappeared, the odds are that it would continue running for years.

You are thinking in your personal situation. What we have observed is 4.5 GW of installed plants. The REAL LIFE is not always a good, conscious homeowner caring his/her plant and doing proper maintenance for its small system in the proper place. It is a promoter that is interested to show up and places a system on top of the German Bundestag (for instance) with modules looking in improper directions. The REAL LIFE is people locating plants in his own town, even it is covered by fog four months in a year. REAL LIFE includes people that goes with rolling PV flexible panels and is left abandoned by the provider the year after. It is people buying installations of a n-1 generation that goes phased out for lack of good soldering techniques. It is a buyer who was told that PV plants were giving a ROI of a 20% and bought with a lot of greed and very little care of the origin of the modules. It is a political decision to place a multimegawatt on top of an institutional building to sell themselves greenest than anybody else...but in Galicia, where it rains more than in Belgium. REAL LIFE is people installing in Northern Canada with the data of generation given in the Atacama desert. REAL LIFE is lack of maintenance in a school rooftop (20 kW) that is left idle many months because none of the teachers knew how to handle. And of course, REAL LIFE is a big multimegawatt plant being properly maintained and complying, for the time being, with the original budget, but noticing that the panels degraded 3% the first year, more than specified and the powerful investor forces the manufacturer to change the whole thing. To the investor, it does not matter, form the point of view of the expected income, as he gets substitute income from penalties and a new plant, but from the point of view of the EROEI it is a disaster.

One should be careful about the things included as failures in a life cycle assessment for ERoEI. The stealing of modules or copper cable does not reduce the overall ERoEI of PV panels because presumably they are used at other locations. They are a financial loss to the original owner.

A return of PV panels under warranty to the manufacturer is not necessarily a disastrous loss to ERoEI depending on the fate of the PV panels. The manufacturer may have resold them as used PV panels, recycled them or sent them to a land fill. A competent capitalist would have resold them.

Protracted down time due to teachers not knowing how to deal with a malfunction does not overwhelmingly degrade ERoEI. For example, assume 25 year life time of the system, 3 year energy payback time for the manufacture and installation, and 4 months down from the malfunction:

ERoEI without malfunction: 25 / 3 = 8.33
ERoEI with 4 month down time: (25 - .333) / 3 = 8.22.

There have been some malfunctions and down time with my PV system.
1. Two months after I moved in, I discovered that half of my SXP-44 array had disconnected due to heat dissipation from a wire connected to a junction box melting a solder contact. After discovering the fault, I repaired it and checked all of the wire contacts in the other junction boxes ensuring they made good low resistance contacts. The problem caused by incompetent installation has never reoccurred. I had a 50% reduction in power output for 2 months. Energy lost: ~48 kWh.

2. The SXP-44's were initially pointed 30 degrees west of south in azimuth and the riser for the wiring cast a shadow on the array until about 10 am. Due to a cloud pattern of clear in the morning and cloudy in the afternoon during the summertime, these issues caused about a 50% loss of power for 3 months out of the year and about 10% loss for the remainder. After 2 years, I corrected these problems by rotating the SXP-44's to an azimuth of 18 degrees east of south and placing the riser under the array. I also reduced the length of the wire between the PV panels and batteries reducing power dissipation in the wire by ~50%. Energy lost: ~187 kWh.

3. One of the wire splices I had made over heated and disconnected. I detected and corrected it within half a day losing about 1.1 kWh.

4. The roofing material on the shed upon which the PV panels are mounted needed to be replaced. Consequently the SXP-44's were disconnected for 4 days, but I made a temporary connection with a MSX-120 during that time. They were sunny days, so the energy lost was 8.6 kWh.

5. When I replaced the battery array, I disconnected the PV panels for a day during which I was mostly in town shopping and picking up the batteries. Energy lost: ~2.9 kWh.

6. Occasionally the fuse in the regulator for the SXP-44's has been damaged by heat (not blown from high current) or the relay has stuck in the open position. Energy lost: ~10 kWh.

I can not measure a power loss from bird dropping. Power loss from snow is included in the factor for cloudiness (75%). I can not think of anything else. Total energy lost from installation errors, malfunctions and maintenance: ~258 kWh over 20 years. This compares to the total energy, 15,800 kWh, that could have been generated, a minor 1.6% loss so far.

You and I have written at length about things that reduce the ERoEI, but I can also do the opposite based on my experience:

1. My SXP-44's are polycrystalline PV panels whose power output has not decreased over the last 20 years. To this day they still output 20 to 24 A depending on the season, just like they did in 1991.

2. My two year old KD-135 (mono- and polycrystalline) continues to output more power than its rating. I easily get 8.4 A (the rated short circuit current) at 14 V on hot days, even more on cold days.

3. I am located at ~2000 m elevation with no smog making the sunlight ~10% brighter and thus enhancing power output.

4. In the winter sunlight reflects off snow onto the PV panels increasing power output. This is especially helpful in recharging the batteries after a storm has caused cloudiness for several days.

5. Cooler than rated temperatures for 3/4 of the year increases the power output.

6. Sunlight reflects and refracts off clouds on partly cloudy days increasing the illumination. One time there was a circular opening in the clouds that acted like a lens focusing sunlight onto my array. The power output of my MSX-120 almost doubled, outputting 11.8 A for a while when it should have been outputting 6.4 A. I just happened to be measuring the current at the time. I wonder how many times this has happened on a partly cloudy day when I was not monitoring.

All these little things that enhance ERoEI neatly counterbalance the little things that diminish it.

I somewhat doubt that any commercial installation anywhere in the world is better optimized than my residential installation. I have high elevation in Arizona, clean air, few clouds, a latitude approximately equal to southern Spain, cool temperatures for 3/4 of the year, excellent air flow around the PV panels, PV panels pointing near the optimal direction, partial shading only early in the morning during winter, short wire length from PV array to load, maintenance performed within walking distance, simple durable inexpensive mounts and the embodied energy in my buildings, being used as part of the mount and an enclosure, not included as input energy because they previously existed and are used for other purposes. The ERoEI of commercial installations is probably lower than residential ones because the input energy is necessarily larger from constructing mounts, installing high voltage power lines, workers traveling to the site and enduring shading from adjacent rows.

Hi, BT. Your experiences are a bit like mine and tend to reflect the difference between those of us who are DIYers living with PV, and the grid-tied, turnkey "buy it and forget it" folks usually assumed these days. If there's a problem with the system (quite rare over time), we know almost immediately, find it and correct it. This has often led to even more optimisation of our system. I,ve come to a point where harvesting sunlight is much like growing a vegetable garden; things change seasonally and every year I look for ways to increase production or lower time spent on maintenance. Even though our PV panels are aging, our total production has increased over time. Building my own trackers was a eureka moment; total output increased dramatically, especially in winter, using mostly salvaged parts and a small investment in electronic components (about \$125 per array).

800 watts on an old satellite dish mount = single axis tilt and roll and a ~30% increase in annual production:

I've moved all of my arrays to these tracking mounts. Very easy to make seasonal adjustments, and a manual control allows me to rotate them for easier cleaning.

Our wasteful societies may need an EROI of 20 or 40. I wonder if the EROI for an individual living on a permaculture plot would need it to be so high. Perhaps 6 or 8 if more than enough. Once one gives up the latest high tech items and lives more simply that number may be very low.

Hunter gatherer work with an EROI of 10.

[Reference Needed]

ITYM "[Citation Needed]".

http://xkcd.com/285/

Those are fun.

I liked the one that ended with

"If you're quick with your knife, you'll find that the invisible hand is made of delicious, invisible meat."

I did indeed, and I always welcome an XKCD link.

TOD Commenting guidelines:

Commenters on The Oil Drum are considered guests and should behave accordingly. The staff reserves the right to delete comments and suspend accounts whenever we judge it in the best interests of our mission. Below are some guidelines that commenters are expected to follow:

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Besides that modern thinfilm PV reaches an EROI of around 30 and is increasing:

More importantly: What is the EROI of this best selling subsidized American car, who nobody really needs?

Exactly!

Yes, but the PV-system should be significantly cheaper than \$30k by now.

In Germany you can meanwhile get complete PV systems for €1.2 per W (granted not including installation):
http://www.gehrlicher.com/de/home/wholesale/special-action/
Or €33000 for a 27.6 kWp PV-system (before tax), which would produce over 10 times the energy an average European household requires (in US sun conditions).

So what are actual installed costs in Europe now?

So €1.5 per W is feasible.

Why is that 2 to 3 times lower than in the US? We are at \$4-7 per watt over here, according to the SEIA. Put another way, I'm not sure I believe your number.

I didn't come up with this number. This company does:
http://www.gehrlicher.com/de/home/wholesale/special-action/
And this offer is legally binding.
And according to the German PV-forum, installation costs are usually between €0.15 and €0.3 /W: http://www.photovoltaikforum.com/
So, €1.5 /W or \$2.1 /W is feasible for a 30 kW PV system as far as the low end of the price spectrum is concerned.
(Granted these are no top of the line PV-system components in the offer above. High-end inverters are costlier €0.2 to €0.3 per W: http://www.ebay.de/itm/SMA-STP-Sunny-Tripower-17000TL-NEU-OVP-Handlerwar... )

On the other hand PV-module-prices offered in the US (with 30 years warranty) have come down considerably as well: http://www.sunelec.com/ Besides, you can order them directly from China for less than \$1.1 /W: http://www.alibaba.com/product-gs/434755672/Poly_Crystalline_Silicon_Pho... (thinfilm modules even for less than a buck.)
So, I'm not sure whether I believe your \$4 - \$7 /Watt unless you are talking about a micro PV-system.
And even that should be considerably cheaper:
http://www.theoildrum.com/node/8461#comment-843215

As I said, the \$4-7 figure for the US comes from SEIA. See page 10 here: http://www.seia.org/galleries/pdf/SMI-YIR-2010-ES.pdf

Also, I work in the industry and this conforms with what I've seen.

I believe all your figures for the hardware, but...

And according to the German PV-forum, installation costs are usually between €0.15 and €0.3 /W: http://www.photovoltaikforum.com

This is the part I'm reluctant to believe. You didn't reference a specific post on the form, and with my rusty German I'm not going to go searching for it. The numbers you quote strike me as being low by about a factor of ten. They are roughly equal to the non-union wages I receive as an installer. (\$18 an hour, and I can install on average .5kW per 10 hour day.) I struggle to imagine how your figure can include not just labor, but also warehouse rental, management overhead, sales commissions, vehicles, permits, insurance, and so on. Especially in the residential sector.

There has been a fair amount of chatter in the industry press about how installation costs are now equal or greater than equipment costs, and how the heck are we going to bring them down. See for example this piece. They are talking about reducing installation costs by more than you seem to think installations costs ought to be. Are you sure you didn't move your decimal point?

Ok, I did some searching in the German PV-forum:

http://www.photovoltaikforum.com/angebote-f41/bitte-um-dringende-bewertu...
This guy got an offer for PV system installation costs of €150 /kWp:

Die Montagekosten der Unterkonstruktion sind pro KW mit 150€ veranschlagt

http://www.photovoltaikforum.com/allgemeine-anlagenplanung-f69/ist-der-m...
This Moderator says that the installation costs are between €150-300 /kWp if there is no need for a scaffold.

Im Forum wird von Montagekosten von 150-300€/kWp (ohne Gerüst und ohne weiteres Material) ausgegangen, je nach größe der Anlage.

http://www.photovoltaikforum.com/allgemeine-anlagenplanung-f69/montageko...
This professional "Solarteur" tells the guy who asks for advice about an offer from last year that €325 /kWp for installation costs are far too expensive even if scaffolding and AC-connection was included:

325 € / kWp Montagekosten finde ich absolut zu teuer für reine PV Installation. Selbst wenn die E-Installation AC-seitig und das Gerüst noch dabei wäre ist dies einfach zu teuer.

http://www.photovoltaikforum.com/angebote-f41/neuling-angebot-6-08-kwp-t...
This Moderator tells another guy who asks for advice about an other offer that installation costs of €216 /kWp are reasonable.

Die Montagekosten von 216€/kWp sind angemessen.

Right, okay, I see what you are doing.

In your previous post, you showed a wholesale price for panels around 1.1€/kW.

Now you are showing me contractors quotes that include a line for assembly costs around .2/kW, and you are adding that to the above number to get 1.3kW total installed cost.

Sounds fine, but it's not, because if you actually look at the full quoted price for the system, it's more. Take your first link to the forum above: the guy is actually paying "einen Preis pro KWP von ca. 2311,29€". That's \$3172 at today's exchange rate, which is roughly twice the figure you offered upthread, and getting closer to the \$4 per kW I mentioned.

What is happening is that the contractors are profiting off reselling the equipment, but instead of actually pocketing that profit, they are using it to pay for a large portion of installation expenses. What they call the assembly cost is not really the whole complete costs of installation, but rather a line item in the quote that they use to add money for special things they need to cover only for certain jobs, such as a scaffold, or a trench. We do something similar but not quite the same in the US industry: we have 'adders' that go on top of a regular quote for a system if there are special circumstances that will require additional expenses. But the normal expenses are built into the quote for the system.

Also, if the electrical interconnection is not included in some of these quotes, that's another part of the installed cost not being counted.

Now with all that said, there still seems to be a large discrepancy in installed costs of systems in Germany and the US, and that requires a lot more explanation. It's like another factor of 2. I'd really like to know what accounts for that, because as an installer, I know that we can't cut our costs by that much just by trying harder on the installation end.

They then tell him that he should get this system for way less than €2000 per kWp since it only has the 235 W PV-modules from Schott and not the best inverter.
Then the guy below says that he got a smaller 12.75 kWp PV-system with more expensive higher efficiency 250 W Schott PV-modules including everything for €2.06 /W.

ich habe gerade diese Woche eine Schott Anlage mit 12,75 kWP aufs Dach bekommen für 2060 Euro pro kWP. (incl. allem). Allerdings die 250 W Module.

Keep in mind: Schott are high quality German PV-modules. You definitely won't get them for €1.1 /W as opposed to the cheap no-name PV-modules from China.

But, here's an offer for a complete PV-system where they actually tell him to go ahead and order it:
It's also a higher quality PV-system with Sharp PV-modules and a Kaco inverter for €1.7 /W including installation and AC-connection.
http://www.photovoltaikforum.com/angebote-f41/-plz-49832-kwp-preis-1712-...

Es handelt sich um ein Komplettangebot für die Anlage, welches dann umgerechnet durch 13,5 KW rd. 1.712,- EUR/KW entspricht.
Fest stehen die Sharp Module und der Kaco Wechselrichter, welcher dann auf drei Teilbereiche der Anlage aufgeteilt wird.

If €1.7 /W has been done for a high quality 13.5 kWp PV-system then €1.5 /W must be feasible for a low end 30 kWp PV-system as I mentioned before.

I also wonder why PV-systems are apparently much more costly in the US than in Germany. Maybe resellers in Germany have a much lower profit-margin then their American counterparts or tile roofs one generally encounters in Germany are better suited for rapid and low cost installation of PV systems than the roofs you find in the US or the PV industry in the US is simply busy enough (and small enough) and is therefore not forced to adjust its prices.
But, I also remember reading on this same forum that installation approximately takes 4-7 hours per kWp (which also corresponds to the installation costs of €150 to €300 /kWp).

PS: In general, FIT are a much better instrument to drive competition in the renewable energy sector than subsidizing random technologies/concepts (e.g. Solyndra).

Well, that last one you linked to has some interesting comments, no?

"bei dem preis bleibt leider nichts für den solarteur über, entweder hat er nichts zu tun, oder,.....???!!!!"

At that price unfortunately nothing's left over for the installer, or else he doesn't have to actually do any work, or,.....???!!!!
(Do I have that about right?)

And then the next guy says to him, more or less, "You've been on vacation too long, in the last couple weeks crazy-good prices have been coming in." This is from about 2 months ago.

Basically I'm agreeing with the first guy here. Let's do the math...

But, I also remember reading on this same forum that installation approximately takes 4-7 hours per kWp (which also corresponds to the installation costs of €150 to €300 /kWp).

On my crews, installing a kW takes on average 6-7 hours with three guys. (Still going with the .5kW per man per day, which has proved strikingly stable over the long term and with different guys. I've kept a record.) Let's call it 18 man hours per kW. Well, divide €150 by 18 and you get €8.3. Are wages for skilled workers that bad in Germany? Do the installation costs include labor? Do they include labor and nothing else? Something just still doesn't add up in my book. I don't buy that German installers are twice as fast as Americans. Maybe somewhat faster, but not that much.

Maybe resellers in Germany have a much lower profit-margin then their American counterparts

I suppose I could believe that there is such a glut of panels in Germany that resellers are actually losing money, and that the real wholesale prices are even lower than the offer you linked to earlier. And that installers are taking advantage of this to quote crazy-low installation costs while making up for it with the lower panel prices.

or tile roofs one generally encounters in Germany are better suited for rapid and low cost installation of PV systems than the roofs you find in the US

Compared to asphalt composition shingle, concrete tile roofs add about %50 to installation times, so I don't think that's it.

or the PV industry in the US is simply busy enough (and small enough) and is therefore not forced to adjust its prices

hmmm... Basically you are saying there might not be enough competition in the US industry. That's possible. But it still think it hardly explains how the German industry can stay afloat at the prices you're showing me.

I really do want to know what the heck is going on here. Or over there, rather.

This competing 'Solarteur' said that the there's nothing left for the installer or the installer doesn't have any work. (Which I doubt since the general consensus on this forum is that they are very busy because at €2 /W the prospective owner of a PV-system can make profit margin of well over 5%.)

Of course these costs include labor. The initial salary of a roofer in Germany is €14.32 per hour (at 39 hours per week and including vacation) and their apprenticeship takes 2 years: http://de.wikipedia.org/wiki/Dachdecker#Gehalt.2FEinkommen.2FBrutto (Electricians make higher salaries but they don't do the majority of the labor.)

By the way, in countries like Germany, Austria and Switzerland many young people accomplish an apprenticeship instead of going to an university and the youth-jobless-rate is thus lower than in other countries. After a more elaborate apprenticeship (electrician or mult-skilled-mechanic) and passing an entry exam, people have still the option to go to an university of applied sciences and become a mechanical-engineer for example. I consider this a way better system for the job-market than getting every single person right through university, as for instance, the Obama-administration is proposing. (In 10 years from now the world will still need more roofers, electricians, carpenters, plumbers, locksmiths, masons etc. than social scientists).

Here's a video where you can see how Germans install a PV-system.
And here are some more:
(Search for Montage & Photovoltaikanlagen)
Maybe this gives one some more insight?

Maybe this gives one some more insight?

Not much. I see some racking systems that appear to be superior in convenience and speed of installation to what we are using, but I think this can only account for a small percentage savings in labor. Even if Germans somehow have a way of halving installation time (and thus labor costs) that doesn't account for the price differences.

Of course these costs include labor.

And do they include much of anything else that is additional to the equipment costs? We are still talking about differences in prices per watt between the US and Germany that are larger than the total labor budget ought to be in either country. So something is missing in the German prices, either because they have really found a way to cut the costs out, or because there are actually hidden costs somewhere, whether for the homeowner or ratepayers or taxpayers.

Perhaps German installers are not paying as much for overhead, insurance, sales commissions, etc? I would be interested to know how most German installers handle warehousing and delivery of materials to jobsites. Maybe the industry has a better system and/or benefits from bigger economies of scale. I can also believe that with Germany's FIT program, companies may not need to spend nearly as much money on marketing and salespeople, if the systems more or less sell themselves, which they don't over here. I know that closing rates on sales over here are pathetic, in the range of 15%.

Despite all we've talked about, I still find it to be a pretty inscrutable question. The differences are larger than any one particular thing could account for. It could be a little bit of a lot of things, which makes it no easier to figure out.

Why ya gotta be a hater?

I'm not hating. People can be free to drive whatever they want as long as their cars are not subsidized and fuel is taxed accordingly (and tax on work is lowered at the same time).

The people who are worrisome are those who disparage renewable options and efficiency measures, while there are thousands of serious problems in high need of being pointed out.

Yvan,

Substitute "EROI" for "efficiency" in the title and you'll see what I mean.

> My hope, it this would be a viable option within ten years however.

So because its EROI isn't as good as some other system, we shouldn't do it?
If oil has an EROI of, say, 16, and PV is has an EROI of 8, we should burn oil?

I see many good aspects of solar PV, even at relatively low efficiencies. It is extremely
simple, low-maintenance, and durable. If I had money to invest, that's where I would put it.

PT in PA

I'm not so sure we can be so picky about EROEI. The ratios we enjoyed in the 20th century were a once-in-history event; we're unlikely to find anything anytime soon that can challenge the now-dwindling ratio of fossil fuels at their best.

Having said that, it comes down to an issue of personal economics. If people perceive it as a good enough value to strap it on their homes and generate more of their own electricity, they will, and on an individual scale price-stability (as in you'll never pay much more than what you paid to install it over the 30 year life of the panels) is often more important than lowest possible immediate cost.

There are other considerations than EROEI on the scales of individual solar roofs.

However, the benefit of this, as in all renewables, is that the more we have installed, the more we have managed to stabilize the aggregate EROEI to whatever the ratio is of what we installed.

If EROEI is the fundamental yardstick by which the viability of our economies is to be judged, then surely there's something to be said for at least stabilizing the EROEI to a somewhat less prosperous, but sustainable, level?

EROI of ten is the lower limit to operate. This is the EROI of hunter gatherer society. As I made the remark to Charles Hall, it seams to be the EROI of any succesive tropic layer in an ecological system. EROI below 10 is not sustainable. If the average EROI drop below ten, you will destroy capital until the average EROI stabilized around ten.

EROI of ten is the lower limit to operate. This is the EROI of hunter gatherer society...it seams to be the EROI of any succesive tropic layer in an ecological system.

So we stick with BAU and the system as is fails from resource depletion.

Or we pursue renewables with lower EROEI and the system we know fails from capital destruction.

I see your point, but, all things considered, I don't think the individual can bother themselves with the fundamental unsustainability of the status quo. So long as solar makes economic sense on a microscopic level, and it does, then its going to keep expanding.

EROI of ten is the lower limit to operate. This is the EROI of hunter gatherer society.

You must be using a radically different definition of EROI than what I'm familiar with. As I see it, the EROI of a hunter gather society must be pretty dang close to zero because hardly any energy is returned that is not directly in the form of the bodily expenditure of energy. Are you saying that in hunter gatherer societies, one person's effort supports ten people's lives?

Folks might also like to be reminded of this, by Stuart Staniford.

The EROEI of hunter-gatherers has to be better than 1:1 or they starve to death. Energy out is the food energy they gather. Energy invested is the physical work involved in securing food. In fact, metabolic processes divert some of the energy away from investment in to the hunting/gathering. Full-time work would use something like 20% of the human energy budget for external work (the rest in baseline metabolism, as in sleeping, being idle). So EROEI of 5:1 is the approximate minimum for hanging on the edge of existence. 10:1 give hunter-gatherers time to sit back and enjoy life, which is usually what happens in such societies.

You're talking about individual hunter-gatherers, not a society. (Also you are talking as if baseline metabolism is a return, but it can also be considered in investment, especially the sleeping part.) In the sense that the individuals all eventually die, and that hunter-gatherer societies leave essentially no embedded energy behind in infrastructure, the EROI of the society as a whole is closer to zero. Actually I should say it's higher because of the use of fire, but you get the point, I hope.

I was considering saying in my last post that I'm not sure that talking about the EROEI of societies actually makes much sense. It makes a lot more sense to talk about the EROEI of a relatively discreet technology.

Let’s think about these hunter-gatherers and their energy requirements. Suppose that they engage in HG activities for an average of six hours per day. If they burn calories uniformly throughout the day their EROEI requirement is 4. If, as seems likely, they burn calories at above the average rate during HG activities then the EROEI requirement is lower than 4.

Now suppose either that environmental conditions change or that an HG group migrates to new territory where the energy input requirements for an hour’s worth of HG activity doubles. How much must the energy harvest increase in order to maintain their standard of living? Clearly they do not have to double their energy output and maintain constant EROEI in order to achieve this result. They merely need to increase their output enough to harvest the extra energy consumed during hunting. A pure energy balance analysis which neglects the labor intensity (or labor cost) of energy production is inadequate to analyze the economics of even this very simple case.

I think most potential users are much more concerned with the cost of electricity from PV vs the cost from the electric company.

I think you're right. But I also think there's a loud and sizable minority who are obsessed with efficiency numbers, and who sometimes distract people with their misinformation. Tom's post is addressed to those people, and those who might be misled by them.

I suppose there must be such a thing as energy produced per unit mass of investment capital. So an oil rig made up of a few steel trusses and extracting thousands of barrels of oil a day represents a small investment of material and massive returns of energy. Covering the planet with solar panels is a very large investment of material which will yield a relatively small amount of energy. Solar power has no future as a large scale solution.

"Solar power has no future as a large scale solution."

Yeah,,, seems some folks just haven't figured that out yet :-/

Solar photovoltaics is growing rapidly, albeit from a small base, to a total global capacity of 40,000 MW at the end of 2010. More than 100 countries use solar PV.[5] Installations may be ground-mounted (and sometimes integrated with farming and grazing)[6] or built into the roof or walls of a building (building-integrated photovoltaics)....

....Many solar photovoltaic power stations have been built, mainly in Europe.[43] As of December 2010, the largest photovoltaic (PV) power plants in the world are the Sarnia Photovoltaic Power Plant (Canada, 97 MW), Montalto di Castro Photovoltaic Power Station (Italy, 84.2 MW), Finsterwalde Solar Park (Germany, 80.7 MW), Rovigo Photovoltaic Power Plant (Italy, 70 MW), Olmedilla Photovoltaic Park (Spain, 60 MW), the Strasskirchen Solar Park (Germany, 54 MW), and the Lieberose Photovoltaic Park (Germany, 53 MW).[43] Larger power stations are under construction, some proposed will have a capacity of 150 MW or more.[1] A planned installation in China will produce 2000 megawatts at peak.[44]

http://en.wikipedia.org/wiki/Photovoltaics

Without subsidies none of these project can survived. That's the whole point.

THEN SUBSIDIZE, especially in the US, while we still have the option to do so. Wind, electrified rail, whatever, better get to it, keep it going. Of course, if folks don't think global warming and peak oil are their problem.....

Subsidizing solar is like subsidizing profligate waste. Imagine someone giving you a million dollars to flush down the toilet, and then rewarding you for it. As an alternative to oil, solar is a waste of human thought and effort. They ONLY way it could truly be profitable for large scale use is if a small amount of physical infrastructure is capable of capturing large quantities of energy at a high rate. This can only truly be accomplished in space, not on earth.

It's all about RATE of energy. We can have infinite solar energy, but infinite solar energy will come over a time-span of of millions of years. If man can get fusion to work, and that's a big IF, that will likely be a high-rate source of energy.

Given the rate at which resources are consumed to satisfy people's aspirations, man simply cannot continue to rely on ANY naturally occurring resources whatsoever. If man succeeds and lives for another 1000 years, one of two things is likely to have happened:
- Enormous breakthroughs in sub-atomic physics and the massive subsequent potential for practical use would have given man the power to fabricate one form of matter out of another.
- Alternatively, there would be a renewed bid for the conquest of space. Technology will have developed to transport humans from earth to other planets and moons, and perhaps raw material will be mined in these extraterrestrial regions. This would be a precarious extension of our current method of obtaining resources, which is drawdown. This is not to say that resources on other planets are as finite as on earth, but that perhaps very little is accessible.

One thing is for sure. In 1000 years, man will NOT be using solar panels, just as we no longer use ox-carts today.

All purely your opinion, unsupported I would add. My very successful experience with PV belies your opinions and exists in the real world now. Unlike some, I don't let (im)perfect dreams become the enemy of the good reality. Many folks (the ones who exibit some character) who have belittled my efforts over the years, have come to eat their words. The PV/renewable efficiency snobs still insist it isn't working, as if I have a secret connection to the grid somewhere. I waste little time on their biases and strawmen.

That's depends what do you mean by success.

Solar PV can be economic in off-grid regions, space, high radiance spots and others which I do not have mentionned. However, the main problem come from the grid connected people to run on solar powered electricity. It can be a moral success but not an economic success, with the prices that I've seen so far, taking into consideration storage and subsidies.

The thing is, it is hard to depict solar power as an economic success when it has such a hard time competing against coal, oil, gas and nuclear on traditionnal markets.

All that being said, that is not a reason to discard the technology, it is always possible to push the limits and change the rules going into the future and I hope your system help us to do so. Just don't sell it as worldwide-sized economic solution to the alternatives.

It's not that hard depicting PV's advantage over the others, as long as you are speaking with people who can understand the generally unaccounted costs and uncertainties of pollution and toxic wastes.

I'm on the grid. Success is asking those in denial what their electricity bill was for the year, and then telling them I made about 10 bucks selling PG&E electricity to sell to them.

It took four years for the system to pay for itself.

The grid subsidise your load management, it is acting as batteries. Furtheremore, the tarif at which you sold back the power is likely to be artificially bigger because of subsidies.

A typical closed system actually either waste power because of too much electricity available or lack power because of downtimes. So the closed system, the grid of US-west (US-east/US-center), is actually paying for managing your power.

This is derived from data of actual generation and cost of several solar PV plants. The "consumer actuals prices" are therefore likely to have been distorted (price bubble) by some way because you can't make energy out of vacuum (not yet as far as i know).

------------

Solarbuzz say module \$ per watt is \$2 to \$1, and is about 40% of final cost of a system, so the final price is between \$2.5 to \$5 per watt. Given a capacity factor roughtly the same as Germany (8%), we get 2.5 * 24 * 365 * 0.08 = 701 watthours or 0.7 kwh.

The ratio between capital cost versus production is between \$3.57 to \$7.14 for each kwh / year produced.

A typical coal plant produce 1000 MW, cost \$4 billion (I'm using high estimates here). We have 24 * 365 * 0.75 * 1000000 = 6 570 000 000 kwh / year and so the ratio is way better, at \$0.60 per kwh / year

A 2 cents surcharge on a 1000 MW 40 year plant for each kwh, using 10% interest rates is worth about : 6 570 000 000 kwh * 0.02 * ( 1 - 1.10^(-40) ) / 0.10 = \$1.32 billion

So the real cost is about 10% to 16.7% of solar power. Even if you have free solar modules, you aren't cost competitive with coal.

------------

Solar power is great, and I hope advancement will help its developement further, I love solar power and think it got great future. Best wishes on your installation. ;)

Hello alex555. I'm having a little trouble understanding your calculations. I have a few questions for you.

1) For he first calculation why is 2.5 included? It seems like that number should be 1 for one watt.
2) For the second calculation is .75 the capacity factor of coal plants?
3) Why do you allocate the cost of the hardware to just the first year of production? Shouldn't the cost be allocated to the hardware's total production over it's entire useful life?
4) Why don't you include the cost of coal?
Edit: Also now that I think about it, what about the cost of employees at the coal plant, and various other costs of doing business?

"In 1000 years, man will NOT be using solar panels, just as we no longer use ox-carts today."

?? First off, he might acknowledge you and I Ghung, and many others are using them today and they work well, and we as consumers have expressed our great satisfaction in them.. all that is left to undermine that success is to paint us as sadly deluded in our contentment.

Beyond that, of course, is that Ox Carts are certainly still used today, and if any of us was stranded with a broken vehicle, and an oxcart happened by, we might very well hop on and know it would still bear us along perfectly well, as it had a thousand years ago.

 . . . But I cannot imagine that the best that man can do is SOLAR and WIND. It's like going backwards in time.

Anyone is free to choose solar and oxcarts. Being satisfied with just this is like getting by on \$100 a month, living frugally and simply. But there are people in this world who have the instincts of the carnivore. They will NOT be satisfied until they have conquered the stars. They must have gigantic machines and resources at their command, and they must grow bigger, stronger, faster and more intelligent.

It is by riding on their backs that all of us take giant leaps in our evolution. They brought us machines, cars, airplanes, computers and the Internet. And it is they who will take us to the stars, and it will NOT be with solar and wind (or oxcarts).

Who said I'm satisfied with merely Solar (and Oxcarts)? (And PLEASE don't confuse my saying that we are Satisfied PV Customers with the idea that I think this is all that ever will be needed.. I'm going to presume your reading comprehension is more subtle than that)

'They will not be satisfied until they have conquered the Stars.. gigantic machines at their command.. '

Comic Books, SHOX. The people at this site are striving for a great deal more, and they are regularly both imagining and testing out the merits of various new ideas, but their feet are still on planet Earth as well. You might think that Solar and Wind are backwards now, but what built the machine you're writing on today? The Chair you're sitting in? What is powering it? Fuels a good bit MORE backwards than simply adapting the Sun and Wind. Fuels that are poisoning our air and water. Fuels that we are overreliant on and need to transition away from onto working backups ASAP.

If wind or solar is all that's available to run them in the near future, and no fantastic evolutionary leaps have popped out of the research labs yet, you will use them gratefully. I know you will.. just like you eat breakfast in the morning, even though it also is a completely primitive tradition. I just had some salami.. there's my Carnivore's Instinct.

I'm not at all against a good challenging argument, and look forward to the time when you can come up with one. Gratuitous arguments are a waste of time.

Bob

Besides the fact that collecting energy on your roof without any moving parts, without any cooling water, without any noise is very easy (as opposed to pushing an ox-cart) and reduces the load on the grid:
Most people just need a comfortable room, a warm shower, a hot coffee and as opposed to the extremely costly military: Never need to blow things up with high power densities. Also, people live spread out, so high power densities have very little relevance. In fact a roof can easily produce more energy than what the building underneath requires. The roof on this building in rainy Switzerland produces 448% more energy than the factory underneath consumes:

Meanwhile some PV thinfilm modules are cheaper per area than roof coverings which can reach up to €100 /m2 (a roof is always required anyway): http://www.baumarkt.de/nxs/8565///baumarkt/schablone1/Was-kostet-eine-ne...
PV thinfilm modules start at around €40 /m2: http://pvinsights.com/

Silicon is available in abundance and doesn't need to be burnt to produce electricity and one gram of silicon of a thinfilm PV-module on a US-roof can produce a hundred more electricity than one gram Uranium.

Carbon is at 0.03% and Uranium235 at 0.0000013%

(0.6 gram silicon for a 100 W thin-film panel: http://www.sciencedaily.com/releases/2011/05/110506165312.htm
At 1500 sunhours/year and 30 years lifetime, that's 7500 kWh/gram silicon.
For comparison: Current nuclear power plants only produce 38 kWh/gram uranium.)

Reducing the dependence on imported, limited resources with power producing roofs and local, tax-paying jobs would definitely make much more sense than spending 1000 times more on your inefficient military, which is apparently not even capable to get a hold of a bunch of barefooted religious nuts in Afghanistan...

PV thinfilm modules start at around €40 /m2

I don't see the m2 figure on the pvinsights site...

You get to this figure by combining the lowest thinfilm module costs on pvinsights with the efficiency of amorphous silicon thinfilm modules...

But how did you calculate the number of square meters?

1 m2 at 100% efficiency = 1000 W. (By definition: http://www.nrel.gov/docs/gen/fy04/36831l.pdf)
1 m2 at 7% efficiency = 70 W.
Thus, 70 W cost \$56/m2 = €40/m2.

(The cheapest amourphous silicon thinfilm modules on pvinsights have probably only an efficiency of 6% and would most probably cost even less than €40/m2).

Do you really not understand that our entire current civilization was subsidized by the stored energy of fossil fuel brought to us by accidents of nature millions of years ago?! And the enormous subsidies that continue to be drawn on future ecological debt? How is it possible to have such stunted and blinkered view of our current situation?

I don't have Nate Hagen's exact quote at hand but people like you have what he called "A longage of expectations". You and others like you must somehow be forced to come to terms with the reality that the era of cheap fossil fuels is over for good. Harping on the shortcomings of PV is totally missing the boat!

Without subsidies, the Army, Libraries and Public Schools also couldn't survive.

Collectively supporting an idea is not a proof of something being a mistake.. We just have to pick which of these is important, and determine How important.

Our entire road infrastructure has been subsidized to the max. It clearly is not feasible to have an interstate highway system. Actually, there is some truth to that but the point is that if we based our decisions on technology on whether or not it required subsidies we would abandon much of what we call civilization.

Pardon me, but what modern utility project hasn't been subsidized at some point? If I help my neighbor dig a well, did I subsidize it?

Estimated US PV additions for the 2011 calendar year 1.8GW, and growing rapidly. Subsidies are not as large as in most of the Eurpean cases.

The article decribed the current rather thich silicon cells. A large push is on to make silicon PV much thinner, which reduces the cost of the silicon -the largest cost component. So much thinner and cheaper panels will be available before too long. Likewise a lot of effort is going into BOS costs. That does create an argument however for waiting, if PV will be much cheaper in say two years, I would be strongly tempted to gorgoe two years output, for a better deal later on. One reason for subsidies, is to allow enough nearterm demand to drive the industry to that point.

There are some cases for higher efficiency. One is CPV (concentrated photovoltaics, where cheap area optics concentrates direct sunlight hundreds to a few thousand times. Then the cost of even fancy multi-junction cells becomes a minor part of overall system cost. Also systems which are limited in collection area favor higher efficiency PV. Most onvious would be transport applications, add a PV roof/hood to a plug in hybrid or electric vehicle, to extend sunny weather range, and achieve partial charging while parked. Here the available surface area in seriously insufficient to provide the full needs of the application, and higher efficiency helps a lot.

As panel costs drop as a percentage of total costs, the economic optimum point will move towards higher efficiency, since some BOS costs scale with collector area (mounting and wiring mainly). The best advice is to run the numbers for different efficiency/quality panels for your overall system, and pick the best juice per buck. Expect this tradeoff point to change as the technology advances.

Currently thin film can be had at roughly 14% efficiency (FirstSolar). It also has an advantage in hot climes, as the thermal coefficient (degradation of performance as the operating temp increases) is about half of silicon's. High efficiency silicon panels are now around 20%, with 22% projected. Don't expect much progress beyond that however. But for bulk projects economics probably favors low to medium efficiency panels.

The problem with concentrated PV is that you need a tracking system that eat your performance and overheating is a problem. Off course, there other optical design that can get around this issue but for reason we dont understand manufacturer dont want to deal with them.

Its true that CPV needs accurate 2-axis trackers, whereas tradiation PV doesn't. Its an open question whether CPV will be cost effective against panels -even in an area with high DSI (direct solar insolation, i.e. no clouds). Nevertheless several hundred megawatts of CPV are planned to be built during the next couple of years. It will be interesting to see if it can compete against cheap panels. In an area without too many clouds, the time profile of CPV will be better than for untracked panels, i.e. its output will be close to maximal except near sunrise and sunset, and that makes its power easier to integrate onto the grid. Also the area efficiency could be twice as high -because the PV component will be high efficiency multijunction circa 40% efficient.

We have a research project on that aspect of the problem. I will have an answer probably next year.

We have a research project on that aspect of the problem. I will have an answer probably next year.

I think that if you were going to do some kind of energy produced per unit of invested material calculation you would have to do it for individual types of material. For instance steel. Would you receive a larger energy return from investing a ton of steel in an offshore oil rig in the Gulf of Mexico, or would you receive a larger energy return investing that same steal in a wind turbine? That is the type of question such an approach might be good for. If the same approach was turned to PV a question that might be asked could be which individual PV technology gives the greatest energy return per unit of some specific material. If this was done for all materials used in PV it might be possible to figure out which blend of PV technologies would yield the greatest overall energy return given how much of those different materials is available. Ultimately if renewable are to be sustainable it might be a good idea to carry out such a project for all the materials used in renewable energy technologies taking into account the energy it takes to recycle all the materials used, but right now it might be a better idea to just focus on developing the technologies and installing as much capacity as possible because as fossil fuels run out the whole system dynamic will likely change in unpredictable ways.

I'm starting to get excited about PV. I took an installation class 10 years
ago, and the prices were \$600/100 watt module, and the avg installation price was
\$15/watt. Now just googling around the avg price is \$160/module, and even more
importantly a 5kw inverter is just \$2500. (10 years ago, a 2kw inverter was \$4k)

If this trend continues, in 10 years a 4kW system will be under \$5k.

The other side of the coin is electric bills. As you can see from the solar industry now, almost no one will spend \$20k to save \$80/month, but as we use more gas fired power plants and our nat gas gets exported as lng to china, eventually nat. gas will catch up to oil prices and
so will our electric bill. If one can spend \$5k to save \$300 or \$500 per month,
it will become a nobrainer.

I predict that within 5 years line-tie systems will be economically viable without subsidies.
eventually when the house construction business restarts (if ever) it will quickly become
normal to include a pv system for new construction.

My monthly electricity bill is 180 \$CAN and our house is heated with electricity (no heat pump, pure resistance) with a wood stove as secondary heating source. Since 97% of our electricity comes from renewable installing PV is a crime against humanity. In some place PV might be interesting, but with the actual technology it makes no sense financially and environmentally in most places.

In ten years from now, we will see. But wind turbine are already much better (EROI>20) and it will improve in the future. When you have a limited amount of resources to spend on energy production PV is not the best bet.

Yair...Good morning all. I believe it's pointless railing against blinkered attitudes expressed by posters such as Yvan Dutil.

He is clearly just here to stir and obviously has little concept of a world that exists beyond his tiny 97% renewable powered enclave.

He (apparently) is blessed with with an electricity supply so cheap that he can boast of still using resistance heating (pure resistance at that...what's the other kind?)

I live in a country where there is limited scope for hydro...from memory our longest river system has a fall of around one hundred meters in two thousand kilometers. We have a limited amount of recources to spend on energy production...there is not much wind in the outback.

What the hell other than PV would Yvan Dutil consider to be our 'best bet'? Incidently our electricity from the grid is around twenty three cents per unit.

Cheers.

Yvan - your comments are enjoyable to read for me - you bring up some good points - I think it is good to stir the pot occassionally from a different perspective.

I think for utilities you are right, wind makes more sense. I am not a fan of PV farms. I beleive you are correct in that there is a good argument that this is a waste of resources.
Wind for the home owner, on the other hand, is a waste of resources in almost every circumstance. I usually doesn't work out economically, the good wind is normally not where the homes are.
PV on the other hand works for the homeowner economically. There is a good argument that it will work out for the home owner resource wise also. Yes, a large area, a lot of resources, but roofs have the area, and roofing materials and housing already consume vast resources.
May the resources purchased by the future homeowner work for him/her twice.
Your perspective is that of someone who lives in a large city and rents. It is not wrong, but is different from a rural person who owns his own land and home.
Your EROI studies aren't the last word. They are important, but are only as good as their assumptions.

Last I looked at install stats, commercial roofs are more important by a large factor than home roof installed PV (total megawatts installedwise), and PV farms are more important still. If the country is going to acquire significant solar assets, those less glamorous sectors are key. Also the LCOE (levelized cost of power), is better for larger installations, due to economies of scale issues -and also for PV farms more optimal locations wrt. insolation. A mix of locations means lower output variance for the grid as well.

Commercial roofs make a lot of sense. Homes make a lot of sense. PV farms still, to me have the feel of resource waste. To me the most optimal location is at or near the point of use - I think transmission loss, additional infrastructure cost, environmental cost, etc outweigh advantages re insolation (do you mean farms in the desert southwest?).
All the PV farm projects I read about are expensive & small - 50 or 100 MW - and they use a lot of material and area compared to other grid power sources. I think ultimately not much will come of them.
It seems point of use is the real advantage of PV, whether it be a home, business, or manufacturer. Note the solar panels that have appeared at US border crossings, even though they are on grid. Or the panels at many US military bases now.
There is no danger that PV development will slow down soon - do you really think we need grid solar farms? A few could do little harm as a technological test bed of sorts, but a lot of them? A huge investment for what you get - the technology is moving ahead for point of use installations anyway.
My mantra, I think, ought to be no middlemen for my energy. My batteries maybe.

My mantra, I think, ought to be no middlemen for my energy. My batteries maybe.

I'm not worried about energy for my domicile (its already 3/4 solar), but energy for maintainence of some sort of industrial society/economy. PV on the roof will not be able to power an aluminum smelter! For important industrial processes with large energy inputs, power will still have to be produced elsewhere and pumped in. PV farms, can be one source. We will need renewables for industrial/ agricultural, retail, government, health facilities etc. as well as houses and transport. This will require all sorts of plants, not just rooftops and parking lot covers.

And again, since most renewables come from unsteady flows, the more diversified the geographic sources the less variable it will be.

PV on the roof certainly won't power an aluminum smelter . They are always located near a source of cheap, reliable electric baseload power. EG Hydro Quebec with its Manicougan reservoir etc and the smelter at Chicoutimi on Lac Ste Jean.
Think of how much material would be required to power an aluminum smelter with a PV farm. In an increasingly FF constrained world, I think energy intensive industries will find the best option is simply to be located near large hydroelectric resources. Areas that do not have such a resource will find it difficult or impossible to compete (excepting of course any area that is able to successfully utilize eg failsafe modular nuclear reactor technology).

A few numbers, expected PV installations in the US this year 1.8GW. How much of that is residential rooftops? About a quarter of a GW. At this point residential rooftops hardly matter, the big growth area is utility sized farms.

One could debate that rooftop PV matters perhaps even more, as they tend to have an impact on the lifestyle of the owner as well. ;-)

For me, the decision point to deploy solar pv was the moment I looked at my suburban lot and asked myself - what was the lot producing? A few years back, partially through this site, I realized that most suburban lot aesthetics revolved around the dubious status that comes from conspicuous consumption (non-productive lawn, non-productive trees and shrubs, non-productive landscaping, excessive exterior lighting). With that realization came a decision to move towards more productive ownership: gardens, fruit trees, rainwater harvesting, and solar panel energy production. A decision reinforced by learning how my German relatives lived. A slow journey for sure, but I feel like I'm moving in the right direction. Consumption -v- Production. Dependence -v- Independence.

The Germans installed more PV in 2010 than the Americans have in 60 years.

Ok, we could say, "Well, that's the Germans." But the friggin Italians did
the same thing last, which seems even more inexcusable. (And it's not like
German has a solar climate, really.)

This is a technology that was invented at Bell Labs, and we are just pissing our

The German feed-in tariffs cost them about \$15B a year, one tenth what Americans are spending on our wars. On the positive side, steep declines in module prices driven by
rapid expansion of production in China and elsewhere steadily improve the economics.

Having lived with solar power for nearly 15 years now, one thing that has surprised me is how maintenance free and reliable my system has been. My "maintenance" costs in that period: zero. Things that have gone wrong: zero. Headaches, also zero. This in contrast to, say, solar hot water which does require some routine upkeep and attention.

Yes, solar is still tiny, a small rodent among the gigantic fossil fuels, but there are intriguing inklings afoot.

Subsidies are so expensive that German are cutting them now, which as largely reduce the sell of solar panels. Also, they start to have problem of grid stability, solar energy having even less stability than wind.

You can rather see it as they are cutting the subsidies, because the price of PV has come down much more rapidly than expected. Despite all of the extra cuts in subsidies (to keep up with the rapid reduction in prices), installation capacity has continued to go up and far exceed the expected amount. The plan was to install about 3.5GW per year, however last year it was more like 7GW, despite the extra cuts of subsidies. This year, again the installations will exceed the 3.5 GW intended with expected somewhere between 4 - 5 GW, resulting in yet more extra cuts.

Despite all these cuts, profitability has remained very good for PV systems (due to the rapid cost reductions), resulting in these large capacity buildups. This is despite the fact that Germany has one of the lowest feed in tariffs in the world for PV and is not a very sunny place. In 2012, PV prices will be more or less at grid parity for small systems.

So far most households are also still willing to pay the extra cost of electricity of currently 3.5 ct/kwh to finance the feed in tariffs and it remains popular despite the effort of industry to discredit it as too expensive. In general Germans do recognize that something has to be done and that it won't be cheap, but there is not much of an alternative.

"Subsidies [for PV] are so expensive"
This is nonsense.
- All electricity users (except the heaviest ones) in Germany pay about 1.5 €ct/kWh extra to finance the build-up of solar renewable energy industry. The users barely notice it. Others argue that renewable energy is already reducing the price of electricity, which essentially means that the EEG costs are providing net profits for the users.
- Subsidies are a given for our power supply as there is no free market. Every form of electricity production benefits from subsidies. Coal for instance receives 13.8 billion € annually for just keeping the mines open and a lot more for not having to pay for externalities (air polution, health problems, climate change, etc.)

"that German are cutting them now"
I assume you assume they did this because it was becoming too expensive? This is nonsense for two reasons:
- The whole German EEG was designed from the ground up to annually cutting the subsidies to force the industry to work more efficiently year by year. Once the subsidies reach 0, industry must do without.
- Apparently the PV industry is doing such a good job improving efficiency that they themselves asked to have the subsidy reduced.

"which as largely reduce the sell of solar panels."
Indeed, new installations in 2011 won't likely reach the previous record levels of 2010. One of the limiting factors is the new rule that forbids (under EEG rules) construction of PV plants on marginal fields in eastern Germany, another is that continued exponential growth is physically impossible. However, combined installation will still see the second biggest increase, a very substantial multiple GWp. Still, a nuclear reactor worth of new PV per year is impressive. Also, at the same time the subsidy was reduced the price of solar panels dropped 30-40%, so the payback time for a new PV installation is not much different then in 2010, again pointing to other factors for not reaching a new record.

"Also, they start to have problem of grid stability, solar energy having even less stability than wind."
New highways are being constructed to improve traffic stability all the time, I guess that's an argument against the sale of vehicles? Yes, Bavaria has to improve it's links to the rest of Germany, Switzerland and Austria. Probably have to do that anyway to compensate for the shutdown of nuclear plants, new electric vehicles etc. Some warning for grid stability is proof that solar energy is really working and capable of providing a substantial amount of energy. The old grid and the people have to learn how to deal with it.

Subsidies also kept prices high as manufacturers marked up accordingly. If a new coal fired plant is built then new grid connections and stabilising are required, where is the difference to solar?

NAOM

Well, if I may refer to wind at sea for the Netherlands then gridoperators are required to provide a connection to a new coal plant while a windpark at sea is to provide it's own connection. There is no level playing field.

"one tenth what Americans are spending on our wars."

It is easy to criticize the subsidies for renewables. What about the subsidy for oil. Is there any doubt that we would not have invaded Iraq if they had no oil. Do we really need 11 carrier groups to defend the import of Ipads from China? If the United States was not dependent on imported crude oil from the Middle East I suspect our response to that region would have been "pox on all of you".

That is only the money equation- how many American lives are lost protecting renewable energy?

We can choose to spend subsidies on PV (EROI<10), wind turbine (EROI=20) energy efficiency (EROI=10-100). It seems to but the choice is obvious.

No doubt, wind turbines have their advantages and the bulk of renewable energy will come from wind turbines (at least in regions that don't have excess hydro power), however try building loads of wind turbines in densely populated areas and see how many protests of "Not in my backyard" you will get. Now try the same with PV and notice the much higher acceptance of PV than wind power in a neighborhood. For low density countries, that might not be such an issue, but in higher density areas it is.

Furthermore, PV and Wind actually have somewhat of an anti-correlated performance, meaning that if you build both PV and wind, you need less energy storage. It was calculated in some study (unfortunately I can't remember the link) that the optimal (cost efficient) ratio is about 4:1 wind:PV in Germany, halving the need for storage. That ratio is likely to vary from region to region depending on wind and solar resources.

Yvan;
The Choice seems clearly to have a reasonable blend. Monochromatic positions are pretty brittle.

Your position on this thread has been quite narrow. EROEI is one important measure, but it is certainly not All-important.. PV, Solar Heat, Wind, Hydro, Efficiency.. all of these are among the important tools we can put into the mix.

To keep coming back with this line that calls PV 'a crime against humanity', is pretty extreme and such blinders are not going to be useful if things get dicey ahead.

Some days, you've got Sun and no Wind..

If I put a PV system in a place where most of the electricity comes from renewable outside PV, I create more pollution per watt and I waste a lot of energy. That's it. that's all. EROI is very important. This is why biofuel are an horrible "solution".

I am all for sustainability. Actually, this is my day job (you can easily check this). For me it is clear that many "green" technologies are not green at all and only displace the problem further down. As I said, PV might be interesting in 10 years but not now.

You are making the assumption that the marginal demand will also be 97% renewable. If your locality has excess renewable just waiting to be tapped, and the political/economic will to tap them as needed (say unused hydro), then your argument is valid -for your very unusual locality. A more responsible position would be to build as much of those cheap-easy renewables as you can, and export the power. Unless you are on an island far from a power export market (Iceland perhaps). But for >95% of the planets population, those conditions do not apply.

"As I said, PV might be interesting in 10 years but not now."

So, we just remove all PV incentives, feed-in-tariffs, tax credits, and loan guarantees? No more taxpayer-funded research or project development? We just shelve the whole idea, sit on our hands, and wait 10 years, at which point solar PV suddenly becomes "interesting", and makes sense? What performance-boosting, cost-saving properties does a decade's time impart on the semiconductors?

Someone needs to call Intel and tell them they should stop paying exorbitant salaries to all of those useless PhDs and technicians, and shut down their R&D labs. If they simply wait ten years, their processors will be 30 times faster that what their trying to sell now!

It becomes the same argument wrt. externalities. The systemwide benefit from location X choosing a renewable tech, is largely in the advancement of the technology, which is indirect, and diffuse, i.e. a future PV buyer in Malaysia is as likely to benefit from the externality as a resident of the jurisdictation paying for the presnrday system. So the resident/voter will often take the local only view (it must be cost effective for me), and that is far more restrictive than the globally optimal decision.

But, libertarians, don't care about global optimality, merely what is best for me right now. They are offended by the possibily they may be providing someone else's free lunch. The rest of us don't care so much, as we benefit from lunches others have paid for, and figure it will all come out in the wash.

"If I put a PV system in a place where most of the electricity comes from renewable outside PV.."

You are building your whole argument on a very big and faulty IF, Yvan. How does this apply to the rest of the world? There are VERY few people who can boast of grid power with that much clean electricity, and many places where PV would directly replace Generators, Lamp Oil, Coal Fired power.. and they would be interesting TODAY, and have been already for DECADES.

I just don't see your point at all.

EROI is very important. This is why biofuel are an horrible "solution".

Yet more slipshod reasoning.

Biofuels are a horrible fake solution because biofuels directly compete with food for people to eat. Attempting to grow crops for both food and fuel drives us further and further into diminishing marginal returns, driving up the price of food.

Biofuels pursued aggressively will cause people to starve.

That is why biofuels are horrible. EROEI has nothing to do with it.

No, EROI has all to do. Without subsidies biofuel could not compete with food due to their abysmal performance.

If I put a PV system in a place where most of the electricity comes from renewable outside PV, I create more pollution per watt and I waste a lot of energy. That's it. that's all. EROI is very important. This is why biofuel are an horrible "solution".

You are mistaking the effects of energy payback time for the effect
of energy balance. This assertion can be clearly demonstrated by
considering an extreme case of a very long energy payback time. Suppose that a renewable energy source has an energy payback time of 25 years and a lifetime of 1000 years. If a culture existed which has sufficient patience, longevity, and a huge energy subsidy from some other source, this technology could eventually provide economically useful energy. Assuming uniform installation the long term equilbrium requirement would be to replace 1/1000 of total generation capacity each year at an energy cost of 2.5% (EROEI=40) of the total output. The problem is that this equilbrium would take a hell of a long time to establish. If one wanted to rapidly transition from a 'dirty' source of energy this tecnhology would be useless. However, the reason for its uselessness is its long energy payback time, not its low EROEOI.

Of course it is true that if a number of different renewable technologies have approximate the same life time and their energy costs are primarily in the form of up front expenditures rather than in O&M expenditures, then energy payback time is inversely proportional to EROEI. This is apparently the effect you are thinking about. However,I think greater clarity is achieved if the one uses correct physical parameter which is driving the need for large energy subsidies.

Even in the case of energy sources with relative short payback times other economic factors come into play in addition to energy balance. Consider the case of ethanol produced from sugar cane or corn which you condemn on the basis of low EROEOI. For such energy crops the economic kicker is the opportunity of using agricultural land for food rather than for fuel. Of course energy balance does play a role since the lower the net yield per hectare the higher opportunity cost associated with land use. However, if one considers the gross yield per hectare for a fuel
like corn ethanol, it is clear that even if the energy input requirement were reduced by a large factor (and thus EROEI increased by a large factor) the opportunity cost of land use will still be too high to allow this fuel to replace petroleum based fuels.

Yes, you are right. Payback time is a significant part of the equation to. Especially in rapidly growing industry.

I create more pollution per watt and I waste a lot of energy. That's it. that's all. EROI is very important.

You understand that pollution and EROI are different issues, right?

As has been mentioned already in these comment's most people don't live in places where most electricity comes from renewables. How are most people going to live in such places if they are not installing PV? Please think about that.

The German feed-in tariffs cost them about \$15B a year, one tenth what Americans are spending on our wars.

The military budget for 2012 is between \$1.030–\$1.415 trillion NOT including the classified intelligence program!
http://en.wikipedia.org/wiki/Military_budget_of_the_United_States

Death from terrorism is not even in the 14th most probable American death causes and yet the US spends more on its war on terrorism than to protect against all other more probable early death causes combined:
http://www.benbest.com/lifeext/causes.html#data_usa
Besides, reducing the dependence on oil imports is anyway a better protection against terrorism than protecting oil interests militarily in the middle east.

"The military budget for 2012 is between \$1.030–\$1.415 trillion NOT including the classified intelligence program!"

Sorry, that is an incorrect statement. From that same wikipedia page, the DOD (Dept. of Defense) budget is only about \$680 Billion (1/2 to 1/3 what you quote). FBI, NASA, etc. is not part of the DOD.

Death from terrorism is not the prime issue, disruption of the economy is.

I agree, we should not be dependent on foreign oil whether it comes from Canada or the Middle East or wherever. Just get the Govt & the environmentalists out of the way so we can develope & use the resourses we have...that includes the rare-earth minerals we have but can't get to because of regulations/litigations & must be dependent on China & other foreign mineral suppliers for out 'green' (which is actually brown...but we won't go there) economy.

CIA, NSA and all the classified private intelligence agencies are certainly a big and very costly part of the war on terrorism: http://projects.washingtonpost.com/top-secret-america/

Death from terrorism is not the prime issue, disruption of the economy is.

Which is also why it makes even more sense to invest in the reduction of the dependence on limited, very price-volatile imported resources (and thus very economy disrupting) instead of uncontrolled privatized but tax-payer paid intelligence agencies.

that includes the rare-earth minerals

Actually, geared wind turbines (which are the majority) don't use them and even gearless, direct-drive wind turbines from Enercon don't use rare-earth metals: http://www.enercon.de/en-en/1337.htm
And PV also runs without rare-earth minerals.

Just get the Govt & the environmentalists out of the way so we can develope & use the resourses we have

Actually, Germany has more govt & environmentalist influence than the US and yet exports more than the US and Japan. And Somalia has no govt & environmentalist influence and produces and exports not much (if anything).

Actually, geared wind turbines (which are the majority) don't use them and even gearless, direct-drive wind turbines from Enercon don't use rare-earth metals

The decision to use a generator utilizing RE magnets depends upon the price/cost calculations. REs can make more compact and efficient generators, but if their cost is too high, because of RE scarcity, then the somewhat less efficient alternatives are used. I.E. wind isn't hsotage to RE, although if they are available at low enogh cost, they help it.

Just get the Govt & the environmentalists out of the way so we can develope & use the resourses we have

The problem was that China priced the existing non Chinese sources out of the market, then decided to play hardball. If the government had declared these resources to be critical, it could have mandated that mines stay open (and customers or taxpayers make up the difference).
In a pure free market system, you are vulnerable to others playing monopolistic games like the Chinese did with REs.

He also forgot about the Department of Energy, specifically the National Nuclear Security Administration (NNSA)

http://nnsa.energy.gov/

I consider the Department of Homeland Security (DHS) part of the U.S. Military Industrial Complex (MIC).

NASA has historically funded projects which were potentially dual-use.

The STS (Space Transportation System...Space Shuttle)specs were influenced by the DoD.

DoD even built a Shuttle launch facility at Vandenberg AFB, never used for a STS launch.

The current DoD X-37 started as a NASA program.

Follow the money...the MIC is a little more pervasive than many folks think...

Thanks for bringing this article to our attention, Rembrandt. It brings some balance to the technical discussion, and reveals an ethical/moral dimension underlying the attempt to develop alternatives.

IMO our civilization should be encouraging the shift to renewables like solar and wind on a much more serious scale - if for no other reason than it gives us more time to adjust to higher fossil fuel costs and supply declines. I agree that demanding magical levels of efficiency for PV is intellectually shallow, but I understand how a depressed doomer might see any attempt to cope as pointless. I think the problem with expanding PV is rooted in the same overall inertia of the system that hinders effective response to sudden economic shocks. It's just being honest to note that the speed of the coming shocks to the system may well overcome adaptive strategies.

Nonetheless, I feel we should be ethically motivated to try to advocate good ideas for coping with our conundrum and simply behaving in a calm adult manner to try and make our transition to lower free energy less chaotic. Encouraging PV and wind definitely fit that strategy.

I think there is great value in doing SOMETHING, regardless of the ultimate efficiency or efficacy. Yes, you should make good decisions and try to do what is technically the most sound, but don't get lost in that analysis. I know full well that what I do on a personal scale may not make a wide scale/long term difference, but I have no doubt that my actions and attitudes have an effect and value.

If the ship is sinking, do we need deck officers who are fighting amongst themselves or even creating panic, or ones disassembling floatable materials that might save a few lives, or just offering simple compassion? Even the orchestra on the Titanic was performing a laudable psychic service to the passengers.

Yes good article. There are many ways of looking at this and simply reducing the debate to 'its EROI is less than 10 and worse than wind therefor all we should do is wind' is not particularly helpful. For a start in most urban environments, at an individual level wind is a non-starter; our local council would not touch wind when we approached them about a home installation but welcomed solar with open arms. They already have a zero fees application process for planning application for solar thermal and are only too willing to extend that for PV. Here in New Zealand there is ZERO subsidy for PV generation (the electricity company will simply credit you with a 1:1 credit on power generated), so the economics have to make sense at an individual level. I modelled this is several ways but one of the most convincing arguements I came up with was this. The cost of our fully installed system (3kW grid tie) was \$NZ\$22,000. In the first year of use it would (and is) generate \$1350 of electricity savings. We had the NZ\$ 22000 available sitting in the bank. As in almost every other country interest rates here have been slashed (and have been ultra low for 2 years with absolutely no sign they are going to improve) so the best annual interest available on that sum is 4.5% or NZ\$990/annum. After tax that is reduced to approx \$740.

As against \$1350.

No contest what I should do with the \$22000 was there?

Then throw in the fact that annual electricity rises in NZ have been of the order of 7% per annum, so that \$1350 in savings doubles in 10 years.

Then throw in the fact that the buying power of the original \$22,000 is being now constantly denuded by inflation/currency devaluation (yes we are involved in a rush to the bottom as well).

In 10 years time I would guess the buying power of that \$22,000 would probably be halved.

So hell I dont really care if the EROI of my system is 7.5 or 8 or 10.

I just know that it makes a ton of economic sense AND in my own small way I am doing something.Our electricity bills have effectively been abolished and so now our only external cost for the heating/running of our home is the propane gas cyclinders we use. The cost of those comes in at NZ\$300 a year, and that has become the TOTAL energy cost of running our home (there was already a pre-existing solar water system fitted to the house when we bought it). Ours is not a small house - 250m square (including workshop garage).

Wind is not viable here, the wind speed is too low. On the other hand we have a lot of sun. Given the seasonal nature of our rain we would get too much or too little and require a large storage capacity. Electricity prices will only go north so it makes sense for me to add solar into my equation. Oh, traditional electricity generation here is subsidised.

NAOM

To all: Where does one find the best ROI solar panels to buy directly from either a manufacturer or wholesaler? Im interested in buying into solar but the prices here are pretty poor compared to over the seas.

Yay another Kiwi!

So which part of godzown do you live? Im from Papamoa.

G'day squilliam - we are in sunny Nelson.
Its your lucky day - Powersmartsolar NZ just sent me their latest deals on panels with prices slashed (sob - cheaper than I bought 12 months ago, ah well)
3kW system now NZ\$15,250!!!
Go to www.powersmartsolar.co.nz
(and tell them Andy Hamilton from Nelson sent you, LOL)

That's pretty decent ROI. I did the maths and it'd make approximately 5.5% per year at the current mixed rate here of 20c KW/H. If I do go with them i'll definately tell them you sent me since it'd net you \$150 referral, right?

However I can't help but think if I imported the cells myself I would get an even better ROI if I sourced directly from China or the U.S. I was thinking of doing a group buy for people in neighborhood.

Yvan, do I gather that you live in Canada? Which part? It is relevant as Canada's generation portfolio differs widely with geography. You may be one of those enjoying hydro, or you might be burning coal...

Which impinges directly on the second question: why in the world are you heating with electricity? You seem far too well-informed to heat with coal-generated electricity, so maybe I've answered my first question. Either way, in Minnesota we call that...ill-considered. What do you know about solar thermal? =)

Every method of generation does harm to our environment somewhere along the chain. Yup, hydro too.

As I said, in Québec, electricity is 97% renewable. We are heating with electricity because I can do it. The original system was using an oil burner, we have installed a electric heater in the furnace. I know it is completely stupid to heat your house with electric resistance. I have checked heat pump and geothermal and the make no sense in my case either financially or ecologically.

What I to improved the overall efficiency did is install new windows triple glaze with argon one layer of low e in south two layers in north. I have also largely expanded the windows area in the south. The stupid architect who has designed this house in 1957 has put the largest windows north and the smallest south!!Not much money wise or ecologically wise since the old windows could have survived many years, which means I have loss their embodied energy. However, I have a much livable house now. I have also largely reduce air infiltration. It is down from 5 changes per hour to 3. I could probably do better but this would be much more difficult. Now in sunny days my house can heat itself down to -10C in winter. I still need to add more windows on the west side but we are still arguing about the improvement of this side of the house.

As for hydro, it has one of the lowest environmental footprint per kWh. Clever energy design are always better.

The most environmentally good that could be done with Quebec's excess power, would be to export more of it. A financail and environmental opportunity cost is being paid by making power so cheap that residents use it for low value applications like resistance heating. Of course being a good global citizen, and being politically feasible may not be the same thing.

Well, it is not that simple. Unlike oil, electricity is a local market. Hydro-Québec could swamp the New England market with electricity if they wanted to. The problem is that would make to price drop like a rock notwithstanding the problem with the US grid. Building new dams become more expensive has they are further out at the same time electricity price for exportation does not follows the same curve. There is a political movement here asking we raise the rate here to export more in USA. This makes little sense for the above reasons. In practice, consumption elasticity is rather low. Outside heating, we consume no more electricity than any one in North America. Indeed., there is some indication that the average house is more energetically efficient than in Ontario.

The whole economics of the electricity exportation is based on the gas turbines operation. If gas turbines do not start, the price is not interesting for Hydro-Québec. So we have to export just the right amount of electricity to insure that gas turbines stay in operation.

Otherwise, the best idea is to bring industries here to use our cheap and clean electricity. It creates much more wealth for us and still save the planet.

There is also a learning curve argument. If solar farms may be important in the future, building a few small ones early on -even if not strictly cost effective is a good way to provide the seeds (local experience) for a possible future expansion. Its kind of like paying for a college education, I don't make money paying for a class, but hopefully a few years from now, it will open up opportunities for me. A few small loss-leader projects make sense, because they can set you up to take advantage of an uncertain future opportunity.

I have checked heat pump and geothermal and the make no sense in my case either financially or ecologically.

Ductless heat pumps are relatively inexpensive and perform surprisingly well even in our cold Canadian climate. Our Sanyo 12KHS71 works down to -22°C and generates, on average, 2.75 kWh of heat for every kWh consumed (in southern Québec, the ratio would likely fall between 2.3 and 2.5:1). There are systems that are notably more efficient such as the Fujitsu 12RLS and others that continue to crank out a good amount of heat at -30ºC and below, e.g., the Mitsubishi Zuba.

Bear in mind that you don't require a system that will satisfy all of your space heating needs; even if it displaced just half of your total load it could still prove cost-effective.

Cheers,
Paul

I know all that. We have now 20 graduate students who are working in the industry. The problem, is that payback time can be calculated in decades in my case. Saving energy for saving energy can only be an illusion in some cases. Many technologies would made sense if they were implemented when the house was build but make no sense in a retrofitting. In my case, roughly half of my total load is heating. Hence, we are speaking of something like 20-30% reduction in the bill, which is marginal for the money involved.

I highly doubt the payback would be "decades" as you claim. You mentioned above that your electricity bill is \$180.00 a month or a little less than \$2,200.00 on an annualized basis. Using your estimate of a 20 to 30 per cent reduction, the potential savings would be presumably somewhere in the range of \$400.00 to \$650.00 a year.

I recently purchased a second Sanyo 12KHS71 for a little less than \$1,500.00 and, installed, my final cost will be perhaps \$1,800.00 which based on your numbers suggests a simple payback of about three and a half years (for me, the payback will be less than two). Even if the installed cost were twice that of my own, we're still looking at a ROI of about 15 per cent assuming that electricity rates remain constant for the full duration of this time; by comparison, my Bank of Nova Scotia shares generate a ROI of approximately 4.1 per cent.

Cheers,
Paul

Well, I got phone call from heat pump seller 2-3 times per years. Normally, conversation stop when he know the value of my electricity bill. Installation cost is often a killer, since it is the profit margin of the seller. Actually, my electricity bill for heating alone is roughly 1000\$/yr. Hence I would save 200-300\$/yr and get a 6-9 yr pay back. I guesstimate the EROI to be around 20, which is rather good (It competes with the additional glaze on my windows.)

At first sight, this make not much sense for me. Nevertheless, this product possess some nice feature. I will tried to get more information on it.

Thank for the hint.

You're welcome, Yvan. Our electricity rates are double that of Québec and our climate here on the east coast is quite a bit milder than your own and so we benefit on that end of things as well.

Our average hourly temperature: http://i362.photobucket.com/albums/oo69/HereinHalifax/CA.jpg

Our home's space heating demand beyond the waste heat generated by lighting, appliances and plug loads (as best I can determine): http://i362.photobucket.com/albums/oo69/HereinHalifax/CB.jpg

Actually, my electricity bill for heating alone is roughly 1000\$/yr. Hence I would save 200-300\$/yr and get a 6-9 yr pay back.

It could be a little better than you think. Assuming you could satisfy 70 per cent of your annual needs at a seasonal COP of 2.4, say, your savings would be closer to \$400.00/year.

Cheers,
Paul

" Hence I would save 200-300\$/yr and get a 6-9 yr pay back. "

That was my calculation too. The kicker was that I could get AC too. That is hard to put a value on as there there was none before, but even if you just consider the cost of a simple AC only unit, that is extra money I don't have to spend for a given benefit, or an extra benefit for the same money.

and umm where do the people get the 25 to 30k it costs to put such a system in place per roof?

Presumably from the same (or similar) place they got the money for the lot and the house (including the roof). Which together is more costly than the PV by a factor of 10.

Hint: it starts with "B" and rhymes with "sank"

Are you asking where do they get the money? (Previous poster addressed that)

Or are you asking where does the \$25K to \$30K estimate come from? That estimate comes from your local installer as to how much a typical residential system costs.

yes i am asking where does the average person get the money or get someone to loan them more then they make in a year for something like this. most banks won't now a days, and saving up for it is not a option unless you like waiting over a decade. which considering the time frame involved makes it a non-starter.

pv, as nice as it is. is only a rich and well off person's toy. used to say 'hey look i am green' but ignoring all the 'non-green' stuff involved in making in and the needed oil infrastructure needed to make and maintain it. I have heard these things called fossil fuel extenders because they still require them, but not as much as the current system. for the average person now, time and money would be better spent preparing for the days when electricity is either not available. or only available for a short few hours.

in a better world this would be required equipment for houses to at least partially offset the energy use to a cleaner but not completely clean power source, and in the process create demand for it and thus a market where companies can thrive and hire employees and all those nice things a economy needs. putting aside the whole 'we have to get away from growth mentality' that is needed for the situation.

TK,

Perhaps start small and modular, and add as time and money permits, in a DIY fashion.

The smallest way I can think of is a single PV panel attached to a single PV microinverter (enphase or such), in a grid-tie setup.

Just leave space to eventually get up to around 1kW of peak power, and that should do quite well to reduce your total grid kwh and peak kw grid usage.

For projects of how others do, perhaps reading up on a DIY magazine like Homepower magazine

Good point, but You can start with 1 panel ( ONE SKU + Mount ):

http://www.auosolar.com/?sn=784&lang=en-US&c=238

Note that the Grid Tie Product ie. Panel/Connector harness is Listed to UL1741 as a ready to rock "MODULAR SYSTEM" - No fussing around with mounting micro-invertes to a rail, No separate grounding conductors, No fire code ground fault requirements, etc - The ground path is thru the LOCKING wiring harness. Grounding is a major cost in US Installed PV Systems. Just 4 Panels = a Kilowatt. This a a true 240Volt AC Panel -Inverter is Solarbridge from Austin Tx.

AOU is Acer - The Computer/Display company, Something like 14 Billion USD in flat Panel displays last year. If PV Panels follow LCD's scale/pricing, expect \$1 watt shortly. The major cost of PV is the wafers, and production of wafers is scale-able. So, in addition to the Chinese, we now have LG, Samsung & AOU in the global PV race. Since the Chinese now have aggressive Feed-In's - will we see some ELM Solar Panel effect??

On peak efficiency is Sunpower, who has the Patents in the US for back contact connections. This is the true Black-on-Black Panel, no conductors on the cell fronts to block light, hence the 200 watts per square meter outputs. Sunpower's offering is dealer only installed turnkey system, all the way to the mounting, Innovations include quick install time on the roof with self sealing expanding anchor bolts, so it's not necessary to spend hours locating rafters. French Oil Giant TOTAL is now majority owner of Sunpower shares as well as many other Solar companies. http://us.sunpowercorp.com ... The Solar business reminds me of the Microcomputer industry in the S100 BUS/pre IBM PC days.

How much do those cost?

IIRC Unison product MSRP ~ \$3.00 +/-15% per watt range, depending on order size. Certified turnkey Installation in the \$4.50-\$5.50 watt range, expect .35-.50 watt premium for micros, which often is made back in reduced Install costs. Not a lot of competition yet in the MicroInverter space, Enphase shipped the 1 millionth micro, bet that many flat screens get dropped daily. If you want more feedback on the product, my contact info is in TOD account info, I will have 1st hand experience with it soon.

You save a reasonable amount of \$\$\$ on the cabling as well given they are AC and not DC right? Also I take it you can scale the system as needed without having to worry about over-sizing relative to the inverter?

AC panels you can add one at a time. DC Strings locks you in to a custom design for each roof/panel/Inverter/Local and best to be designed by a Solar Pro.

1. Cheaper wiring, DC must be in Metal conduit or MC once it enters the house
2. Individual panel monitoring of Power Harvest
3. ALL Panels don't HAVE to be at the same angle and in 100% clear 365 days/year.
4. Possible deploy where you would not DC Strings.
5. If you have an issue with one panel, bird droppings, etc it's no big deal.
6. Modular, add a panel a month.
7. Safer, 240 VAC is less than 150 volts to Ground.

1. higher equipment cost.
2. more failure points on the Roof.
3. No good Backup power solution yet.

The modularity alone is enough to make it seem quite advantageous so long as the additional cost isn't crippling. I don't see the lack of battery backup as a problem since a generator is probably more cost effective in case of any real power loss compared to batteries.

I don't know if the on panel inverter is modular enough to swap out without swapping the panel. I would see that as an advantage due to the difficulty and waste of swapping a whole panel that may be a different size in 10 years. If the inverter cannot be swapped with the same or different make then I would see that as a downside.

NAOM

The examples I've seen from emphase examples were modular, but it would be an obvious issue if these were monolithic.

Mind, I was talking to a PV installer the other day, and he was saying the single string inverters he was installing had a 5 year expected life - then you had the significant issue of replacing that at high expense, etc.

Worth checking what the warranty covers - seem suspicious so many seem to be for the panel, not the rest of the electronics.

That sounds worrying and what I was worried about, thanks.

NAOM

There are also things called DC optimizers, that are cheaper than microinverters. They are supposed to reduce the power loss from mismatched modules on a string. In case you don't know, panels act like diodes, the one producing the least amount of current (perhaps cause its shaded, or maybe is hotter or whatever), determines the current output for the entire series string. So one bad apple essentially ruins it for the whole bunch. But DC optimizers are supposed to reduce the effect.

So you have three ways to go, in order of lower to higher efficiency, and also of lower to high cost.
(1) string inverters.
(2) string inverters, plus DC optimizers.
(3) microinverters.
Discussions at GreenTechMedia came to the conclusion, that except in certain shade challenged applications, that (3) would not be economically competitive about 2.5 to 5 KW.

http://www.gogreensolar.com/products/sunmizer-dc-power-optimizer

\$312 Per Panel. Not exactly what I would call cheap. Oh there is one from ecodirect \$210

Forget those.

Look at Tigo (~\$40 per module), or Solaredge (~\$100)

For reference, Enphase is a little under \$200 per module with cabling.

Which string inverter has an expected life of only 5 years? E.g. SMA is guaranteeing 5 years with the option to extend to 10, 15, 20 or 25 years. Perhaps you mean 5 year guaranteed life?

I don't know if the on panel inverter is modular enough to swap out without swapping the panel.

They are modular enough. They will probably still be modular enough even when true AC panels start hitting the market. The inverter will be to the panel as, say, the battery is to the laptop.

The National Electric Code defines an AC panel in a way that precludes any exposed DC wiring. No such product has actually been released yet. I know of only one company that is actually selling the micro-inverter and the panel together. Mostly they are still sold separately, and buyers can save more money that way.

that's still about 4-5k. you do realize at least in the united states the average person has less then 10k in the bank? it's amazing and i am a bit flabbergasted at people throwing stuff like this around as if this amount of money is NOTHING. for that amount of money i can add extra living space to the house(by finishing off the rest of the basement) i am in to let the rest of my family live together thus being just as good to the environment by wasting less space. i could put a sizable down payment on higher mpg standard car or diesel. i could fix up the house to use the two fireplaces it came with. any one of those things would be a better use and over the long term a better buy with that amount of money..

Think of PV as the chocolate sauce on top of a Sunday, but don't under estimate the reduction in heat gain by shading a south facing roof in Southern climates. On a ranch style house I was able to replace a 3 ton central AC with a 1 Ton ductless after installing just 10-250 watt PV Panels. I have a TED5000 energy monitor on both the PV and the AC, For Summer season just 5-6 Panels will net out the energy use of a Fujitsu 12RLS that is running 24/7. Savings in 2-4 years will pay for the PV.

in which case since it's a apt analogy. what your doing right now is taking that same sunday, and eating it in front of a hungry person while he is being held down to prevent him from taking it from you. you talk of toys like this casually and talking about repayment of a investment as if it was a universal law that it will happen, when the prospect of the system due to greed outside of the physical reality looks shaky enough to not last that long.

just sit down and think for a minute, look around you and see how lucky you are. your either part of the top 10% of this countries people. or your a pensioner who is lucky enough to not have very many if any medical issues at all that you can blow your retirement money on stuff like this. and here you sit, and i have no better word for it but sheer ignorance and gall to suggest that someone should go into that much in debt. Just so they can see a 1/4 to 3/4s reduction in monthly bills for electricity. when there are much simpler and cheaper ways of achieving the same result and are more sustainable. shade that side of the house with tree's or other foliage. if you live in a southern climate you don't bleeping need a heater as long as it doesn't get past freezing. better insulate your house past the stucko and plywood walls. in the summer wear a set of very light clothes around the house and put your a/c on 77-80. if you need air circulation use a few small fans rather then the whole house system as they will use less power.

TK.
There are ways to essentially lease your roof to a PV company in turn for a power purchase agreement, which is lower than your current grid cost. The name that comes to mind is SunRun (not an endorsement), but there are roughly a dozen companies in this space. Essentially the homeowner owns, the roof, and the PPA, which is sold along with the house. I think these arrangements are typically no (or little) money down. I get the impression at least half of recent residential installations are done with these sorts of agreements. So capital straved homeowners can still (somewhat) get into the game.

If one does not have the cash:

1. Buy one PV panel at a time and build up your system over several years reducing the initial expense.

2. Get a home equity loan.

3. Get a job installing photovoltaic systems which would allow you to install your own grid-tied system.

At SolarCity we believe clean solar energy should be affordable for everyone. That's why we created the groundbreaking solar lease option SolarLease®, a way for homeowners to go solar without any upfront cost and save money from day one.

I wonder what happens when those lease companies go bankrupt. Does someone come along and rip the panels off your roof and leave them in a pile of junk? In bankruptcy those companies goods often get sold off for ridiculous prices, would the panels that you have been relying on end up on EBay being sold off to someone 4 states away for a few dollars?

NAOM

Not a bankruptcy expert, but I suspect the systems come with a contract. That contract is a revenue stream for whomever holds it, the homeowner is paying for the power. It would be in the interest of whomever acquires these contracts to keep the systems functioning and the checks coming in. The major cost for the contract holder is the intial capital expense, operational expenses are easily covered by the power sales, and the cost of ripping them up and selling them for scrap wouldn't make that attractive (except maybe if the house is in foreclosure).

I wonder what happens when those lease companies go bankrupt.

If that should happen, you could probably buy your system at a firesale price. These lease agreements all have market value buyout options that you can take down the line, sometimes more than one depending on how old the systems is. And if the reason they go bankrupt is that the economy collapses so much that all their revenue stops, well ... it's Mad Max time, get a gun and defend your roof. ;-)

As a customer, I'd be more worried about them taking away my panels if I go bankrupt.

Anyway, you should ask yourself why they would go bankrupt. Say you're one of these companies in a decade or so. You have a very steady stream of revenue from everyone paying off their panels. You have a ton of panels on people's roofs that are actually your assets, that you could sell to them to generate quicker cash if you need to. At some point you may be able to finance all your new lending with your revenue stream. It's as good a bet as anything these days.

Finally, I'll let you in on a secret. The reason these lease deals are so good for everyone (except the government?) is that the company that 'owns' your panels gets to take a tax break on the depreciation of the panels.

Thanks for the input.

NAOM

and umm where do the people get the 25 to 30k it costs to put such a system in place per roof?

Well, for people who don't have it in the bank, there are now a number of companies offering solar lease options that reduce the initial money down to hundreds instead of thousands.

It seems to me (admittedly before coffee) that at this point in time, fossil fuels are mostly extracted & burned to create "jobs" and "economic growth" rather than doing things that actually need doing.

ER/EI is fundamentally important as a concept looking into the future, when it will once again become the determinant between life & death as it is for any hunting or foraging species. It's a crucial concept. But we ain't there yet in any critical sense. We're mostly building stuff we don't need, creating roads we'll never be able to maintain, and treating "jobs" as intrinsically valuable, as though they were something other than an ad hoc evolved distribution system for fossil-fuel largesse.

Any fossil fuel that comes out of the ground now will be burned. Building or not building PV won't alter the flow rate. About the only thing that seems to throttle the flow are economic downturns (and surrepticiously triggering those represents the low-hanging fruit for climate activists, if they ever figure that out).

That being the case, we might speak of "future utility from energy otherwise wasted" (FUFEOW). Under this metric, building Alan's railroads, or a bunch of PV, in the near future simply replaces X amount of idiosyncratic crap which our current economies would otherwise generate.

Seen from the point of view of our immediate descendents, railroads and PV could be quite useful. Durable things with utility, what a concept. (Of course, most PV made now will be nonfunctional in 100 years; though it might be interesting to look at designing it for 500 or more).

From the point of view of other species and the planet, PV makes little difference. It's something we'll do in addition to burning what we can reach. But I think it should be done, along with windmills and as nontoxically as possible, if only as performance art, and I'm doing so at my home. It's aesthetically cool, like giant stone heads. It's workable magic, for awhile.

Compared with a giant stone head, a bass boat, or a McMansion, 15% energy conversion efficiency kicks butt. It's way to tap directly into the fusion energy that created us all, in realtime. It's amazing that we can make them as well and as easily as we can.

Building PV in 200 years will be a whole 'nother thing. The stone heads may outlast the last solar panel by a good margin.

I love the FUFEOW concept. That nicely summarizes why I think even doomers should support renewables. One can also hope that the infrastructure and cultural inertia developed in redirecting that energy to renewables now might be a little more durable than the renewable generation equipment itself.

Performance art; I love it. Evidence of intelligent life in the universe, thanks, Greenish. Except that even as performance art, it gives folks the wrong idea that technology is going to save us and that we can one-up Ma Nature because we're so clever, all the while making a stinky pile of pollution and mining mess in other countries that make our panels (and batteries). If I can't get railroads, I'll opt for a real-deal stone head as a reminder of where we're headed, if this set of comments is any indicator.

You're right that real stone heads would likely be the less harmful option to the planet, and thus to all humans past 2-300 years from now.

Cushioning the next several generations from suffering the effects of our industrial fossil-fueled overshoot really is at odds with minimizing harm to the planet. It's an uncomfortable truth.

If it's desirable for humans to continue to live on the planet in reasonable numbers for the next half-million years or more, probably the best thing would be an immediate human catastrophe of some sort, a very abrupt cold-turkey cessation of fossil-fueled industry and drastic diminishment of human population.

If it is NOT considered important for humans to live on the earth more than a couple hundred years, or for other extant species to do so, then we should keep burning stuff. That is what "feels right" to our monkey brains, which have a hard time with "the future" past a week or two down the road, and don't have faces to mentally put on future humans.

Currently, it is not considered actionably important for humans or the planet to survive; we're content to be self-boiling frogs. This basically nihilist/hedonist course is considered normal and right by the vast majority.

My suggestion to incorporate performance art (including PV) into the nihilist/hedonist majority lifestyle should be taken in that vein. It's probably no worse on average than whatever would be made by the fossil slaves otherwise, and will allow us to continue metaphorically fiddling while Rome burns.

I'm not unsympathetic to those who wish to maintain the illusions awhile longer, and PV will probably be good for that.

My main sympathies, though, lie with the denizens of post-bottleneck earth; those unrepresented humans and species who could populate the next hundreds of thousands or millions of years. Whether we build PV, stone heads or gaming computers now will make little difference to them; their fate - if not already sealed - probably lies in how soon a deep collapse comes and little else.

Still, I have PV on my roof, and I'm not ruling out a stone head or two. Because it is performance art.

Fire & dopamine, that's the game.

Nice post greenish. I'm going to repeat the part I liked most.

we might speak of "future utility from energy otherwise wasted" (FUFEOW). Under this metric, building Alan's railroads, or a bunch of PV, in the near future simply replaces X amount of idiosyncratic crap which our current economies would otherwise generate.

Oh . . . some snobbery is needed. If you have a residential home and you want to power an EV and your home with solar then you probably can't go with low efficiency thin film since you'll quickly run out of southern facing roof area.

But yeah, the current generation of silicon panels are just fine. Thin-film is great too . . . but you'll need a bit more area to get the same amount of power.

If you have a residential home and you want to power an EV and your home with solar then you probably can't go with low efficiency thin film since you'll quickly run out of southern facing roof area.

A lot of people probably have enough south facing roof to power an EV and their home with today's products. Not most people, but a lot of people. A percentage of the population that numbers millions in this country.

At some point 'large south facing roof, no shade' will start to appear in real estate ads.

The needed breakthrough is in batteries, not PV. To meet winter demand every house roof could carry 10 kw of PV with say a 30 kwh battery pack. That might help get through a blizzard for a couple of days if the house also kept a portable propane stove for emergency heating and cooking. Wash your hair with a pot of warm water heated on the camp stove. In heat waves the 10 kw would easily cover a 2.5 kw air con and some output might have to be curtailed if the grid didn't need the excess.

Claims of \$1 per watt for PV don't seem to apply to polycrystalline silicon without subsidies. Suppose it did then 10 kw of PV would cost an affordable \$10k. However the bulk and cost of the battery pack is the killer. If would be great if you could get a 30 kwh battery in a bar fridge sized container, tamper proof, cool to the touch and costing just another \$10k. As far as I know no such battery exists.

We can't wait for breakthrough in Batteries, Me thinks it will always be expensive to store kWh. But now, PV prices are such that we can design with more PV, to minimize the depth of discharge and use smaller, less costly batteries. If ICE can be made as cheap as they are with thousands of specialized moving parts and rare earth metals in exhaust systems, etc, surely quality Crystal Si PV panels can be made for .50 watt. Or not? Never buy panels on price only, you find the market price for quality product, U R making a minimum of a 30-50 year investment. The company making them will not be around.

\$10,000 for a 30 kWh battery array is a bit pricy.

1 Crown L-16, 6V, 395 Ah lead acid battery costs \$304 + ~8% sales tax = ~\$330

14 batteries would store 33.2 kWh for a price of \$4,620.

10 kW of PV would output about 51 kWh / sunny day and about 12 kWh / cloudy day.

That is a big PV system for a house. My house has been running from an off-grid PV system for the last 20 years using 8 L-16 batteries and PV panels that currently output 3.0 kWh / sunny day. How much electrical power does one really need?

How much electrical power does one really need?

For my house, in Southern California, my usage averages out to less than 850watts continuous, unless I made an embarrassing arithmetic mistake somewhere.

That is for a standard home built in 1939, double glass windows, blown insulated roof/ceiling, LED and CFL lighting, but no other 'green' modifications.

Two adults, three kids, watching TV, using computers, and all that jazz.

http://mrflash818.livejournal.com/119672.html

You are using 4 kWh / day / person which is a little more than mine.

"However the bulk and cost of the battery pack is the killer. If would be great if you could get a 30 kwh battery in a bar fridge sized container, tamper proof, cool to the touch and costing just another \$10k. As far as I know no such battery exists."

Our battery, A Hawker Industrial forklift battery set is rated at 52.8 kwh (twelve 2 volt cells, 2200 amp hours at 20 hour rate) 12.4 cubic feet, cost ~\$6600 in 2009. Oh yeah, it's relatively "cool to the touch and tamper proof". Just sayin'.....

Great article.

One small quibble:

the real kicker is that the fossil fuel (or nuclear) plant supplying the electrical power is only 35% efficient for a net fossil-to-wheels efficiency around 25% (same ballpark as the gasoline car).

That doesn't really make sense. At least in the US, EVs mostly charge at night, and night power is dominated by nuclear, where the thermal efficiency doesn't really matter, given how cheap the fuel is. As windpower becomes more important this will become even more true: we don't pay any attention at all to the efficiency with which wind primary power is converted to mechanical energy (and then electrical energy) because the only important costs are the capital costs of the wind turbine.

If you want to take the very long-term point of view, EVs will be charged by windpower, and the conversion from primary energy will become entirely unimportant.

Good points. I agree: my objections completely melt away if a renewable resource provides electricity to charge the EV. And sure, maybe I should heed my own advice and not be an efficiency snob when it comes to nuclear. I would totally jump on board with this view if nuclear fuel were as unlimited as the sun or wind. But it is still a finite resource, so I'll reserve a bit of snobbery on the nuclear heat-engine front.

At least in the US, EVs mostly charge at night,

Source?

If you want to take the very long-term point of view, EVs will be charged by windpower

I think the long term point of view on EVs is that they will charge during the day with solar, because there will be charging stations (with credit-card readers) at just about every parking space. At any rate, that's the only way I really see EVs working without cars continuing to cook the planet. I'm not really so keen on these EVs. Some jobs and tasks will always require driving, but mostly we need to have a culture and society with less driving per person.

The EV will be the credit card. It will take charges and credits, cash payment or power banking.

NAOM

Windpower. Don't forget about windpower, which is cheaper and larger-scale than solar.

One thing concerns me with windpower.

Moving parts.

This alone suggests to me that wind power cannot remain cheaper than fixed-installation PV power over the lifetime of the system, though it is only a gut feeling and I could be wrong.

Well, land-based windpower has maintenance costs of less than \$.01/kWh. That's not enough to overcome lower costs per Wp and higher capacity factors.

Rembrandt,
Your very clear explanation of the limitations of silicon PV efficiency is appreciated. However, like many single focus analyses it fails at the level of its underlying assumptions. For example, based upon your discussion one would conclude that:

1- Surface area is the limiting factor in PV installations.
2- Module price per kw of output is the second limiting factor.

In the real world the Chinese have turned solar panels into a commodity and driven the price downward almost as if they were channeling Moore's Law. Balance-of-system costs are now greater than module costs in many areas. And they are much more resistant to substantial reduction.

With BOS cost the determinant factor in system cost, efficiency IS important. A 450 sq ft residential installation will have nearly the same BOS cost--- amounting to perhaps half the total, regardless of whether it produces 4kw @ 15% efficiency or 8kw @ 30% efficiency. Betting that technology will stand still over the next 30 years is a loosing proposition. If Home Depot offers you the choice of a 18% silicon wafer panel or a 30% roll printed nano-structured multi-junction panel off the shelf in 2020 for the same price, which will you buy?

The only people worried about residential customers producing too much power are the utilities who might be forced to buy the capacity instead of building a shiny new central power plant.

Efficiency IS important, and increases in efficiency will the final nail in the coffin of centralized grid power price advantage. But this doesn't mean that you shouldn't buy a cost effective 15% system today rather than waiting for the future to hit you over the head.

I'll save Rembrandt the explanation that he posted the article that I wrote. This article responds to reactions I have witnessed personally by people who did not understand that efficiency was not a limiting factor for their concerns (i.e., that they had enough roof area).

If the BOS cost is dominant, then the efficiency of the BOS components is surely important, but these components generally turn in 90–95% performances each, which no one will sneeze at.

As for whether to take the promise of 30% efficiency in 2020: I can't remember, is 2020 before, or after an economic collapse? It bears on the decision, which your final statement echos, and with which I agree.

I doubt we will see 30% at decent prices. cSi will run out of gas in the low twenties. And I wouldn't be surprised in the coming superthin wafers (a half to a tenth of the current amount of silicon per square meter) bring down efficiencies. But, heck 22.5% is fifty percent better than 15%, which would be a big deal. There are projects attempting to reach 65% for fancy multijunction stuff, these might be useable for CPV applications.

I've also seen claims about the possibility of exploiting thermal radiation. The flux of thermal radiation is mainly skyward (at ground level)it is roughly half of the incoming solar flux. If this can be added as yet another layer, there is potentially a pretty good boost in output. And best of all, it doesn't stop when the sun goes down [but that 50% figure is an average over 24 hours].

Shec Energy has new CSP and storage technologies. Efficiency at about 30%. Heat storage at 850 degrees C. Rapid parabolic mirror manufacturing.
www.shecenergy.com

If what they say is true, that's very good indeed. Also, puts to bed the oft-repeated remark here that solar thermal is dead as a result of the improvements in PV. Everybody should remember that ALL tech always is improving. We need to look at the basic physics, as Tom Murphy keeps telling us, to see what the limits are. In solar thermal, the thermodynamic limit of efficiency is around 95%. Half of that, what we can usually get, is around 45%, which is pretty good, right?

And the required hardware is simple iron, which we know about.

Besides, efficiency per se, is not it. What is it is whether I have fun doing it or not :).

Shec Energy has new CSP and storage technologies. Efficiency at about 30%.

Interesting technology, but their website is light on technical data.

Note that it is common for Solar Thermal % claims to be based on collector area, and not on site area. The full axis tracking designs like Shec use, have wide spacing to avoid shadows.

It a site can fit in Solar PV, for the same MWh, for less \$, even at lower efficiency it underlines the OP's original point.

contrast that with this news in August

Solar Trust said today that it will convert a 500-megawatt solar thermal power plant it had been planning in Blythe, California into a 500-megawatt plant made from photovoltaic panels.

The shift comes because of "improved market conditions" for building power plants with PV modules.

PV is close to plug and play, whilst CSP is still an engineering construction project, and if at 850'C, one needing very specialized staff.

The basic idea of CSP is good, so one hopes they can compete.

Huge advantage to any heat engine on solar- can run 24/7, rain or shine, using any combustion heat source.

No reason a good solar stirling can't be just as close to plug and play as PV. The engine has the same life and lower cost/watt. The mount and tracker etc is no big deal.

So where is my reference? Look at the NASA space solar engines. Look at the mission life. Look at how they are made, materials, part count, commodity costs, etc etc. Any reason they can't be cheap? No. So why are they so expensive for NASA? We all know the answer to that one.

"Any reason they can't be cheap? "

Yes. The hot end has to be a pretty fancy alloy due to both the temperature and the lack of lubrication. The reason the world is not running on Stirlings is not due to an oil company plot.

There ain't no "lack of lubrication"--here ain't no lubrication. Not there. That's why NASA will bet on them for 15 yrs in space.

The hot end can be 304 stainless and still give good efficiency. 304 costs more than carbon steel, but what doesn't.

The reason the world is not running on stirlings is because briggs & stratton is cheaper.

Well. Whats its name, (the Albuquerque based company that was building and hyping dishes with stirling engines), just declared bankruptcy. The cost per watt wasn't competitive with PV. I never thought the idea any good, their collectors looked like radio telescopes, and I couldn't imagine thm getting the cost per watt low enough. Not really a bad idea. If we were given a world without PV or fossil fuels, we would probably be building fields of these things. But, the more economical solution wins out.

That was SES. I argued against that old auto stirling as an obvious dinosaur with known genetic diseases but the money guys weren't listening. So there, goodby and good riddance. Too bad that such a dumb option would mess up the support of the legit players.

Huge advantage to any heat engine on solar- can run 24/7, rain or shine, using any combustion heat source.

Yes, the system can share a lot of plant with conventional thermal.
That gives one of the important 'big picture' edges over Solar PV.

No reason a good solar stirling can't be just as close to plug and play as PV.

You have just given one, indirectly. Because CSP usually shares thermal paths, that excludes plug and play expansion.
You need matched engineering plant, which is complex in drawings, approvals, and construction. - and certainly NOT easy to 'whack on a few more panels'

The engine has the same life and lower cost/watt.

If that were really true, CSP would dominate solar ?

The mount and tracker etc is no big deal.

Technically, no, but they are mandatory on CSP, and optional on PV.
The Mount and tracker excludes some uses, which gives the PV guys a breadth advantage.
Note also that the CSP heat flux has to pass thru the tracker, which has to give life-time maintenance issues... - again comes back to specially skilled staff.

Well, just wait a while and we shall see about that.

I love my new PV panels, and have a great time putting them together in various permutations and combinations. Sure enough wonderful!, esp in dim sunlight of the kind we get around here.

But if you happen to be in a desert and want mega-giga watts, I would bet on solar thermal. personally, I do not live in a desert and don't want to.

I live in a place where, with the kind of scrimpy energy diet I have, PV is lovely. Even more so when I have that little biomass stirling sitting in the workshop which on cloudy weeks cranks out a kilowatt of nice sinusoidal 120VAC on wood chips which the power companies dump in our field as they clear the power lines.

In a super-wasteful society, its easy to live on throwaways. I recommend it highly. You can take the resulting holier-than-thou to the farmer's market and sell it along with the rutabagas.

In my opinion cost per kilowatt hour or whatever is somewhat more interesting than efficiency. You have to pay for it, after all.

An alternative option is concentrating solar, which for me at the moment is good for hot water. I live in New England. The hot water system is powered by a loop from an oil-burning furnace that also drives the hot-water radiators, so the furnace is active in Summer to heat the water (closed loop from furnace to separate tank).

I save something like 150 gallons of year of oil through having solar collecting panels on the roof to heat my hot water. The units cost at the time \$9000, not counting the tax break that dropped the price to about \$5500, and depending on the price of oil (it wanders) are saving me \$300-\$600 a year.

I investigated solar collection for driving the hot water heat, but hot water in hot water heat is very hot, 180F or so, and the system generally does not deliver above 140 (the control panel reads the temperature of the outside closed loop that drives the booster tank in front of the hot water tank) in deep winter. Also, snow can be an issue; my roof has a shallow slope.

However, a solar concentrator that heats a pile of brick for 24-hour storage, heat being drawn off from the brick at 90 F. or so, quite warm so that I do not have to shove too much air around, might be a money saver also to heat the home. Many American homes in this area have central air conditioning, so you could use the same ducts. High release of hot air is a bit less efficient,but you can use current ducting.

In my opinion cost per kilowatt hour or whatever is somewhat more interesting than efficiency. You have to pay for it, after all.

Yes, you are right. Most people on TOD probably get this. What Tom is addressing is the fact that many people elsewhere don't get it. Here's an example.

EDIT: I just read further below, to SW's post, and realized that there are people here on TOD who don't get it either.

PV should be used for assisting passive means of heating/cooling ... fans etc. and pumping water, and small electronic loads

http://farm7.static.flickr.com/6072/6084184900_9a61fb5dea_b.jpg

Greenish as usual beat me to the punch but I have a bit of "Old Farmer" perspective to add.

The cost of new equipment, of any sort, is likely to go thru the roof in coming years-and this includes solar panels, and the associated equipment needed to use them.The cost in current day dollars per watt will fall, but not far enough, or fast enough, to offset the long term inflation that is utterly inevitable, given political reality.

This has everything to do with govt policy, and only a little to do with deflation, which can destroy housing prices, and drive down commodity prices, sometimes by a factor of four or five or possibly even more.But with only a few major exceptions, oil being one of them, consumer prices are not that tightly tied to producer prices.

Oil may be about two thirty or forty per gallon, very roughly wholesale, unrefined, and only a little over three dollars to four or five in finished form, processed, delivered and taxed.So a forty dollar a barrel move up or down can move comsumer prices a long long way up or down.

But just the FREIGHT on western coal is apparently around eighty percent of the price at a Georgia power station-electric rates wouldn't go down much if the coal were to be FREE at the mine, nor up much if the mine gate price were to rise say twenty five percent.

Bread has only a few cents worth of wheat in a three dollar loaf.

Inflation is a deliberate long term policy of the federal govt, and it will continue to occur, in everyday terms, excepting maybe stocks and real estate, and that sort of stuff , priced on perceptions , rather than the day to day costs of doing business, which must be and WILL BE passed along in real time.Nobody buys a load of my apples, or hauls them to market for the buyer, based on the potential price of oranges next year, or twenty years down the road.

In every day common sense terms, Alan and Greenish have scored bulls eyes in their comments about long term utility and wasted energy.A very large part of the energy we are using today is being piddled away in utterly frivolous ways, such as driving oversized cars to nowhere and keeping advertising lights on.

If part of that energy were to be redirected -which is essentially what Greenish is advocating-into renewables,the eroei would as a practical matter be of no concern whatever-it's better to drink a pint out of a gallon of milk that is surely going to get spilled than to spill the whole gallon.

And as a matter of every day economics, anybody who can buy a system now will probably be glad he did later, even though prices may fall for a while yet-they are sure to bottom out and start up again-remember the few cents worth of wheat in that three dollar loaf, and reflect on the fact that a lot of us can remember a president saying bread would never be a dollar in America.

My old tractor, which is forty years old, still works just fine, and a new one with similar capabilities would cost me over thirty thousand dollars.I don't remember where the stock market was then, but I could probably have just drove the tractor in the barn, and done about as well as I would have in stocks.

Carpenters and electricians purchasing power may fall, probably will fall, in the future, but their nominal wages will rise-politics , in the end, make that a certainty.

A solar system bought and installed properly now will probably look as good as an investment twenty years from now as anything else, and far better than most things.

Minor addition, in Pennsylvania and other states I have lived in, electricity that I buy is subject to sales tax, at this moment that is 6%. Electricity that I generate on my 6.6kw system is not taxed. I am rather
pessimistic concerning taxes, i believe that they will grow, not decrease.

Efficiency is not the bottleneck. It’s usually price.

I'd agree that price (\$/watt) matters more than Efficiency, especially on PV farms, but you do need to be careful of the tyranny of averages.
You cannot ignore Efficiency.

Sure, the average home usage might be 30 kWh, but that could have a seasonal component of 2:1, and the average daily factor might be 5/24, but that can fall to a fraction of that for a number of days.

Suddenly, by focusing only on averages, you have pushed up your storage costs, without even realizing it.

Apply two factors of 2, and only half a roof, and your 1/6, is too light.

-and that's just domestic roofing.

For commercial usage, roof area is finite, and Efficiency means more dollars.

That is what ultimately dealt to Solyndra - it was too easy to offer a customer MORE kWh of income, for the same price.
Who will they choose ?

A couple of comments from the sidelines at 3 am.

I very much appreciate Tom Murphy's good work in Do The Math. Always comforting to find stuff that does not make me feel like I am living in a Madhouse.

I don’t get this endless chatter here on economics and payback and all that when a huge fraction of what we are doing is burning up the world for mostly really stupid frivolity that does no good to anybody, and does not count the cost of burning up the world.

Proof. Just look at what’s being offered in the big box stores and car places. We could get along just fine with 1/10, or maybe 1/20 of what we do. lots of people do it.

If we don’t count the full cost then what’s the point of arguing about cost? Or is it that we have totally discounted the future? If it’s ok to discount the future, then what should I , a person who can measure his own future with half a meter stick- care about anything at all?

As for simple facts about PV. I bought a pallet of those Sun laminates for \$1050, rated at 1400 watts peak. I could have taken that same money and bought a trip to the west coast to see our grandkids.

We both agreed that the grandkids would be better off if we bought the PV instead. They give us fun things to do, and the kids can inherit them.

I am arranging work parties among the local treehugger types who want to learn how to DIY. Some of them already know, so this also gives me free labor and experience so as to avoid the normal stupid goofs from DIY. This also gives me some contact with the world I otherwise almost totally lack.

Besides, the people who seem to assume from the beginning that nobody does anything but totally selfish stuff are wrong on the face of it. Most of the geezers I talk with think just as I do.--Our purpose is to leave the world a better place than it was when we came into it- NOT to get a big fat car to show off in front of our house.

And-you don’t have to say it- we know we are very very far from having achieved that purpose.

I don’t get this endless chatter here on economics and payback

That's because you haven't swallowed the Blue Pill

You need to get with our mass-delusion religion and learn about why some people merit high deserving-hood in our society and others deserve a much lower or no deserving-hood at all.

More specifically, according to our religion, we operate as a "meritocracy".

That means that if you are born filthy rich and never work a day in your life, you merit high "deserving-hood".

That means that if you are born with the wrong skin color/ethnicity and work your butt off (in manual labor) you have low "deserving-hood".
That means that if you learn how to manipulate pieces of paper known as "financial instruments" which at the end of the day do not contribute anything physically real to society's well being but instead fool people into believing there is "value" in the papers, you have high "deserving-hood".

Got it? Get it? Good.

Not sure how it is in Germany and other countries, but the result of staggeringly high PV subsidies here in the UK is steep pitched roofs with PV modules fitted on both sides. Idiotic.

We have seen the biomass industry take a massive PR hammering about carbon emissions from the supply chain. Eventually people will start to realise that even a reasonablly well installed PV module actually has similar "external" emissions per KWh to an internationally supplied coal to biomass conversion (the ones which are taking all the flack), but when PV is oversubsidised as it often is, the poorly installed modules (on the wrong side of the roof) give a very poor payback to the emissions that were created in manufacturing and distribution, and not only that but almost all of those emissions were incurred up-front (unlike biomass which is incurred throughout the life - problem: no time value of carbon).

here in the UK is steep pitched roofs with PV modules fitted on both sides. Idiotic.

Well, if that is north/south I'd agree with you. If it is east/west it may be a good idea.

NAOM

That's exactly why performance based FIT's work. Pay ONLY for kWh at Reasonable rates from the capital rate base used to build new plant capacity. If UR Silly enough to Aim PV North, it's your money, Not OPM "Other Peoples Money". Using taxpayer money for installed PV nameplate is unbelievably stupid, corrupt and should be history.

Continuous updates on Feed-In's : www.wind-works.org - Find out if Bulgaria has energy policy to be proud of.

"That's exactly why performance based FIT's work. Pay ONLY for kWh at Reasonable rates from the capital rate base used to build new plant capacity. If UR Silly enough to Aim PV North, it's your money, Not OPM "Other Peoples Money"."

I agree to some extent, but the problem is we compensate by simply increasing the feed-in tariff so that people can do stupid things and still make money. And of course there is no mechanism to account for the destruction of EROEI and increased emissions per KWh.

In the UK the whole thing reached farcical proportions. The feed-in-tariffs were set to basically allow anybody to make a return by installing a PV module on roughly the right side of an average roof, but not really optimised in terms of orientation. Of course what that meant was if you set up your modules correctly and optimised the orientation, and made inverter savings etc with a large ground based array - you were making money hand over fist. But that was a disaster for our government, who had no intention of actually incentivising efficient well optimised PV arrays, and every intention of buying one vote per green-bling household. Therefore they rushed through a change to the legislation limiting the size of the arrays, so that in practise only small, mostly roof mounted, arrays would go ahead.

It actually gets worse than that, they even made a mess of the change so that now many of the large ground based arrays would install a single module by a certain date this summer, buying them a window of extra time to install the rest and get the big subsidies. So on top of all the other inefficiencies, the government has now effectively legislated a wasteful two stage construction process. You couldn't make it up, and they are now trying to change the change.

The whole thing is a steaming heap of moral corruption and waste which is fast destroying public credibility and draining the entire UK renewables industry of its last vestige of confidence in ever obtaining a meaningful and positive regulatory regime.

"If it is east/west it may be a good idea."

Oh. My. God.

That is even worse! Then both sides are equally wasteful. What a terrible system we have when people are fitting expensive and high energy cost PV to east or west oriented roofs. All consumers are paying for this nonsence now, one day the entire planet will pay if we don't wise up.

Look at an irradiation diagram. 35% tilt on an east/west still yields 90% of potential (ideal) power. At UK lattitudes. But utilizing both sides of the roof doubles the potential area. It's not as bad as you make it sound.. Partial shading of a section of a string during the year is possibly worse and happens a lot unfortunately.

Styno, I don't have the figures to argue, gut feel says that can't be right, but I know from long and bitter experience that gut feel can be a poor guide (I am on the wrong end of dumb assumptions about biomass all the time). Can you provide a link or show your working?

Having said that, even if we accept 90%, it is a 10% loss in revenue, 10% loss in EROI and 10% increase in GHG emissions per KWh. That is only conceivable because of over-subsidisation. Such lack of optimisation would never be acceptable in conventional generation, and it goes heavily against my personal ethos although I accept there are plenty in the biomass industry who wouldn't care and simply squeeze the poor consumer/tax payer for a little more juice.

"Styno, I don't have the figures to argue, gut feel says that can't be right, but I know from long and bitter experience that gut feel can be a poor guide (I am on the wrong end of dumb assumptions about biomass all the time). Can you provide a link or show your working?"

Here you go. Irradiation diagram from the Netherlands. Should be pretty accurate for e.g. UK, Belgium and Germany too I guess:

Here's a real life example for east/west installation from the excellent sonnertrag database (but there are many more, just use the search):

"Having said that, even if we accept 90%, it is a 10% loss in revenue"
Agreed at the absolute level, but in a real world I see it differently.
Knowing that the panels will pay themselves back twice or perhaps triple, I'll still earn.

"10% loss in EROI"
Again, true. But I argue that 90% of an sustainable EROI is still much better then any non-sustainable fossil fuel usage EROI.

"and 10% increase in GHG emissions per KWh."
Wrong. Simply put: every 1 kWh produced by PV eliminates 1 kWh of fossil fuel, after payback. Indeed, best places solar eliminates more, but the suboptimal PV setup still positively replaces ff use and therefore reduces GHG emissions compared to no PV setup at all.

"That is only conceivable because of over-subsidisation."
Perhaps, but not necessarily. If electricity price is high enough, subsidies aren't necessary (grid-parity), so if solar panels are produced cheaply enough even suboptimal placement can be economically sound over no placement at all. In such situations even an east-west roof system is better then no roof system when the roof orientation is a given.

"Such lack of optimisation would never be acceptable in conventional generation"
Ofcourse suboptimal generation happens with conventional generation as well. Think about a thermal electricity plant that has to use higher temperature cooling water in summer. Think about a newly built coal plant along a river in moderate climate and then think about climate change and what it will do to the temperature of that river water. People make suboptimal economic decisions all the time.

"and it goes heavily against my personal ethos although I accept there are plenty in the biomass industry who wouldn't care and simply squeeze the poor consumer/tax payer for a little more juice."
You aren't an entrepreneur if you don't attempt to squeeze the market for every little bit of juice. Unfortunately the energy market is not a level playing field. Subsidies are necessary to give new technologies a chance against established monopolies. In the end we should end up better then without subsidies (ideally speaking ofcourse), that is what the EEG/FIT subsidy is all about.

I can recommend Hermann Scheer' book "energy autonomy". He was the driving force behind the implementation of the successful German EEG, implemented somewhere in the '90s, and he describes clearly how the EEG/FIT system is designed to give initially expensive new technologies a fighting chance against the established monopolies (who also receive plenty of government incentives) by helping them to create a new industry (e.g. the PV industry) and force them to be able to function efficiently and competitively after a few decades using continuous FIT regressions over that time.

Hi Styno, thanks for the diagram, very useful, I will bookmark.

"Subsidies are necessary to give new technologies a chance against established monopolies."

I agree with you on that, subsidies that enable technologies that have the long term potential to eventually compete with or improve on existing technology are valid and have a long term value to society.

Also, just so you understand me, I am not at all anti-PV. My masters degree was largely PV focused (my thesis was on back contact effects on Cd-Te), and I would have likely had a career in PV if I hadn't graduated at a time in the mid 90s when the industry was going nowhere fast and there were no jobs. I agree with PV subsidies.

My beef is with sub-optimisation driven by laziness, ignorance, greed and political connivance. When new technologies are being developed and proven under the support of subsidies it is incumbent on all players to optimise and strive for the best possible results. With PV I don't accept that roof mounted arrays at only 80% of potential (for surely that is the output from your diagram for east orientation at 30 degs?) are acceptable under this criteria when larger, more cost effective and properly optimised arrays can do a far better job. There is no shortage of waste land for this.

I also don't agree that conventional generation would accept a 10% loss of potential (let alone 20%). That equates to 4% net conversion efficiency for a modern coal plant or 5-6% for a gas CCGT. I have a good friend who has dedicated his career to achieving 0.2% conversion efficiency and research is millions of dollars. OK, different sites have different cooling potential, but not to that extent, and appropriate sites are very limited (unlike PV). Since they are not directly subsidised, such commercial suicide would be very uncommon.

I read your diagram as 80% for 30degrees east or west. Not bad, but not the quoted 90% figure either.

The ninety percent figure sounds high to me. But maybe UK is cloudy all winter, and only the summer season matters? In any case, with the purported E and W facing system, you have one source of cost saving/optimization, size your inverter for just one side operating at a time. That might save you 10% of the cost.

It's not wasteful in summer up north. Sunrise is well north of east, sunset is well north of west. A due-south roof misses several hours at both ends of the day.

In winter east-west won't get you much, but with only 8 hours of daylight anyway, and the heavy overcast, there isn't much to lose in any case.

In the Midwest there was a house style that was basically a square with a roof-section over each wall. Four triangles with a pretty good slope that met at a common peak. So you would have a roof section facing each of the cardinal directions. Three of the four sides would seem to have solar potential.

A lot of those houses also had two porches, with separate shed style roofs. There was the "company" porch facing the road, and the "working" porch where you could take off the barn boots and such. If one of those faced south they would be fair game too.

That was a practical house design, One bedroom down, three or four up, usually a basement as well. Easy to heat even in Wisconsin. Only looked good in white though. Otherwise it loomed up too much. Why can a barn look good in dark red and not a two-story house?

...is steep pitched roofs with PV modules fitted on both sides.

Why not make a nice carport, or front/rear porch, where you can have a nearly flat top with correctly angled PV, or a correctly angled ( carport | porch) top and PV parallel to its roof?

I would prefer that to altering a home's roof, and potentially causing leaks for rain and such to get in.

Rembrandt - Great thread...mucho thanks. Not sure if it's still valid but decades ago I saw a map depicting the financial value of solar. The best spot wasn't in AZ or FL. It was Montana. They obviously get a lot less sun shine then many spots in the country. But the map depicted "value"...not efficiency or absolute output. Though the PV output might be relatively low, the financial gain was tremendous given their needs and expense to supply those requirements. Those incremental BTU's were small but worth a great deal especially during their brutal winters.

I can sympathize with your feelings. I'm a career development/production geologist unlike exploration geologists like westexas. When he hits it tends to be very big and thus very "efficient". When I hit it's usually small , relatively unimpressive and not very "efficient"...low volume for the effort. But typically much more profitable and might happen 10 to 20 times as often as an exploration geologist make a big hit. Cumulatively I've probably developed as much or more reserves as the average exploration geologist (but probably not a much as wt since he is above average). Just like your low (and lowly) inefficient PV system we don't get the big headlines. We're just proud mud grunts in the battle against PO. LOL.

I disagree. This is not to say that as a consumer one should wait for a more efficient technology. But efficiency is the path to lower cost. In all the different technology groups. This is because any increase in efficiency translates into more power output for the same balance of systems costs. All the support structure. The metal. The glass, the module itself. These are fixed costs independent of the semiconductor. It is very difficult to find reductions in these arial costs. When you increase the efficiency of your technology you leverage the investment in all these other ingredients. This also includes the site although that is of less concern to the residential user.

Additionally, look at the map of solar insolation. What jumps out at you? It is non-uniform isn't it? In some places we have a huge direct resource like the desert southwest. Other places not so much. PV conversion technology should be looked at as a tool to convert this resource to electricity. We are fortunate that we don't just have one tool for such a diverse resource. The tool that makes sense in an area high direct normal insolation in the desert southwest, where we might exploit the resource on an industrial scale is not the same tool that makes sense in the midwest or the mid-Atlantic region on residential homes.

Big dumb institutions like corporations and governments want a single solution. A magic bullet. But PV is going to come in many different forms for many different specialized applications to take advantage of a very different resource in different settings.

I'm not sure what you are disagreeing with.

The OP doesn't claim that we should stop seeking improved efficiencies, just that we need to understand that even current PV at 10%-20% isn't somehow pathetic. It's merely a 'conversion efficiency', not an overall effectiveness number, which I think gives people the false impression that, as with our grades back in school, would be seriously Failing until you get up into the 70's or something.

In his conclusion, Rembrandt was a bit anguished over the question of 'Area Required', but as PV is a somewhat lower density energy source than Wind and Hydro, to name only two, I wonder what that required area would become with a reasonable mix of those, Solar Heating, and of course a full-quiver of Negawatts Programs to eliminate wasted and luxury watts.

You would be surprised by how many of those controlling the purse stings at funding agencies buy into the argument that 'chasing efficiency' is a waste of time. When clearly improving performance at the cell level is the surest rout to lowering over-all cost since it leverages all of the other fixed costs. Any analysis that labels those concerned with efficiency "efficiency snobs' really doesn't do us any favors in the surprisingly difficult battle to convince these folks that the effort to develop these technologies to their full potential is worth the effort.

SW - If I understand Rembrant's point correctly: If PV A is 30% more efficient than PV B but PV B produces the same amount of electricity at 30% of the cost on PV A than buying PV A is being a snob: having bragging rights about being more efficient but producing at a higher costs. I could care less how inefficient my PV system is if it cost me less to produce the same amount of electricity. Show me a more efficient system that will produce the same power at the same price or less then we have something to talk about. Until then you would just be wasting your time and mine.

PV A does have a use even if it's electricity is slightly higher priced the PV B just because many houses don't have enough roof area for a less efficient PV system to cover the owners` needs. This is exactly why I bought expensive but also very efficient Sunpower panels. The slightly higher price for a kWh of electricity is still cheaper then a kWh from the grid though.

In hindsight I would have bought Sanyo HIT panels because they are less picky about the inverter technology (Sunpower panels -due to the way their cells are wired- needs a positive earth connection which requires an inverter with galvanic isolation. Sanyo's don't care). But I thought the Sunpower panels were more sexy.

(Sunpower panels -due to the way their cells are wired- needs a positive earth connection which requires an inverter with galvanic isolation.)

I think pretty much any reputable inverter with an isolation transformer would do fine with Sunpower. Unless you wanted to use a transformerless inverter (which would surprise me, because they're pretty newfangled and hardly anyone's installing them yet) I'm not sure why you were concerned about this. I hope nobody talked you into buying a more expensive inverter that you didn't really need.

Sunpower has at times been really cranky about using their panels with equipment that doesn't have their name on it. It's pretty much a crock of nonsense since they just take other companies inverters, set the default grounding to positive, and replace the labels.

I want to correct an erroneous statement that PV is a lower power density source than wind. On the face of it, solar power densities (averaged over day/night/season) top out around 300 W/m², while wind can get to >500 W/m², and PV only converts at 15%, while excellent turbines can reap 40% of the available power. So it looks like wind wins by a factor of six (but not necessarily on the same patch of land).

But we need to consider another fact. The wind density number is for rotor area, not land area. The rule of thumb is that windmills need to be spaced 5 rotor diameters apart side-by-side, and 10 rotor diameters apart in the direction of the wind. Otherwise, one robs the other and the wind is choked over your wind field. If you do the math, the areal coverage in this scheme is 1.6%. Now the best wind site generates only 10% as much power as the PV farm per hectare of land.

Now the best wind site generates only 10% as much power as the PV farm per hectare of land.

At first glance it looks like WTs don't occupy much land, i.e. what percentage of a windfarm is occupied by road, and pads? But, because of security concerns, (theft and liability), the whole area is usually off limits to the general public. I think similar concerns will apply to rural PV farms, but at least here the MW per acre placed off limits is much larger.

eos - I suppose it gets down to site specific details. The pics i've seen of our west Texas WT's shows grasslands with cattle grazing right underneath the towers. In such circumstance the foot print seems irrelevant. Unless the PV panels were raised above the cattle they could be a problem. Likewise about 40 years ago I got a first hand look at the WT's in the Tehachapi (sp?) Pass in Ca above Bakersfield. That foot print was even less relevent: the land looked completely worthless unless you were into raising cactus and rattle snakes.. LOL

Rock. That was my point. Cattle grazing is not usually public access, i.e. other that WT maintanence workers and occasional visits by the ranchers, they are effectively off limits.
It certanly restricts land usage to low value activities.

Well who knows: I got close to many wind turbines in all Europe (no farmland though) without restriction, but was once chased by farmer when I crossed a meadow with cattle on it (no windfarm though). So wind farms are probably off limits when they are on farmland.

Regardless: What high value activities did you have in mind in the windy regions where nobody lives and just some cattle might graze?

In many areas, they are on the hills. Would be great for natural areas, parks and whatnot. Maybe the Europeans are less litigious. In the USA if a member of the public was killed by an errant WT blade (once in a while they fail and go flying), the ambulance chasers would pounce. Similarly if the member of the public was electrocuted trying to steal copper wiring from the WTs.

was once chased by farmer when I crossed a meadow with cattle on it

I don't blame him at all, a lot of people get killed doing what you were doing. You'd appreciate it, too, if there was a bull you hadn't seen.

NAOM

Besides that I basically grew up on farm and brought the cows home in-numerous times: He wasn't chasing me because he was concerned about me, but because he didn't like the fact that somebody dared to trespass his farmland or maybe he just thought I was after his cherries.

Huh, cherry picking again ;) I too am used to farms but too many city folks just think of cows as cuddly - mistake. I knew someone who cleared, by a margin, a five bar gate when he discovered the field was L shaped and the bull was around the corner.

To be more on topic I note your comment, further down, about the benefit to the economy with people building installations to carry PV financed by FITS. Why on earth do American politicians see PV as being bad for jobs? What is so difficult in a push for renewables that would boost jobs?

NAOM

The frame-conditions in all sectors including the energy sector are set by the politicians/corporations which are currently in power and not by what would be most sensible to a country's economy, job-market, security etc. as whole.

And renewables including PV have little say and compete against FF-sources which obviously have more political power and on top of that renewables take their valuable market-share.
http://www.dblinvestors.com/documents/DBL_energy_subsidies_paper.pdf

...the federal commitment to Oil&Gas was five times greater than the federal commitment to renewables during the first 15 years of each subsidies’ life, and it was more than 10 times greater for nuclear.

"west Texas WT's shows grasslands with cattle grazing right underneath the towers. In such circumstance the foot print seems irrelevant. Unless the PV panels were raised above the cattle they could be a problem."

And why not give the poor little doggies a bit of shade from that blasted WTX sun with some well place, elevated PV? It might keep them from going loco and voting for Mr. Goodhair types '-)

Unless the PV panels were raised above the cattle they could be a problem.

The solar panels would most certainly shade the grazing area more than the wind turbines so the same shaded acreage would produce less fodder. Raising the solar panels raises the cost of the installation as well. So likely solar sites will be single use whereas wind sites often support agricultural use as well.

Lots of good solar sites where the grazing is marginal though so its not a killer issue.

The solar panels would most certainly shade the grazing area more than the wind turbines so the same shaded acreage would produce less fodder.

Not necessarily. Not even usually. Environments where sunlight is the limiting input for plant growth are rare. Usually it's water and / or soil nutrients.

West Texas ranch land has too much sun, too little water. Using elevated PV panels to provide a 50% shading of the land below would reduce evaporation and increase growth of forage for cattle.

There's even a cheap way to do it that leaves the land open, aside from a support pole every 100 feet or so. It's a "tensegrity" net that creates a tent-like roof over an area, with solar panels pre-installed at nodes in the netting.

The CoolEarthSolar (haven't checked up on them recently) folks concept, was to string their collectors from cables, mounted off of telephone poles. The idea was the land underneath could be used for farming/grazing. If the critical resource for your agricultural land, is not sunshine, but water (very likely for west Texas) the extra shade probably won't have much effect on productivity -it might even help it. In any case, the value of the electricity is at least ten times the value of the fodder.

Looked at a couple of the CoolEarthSolar web sites but they dish up a pretty thin soup. A 1.5 MW Pilot plant was to be online in 2009 in Tracy CA--couldn't find any more on that. The most recent press releases are about a year old mentioning their doubling the office/manufacturing space at Livermore. They are the outfit talking up tensegrity

A Support System Holds It All in Place…
The concentrators are suspended with our patented support system based on the architectural principles of tensegrity. (Tensegrity structures stabilize their shapes by continuous tension or "tensional integrity" rather than by continuous compression.) The resulting system of wood posts and steel cables uses a minimum amount of material, has a small footprint, and causes the least disruption to the natural environment of any solar power plant.

Thanks for the correction, Tom.

So, to the larger point, do you have a picture of what kind of area might be more reasonably demanded for PV once we balanced it into a blend of the usual suspects, including an adjusted demand profile?

Bob

Concerning the power density of PV arrays, did you include the land area used by them? PV panels must be spaced apart to prevent shading. The amount of land occupied by dual axis tracking systems depends on the latitude of the array. The highest land use density is at the equator and the lowest is at the poles. Single axis tracking systems have higher land use density than dual axis ones. IF PV panels are mounted on an inclined residential roof, the shady side of the house would not be a suitable location for PV panels. For the latitudes of the U.S. the PV panels in single axis tracking systems occupy about 1/3 of the land and dual axis ones occupy about 1/9 with some shading in the morning and evening.

The map with the black dots showing the land area needed to produce 18 TWe appears to assume sunlight normally incident on the PV panal (1000 W/m2 * 6 hr / 24 hr / day = 250 W/m2/day for Arizona, no clouds). It appears to be showing the surface area of the PV panels, not the required land area which could be 3 to 9 times larger depending on the type of array. If the PV arrays are overbuilt to compensate for cloudy days, then multiply the land area by 4. I think the dots should be 12 to 36 times larger.

But efficiency is the path to lower cost.

Sorry, but no, it isn't. Right now the cheapest solar panels per watt, First Solar's CdTe, are the least efficient. Sunpower's highest-efficiency-on-the-market panels are more slightly more expensive than average.

There is some small savings in balance of system components if you don't need to support as many panels, but that is rarely significant enough to reduce overall costs. Mostly you go for higher efficiency panels only if you really don't have enough space, or if the space costs you money (e.g., land for a solar farm, rather than a roof you already have).

When you are producing energy, you pay for efficiency.

I have some question about the efficiency of the photosynthesis:

Is the 1-4% efficiency of the photosynthesis counted on the area of a leaf or one plant? Or for the total amount of solar energy stored as chemical energy in a given area of forest?

And with forest I mean the whole biological system (trees, bushes undergrowth, fruits animals).

Otherwise the comparison between photosynthesis and PV is not comparing apples to apples.

Wood is still the cheapest mean of heating in Sweden.

/Milos

Milos, as far as I know it's incident light per hectare (or acre if you prefer).

The 1 to 4 percent is the harvested biomass. Usually the roots are not harvested - unless they are the edible part. 4% can be achieved under "laboratory conditions". Normal in-the-field efficiency taken over a whole growing season would be closer to the low end.

For PV installations, we could expect about 50% of the area to be used for inter-cell spacing, panel bezels, access-ways, and balance-of-system structures. So 15% efficient cells give about 7.5% overall efficiency.

For crops the access-way and balance-of-system area is smaller, so the overall efficiency is still over 1% for maize.

The most efficient crops are annuals planted as a monoculture. Forests tend to start out at 0.5% to 1% efficient when young, and go downhill from there. But the ability to store energy as wood and use it in the winter is vital in Sweden. ;-)

For PV installations, we could expect about 50% of the area to be used for inter-cell spacing, panel bezels, access-ways, and balance-of-system structures. So 15% efficient cells give about 7.5% overall efficiency.

If it is a non tropical installation, the panels would be tilted -or perhaps tracked. So the efficiency would be higher than 50% of the panel efficiency. I.E. at low sun angles, most of the sunlight would hit a panel, whereas at noon, at lot would get through.

So then you are not measuring the true efficiency of the photosynthesis but what we think is efficient out our point of view.

I think we humans have a tendency of underestimating the efficiency of ecosystems by neglecting al of the services it does for free, as binding soil with the not edible roots for example.

The OLR (Outgoing Longwave Radiation), that is the energy leaving earth as infrared radiation, from a rainforest is on the same level as the winter areas in the northern hemisphere. If you have ever walked from direct sunlight in to a rainforest you can feel how much colder it is in a rainforest.

I am pretty sure a natural forest binds more energy than a manmade monoculture forest. Maybe we think much of it is not useful but that is another story.

What I am saying is you can not take a plant out of it’s ecosystem and in to a laboratory and measure it’s efficiency. Because it’s part of a system and you should measure the system as a whole.

So to make a good comparison I would ask how much OLR does a solarpanel reflects compared to a rainforest?

Here is a link on the subject from Folke Günther:
http://www.holon.se/folke/kurs/Ecologicaldevelopment/Termodyn_en.shtml

Milos

So to make a good comparison I would ask how much OLR does a solarpanel reflects compared to a rainforest?

You raise some interesting points, but I'm not sure this is entirely apples to apples either. The energy from the solar panels is used elsewhere from the array, rather than at the array location. It may end up embedded into all kinds of things that might raise - or conceivably lower - OLR elsewhere. Unlike the forest, the ecosystem of the solar panel isn't confined to the location of the solar panel.

Another thing to think about is comparing the OLR of a solar array to the OLR of, say, the composition shingle roof it might be covering up.

Im not at al an expert in the area of messuring how effienct a certain application harnest the suns energy. But to me it sounds strange that the photosynthecys is that inneficent and i think it is because you measure it taken out of its system. Like in a lab or a field of crops grown in a monoculture. That would offcourse apply to meassuring a PV system to.

Offcourse i think PV is better then a plain roof or dessert.

Pardon my spelling, I don't have a spellchecker now and english spelling feels ilogical to me. =)

Have I ever mentioned that an easy solution is a voluntary reduction of energy demand? But this doesn’t sound like expansion/growth, so how would that idea ever gain traction?

By supporting growth of efficient devices.
My household is currently at 300 kWh electricity consumption per year and person (and no, we are not missing out on any comfort. Most people are simply unaware what efficient appliances/lights/TV/computer can do).

Maybe you’ll stop when you realize that it converts thermal energy from burning gasoline into locomotive power at an efficiency around 15–25% (and this on a finite resource).

Actually the best-selling American cars probably only reach about 5% efficiency in city driving.
The VW Golf VI with its small 1.2 liter efficient internal combustion engine only reaches 16% in city driving: http://www.empa.ch/plugin/template/empa/*/104369/---/l=1
Of course, if you were to calculate the actual effiency of transporting a single 80 kg person, the best-selling American cars would not even reach an efficiency of 0.1%.

And this statement:

This works out to 430 square feet, or about one sixth the typical American house’s roof (the roof area of a two-car garage). What’s the problem?

As reassuring as this picture is, the photovoltaic area represents more than all the paved area in the world.

Unless you are saying that PV also needs to substitute the tremendous primary energy lost in all the cooling towers and all the exhaust systems and assume that old fossil fuel furnaces would be replaced by resistance heaters and not heat pumps and PV (for whatever reason) also needs to replace already existing hydro-, wind-, geothermal-, biomass-power-plants and all wood furnaces.

Sorry to nitpick, but

And this statement:

This works out to 430 square feet, or about one sixth the typical American house’s roof (the roof area of a two-car garage). What’s the problem?

As reassuring as this picture is, the photovoltaic area represents more than all the paved area in the world.

There's no contradiction there. All it shows is that there are a lot of houses, and that 1/6 of that total roof space is more than the total paved area.

All it shows is that there are a lot of houses, and that 1/6 of that total roof space is more than the total paved area.

Well, I highly doubt this to be the case.

A quick Google gives some figures as a start...

Paved area of USA: 61,000 square miles (slightly bigger than Georgia).
Number of households: 112 million

Which would require an average house to have about 91,000 sq foot of roof space (unless my maths is way out).

So it looks like the "total paved area" comparison requires some clarification.

See my clarification below. The 1/6 roof area was only for domestic electricity—a small portion of the nation's energy demand— at 15% PV efficiency. The paved area was for total U.S. energy demand at 8% PV efficiency. Thanks for providing the paved area. A crude comparison of supporting 1/4 of the global 18 TW (U.S. share of energy is currently about 25%) at 8% indeed puts the PV area slightly larger than the paved figure you quote.

Ah, Yes, apologies for misrepresenting there.

In trying to provide some dis-ambiguity I succumbed to the common disease of "mixing my stats up".

Aside my fumbled interference, I'd like to thank you for a very interesting article (it even had me looking up the price of PV panels on ebay, although sadly still outside my current budget).

And that we are only talking about residential power and residential rooftops. If we want to power other sectors of the economy, much more sirface area is required.
But, his computations assumed 8% efficient collection. Maybe not so far off for PV farms, where because of shading issues, there are significant gaps between panels.

As I said below: Industrial, commercial and government buildings have lots of their own roof area. Small household roofs don't need to power Walmarts, airports and car factories

Great to be at < 1kWh/day/ppl in your house. I'm close to the same number, and agree that it does not hurt.

As for the contradiction, there is a large factor yet to consider. The 1/6 rooftop number is computed to supply the average American house with 30 kWh of electricity per day, which works out to a total power of 0.15 TW (30/24 kW × 115×106 households). This is only 5% of the total U.S. demand. So multiply the 1/6 roof area by 20 to get the area to support the U.S. 3 TW appetite. And throw in another factor of two because the roof case considered 15% efficiency and the whole-country solution used 8%.

Ultimately, the large factor just says that residential electricity is a small part of the total energy demand.

Ultimately, the large factor just says that residential electricity is a small part of the total energy demand.

Yes it does, but mostly because electricity demand is less than a fifth of the total energy demand.
(Besides industrial, commercial and government buildings have lots of their own roof area. Small household roofs don't need to power Walmarts, airports and car factories.)
Keep in mind: The US coal power production is actually only about 0.2 TW on average. It simply does not make sense to produce over 10 times more electricity with PV (on AVERAGE) than what coal power plants currently deliver.

PV may partially have to replace the electricity produced by fossil fuel power plants, but it won't need to replace 3/4 thirds of primary energy wasted due to inefficiencies in converting fossil fuels into useful work. An electrified economy would simply be much more efficient.

I know this article regards traditional solar cell techniques and explicitly excludes high-end cells (as not being economical).

But still I'd like to point out that solar cell development hasn't by far reached it's endpoints in terms of efficiency per \$. At this moment, Sunpower, US pride in darksunny days, delivers panel efficiency over 20% at commercial prices.

As for the future, PV efficiency looks even brighter: New nano techniques promise solar cells that are nearly 100% efficient with nanocrystals capturing not only longwave irradiation but also shortwave using a single photon to create multiple electron/hole pairs thus eliminating (by large) the photon's energy being lost as heat in 'rattling within the crystal structure'. If these nanocrystals can be massproduced economically then it would greatly increase efficiency while simultaneously reducing material and area use.

I think we need to consider the nanocrytal panels as a longshot. Great if they can in fact be made at a low enough cost (or at all), but don't hold your breath waiting for them. Definitely worth throwing some research dollars at, even if the odds of success aren't great.

There is also a very secretive startup Alta Devices (GE is an investor), that claims to be developing a kind of thinfilm panel, promising 30% efficiency at low prices. They claimed lab test cells @26%. I think it was guessed (by people looking at patents/personell) to be some sort os Gallium Arsenide tech.

Alta devices is an example that is contrary to the premise of this piece. These panels will be more expensive than any panel currently on the market. But they will also be more efficient than any panel on the market conceivably resulting in electricity that is as cheap or cheaper than the cheapest modules out there. With the added advantage of taking up less space on your rooftop. I am not at liberty to say just what these things are but the guesses are pretty warm. The point is that it isn't snobbish to pay for performance. People have always paid a premium for high performance. Of course you don't want to be stupid about it. But you could just as easily say that about the person who buys a sports car that can go 180 miles per hour when the speed limit is 75. Some people want things that perform well. Because there are usually other advantages. In the case of PV it means that for a given output it will require less roof space. Additionally, it is the crystalline device technology that is typically of higher performance vs polycrystalline and amorphous technologies. The reliability of the crystalline technologies is of greater certitude than that of the polycrystalline technologies. Grain boundaries are potential sources of degradation. Like most things in life, you get what you pay for ultimately. Paying a little bit more for a high quality single crystal technology like that from SunPower is worth the differential in price in my view.

These panels will be more expensive than any panel currently on the market. But they will also be more efficient than any panel on the market conceivably resulting in electricity that is as cheap or cheaper than the cheapest modules out there.

That is always the hope, but many companies compare what they have in their labs, with what others are shipping now, when they should really compare with with others will be shipping (ie is in their labs now )

or, if you are a commercial site who will sell rooftop power, you get more income
from a finite roof area.
Few are going to build bigger roof areas, just for the Solar PV

I see Alta Devices appearing here, with one number (Efficiency):
http://en.wikipedia.org/wiki/File:PVeff%28rev110901%29.jpg
- note that GaAs is not new, and was at 22% way back in 1975, so the important number will be the COST.
Alta are on the thin-film GaAs variant.

"Few are going to build bigger roof areas, just for the Solar PV"
Have you been to Germany lately? Many, many oversized roofs for PV there...

Some just even build roofs for PV-systems

They call them for instance Solarcarport or "Energiehalle" (energy-hall). (The FIT basically pays a farmer a hall for free and hall-builders create jobs and pay taxes).

Interesting to see panels in the full shadow. This is something that only very rich countries can afford, like Germany, where the country has a horrible performance (half the energy production than Spain in per MW installed power), but they still continue installing. Only a country with a huge resource surplus can afford this wasteful designs and additionally to show them with pride

Actually, the PV industry in Germany not only creates thousands of jobs and reduces the dependence on fossil fuel imports but pays more taxes than what it indirectly receives in feed in tariffs.
http://www.forium.de/redaktion/steuereinnahmen-der-solarindustrie-ist-ho...

Also, the feed-in tariffs for PV in Germany are meanwhile low enough that they only amount for 0.03 cents/kWh for each additional GW installed: http://www.solarserver.de/solar-magazin/nachrichten/aktuelles/2011/kw41/...

In my efficient household this would amount to only €0.0075 per person and month!
Taxes for military expenses are actually about 10000 times higher, despite the fact that I live in relatively safe central Europe! And the military DOES NOT pay taxes NOR does it reduce dependence on imported resources on the contrary.

Those are great points.

It's important to keep the imperfections in clear perspective with some of the simply massive waste that should be continually in the forefront of our minds.

Another thing to point out is that these Solar Panels are still completely modular, and can be refitted, sold and relocated at a later time when an owner wants to take better advantage of their potential.

I really don't buy into Greenish's 'Performance Art' and Stone Head comparisons in this case, though I appreciate his willingness to say that even he owns PV on his home. I disparage the prep school my parents taught at, and we 3 kids got a free ride through, and the critiques are, I think reasonable and valid. But I would trade it for anything either.. I could have done much worse.

We use Electricity in many frivolous and useless ways.. but that is hardly the extent of it, and I don't think PV or renewables will ever bring us to the levels of overconsumption and overpopulation that this Petro-party has done, even when PV is a clear result and beneficiary of FF in its creation.

I really don't buy into Greenish's 'Performance Art' and Stone Head comparisons in this case, though I appreciate his willingness to say that even he owns PV on his home.

My comments may seem slightly schizophrenic. If so, they're being read correctly.

There are two perspectives I personally toggle between: "near future" and "far future", where "near" worries about the people I know and feels empathy at the problems coming generations will face. In that mode, I put PV on the roof, live a low-energy life, and engage in things like intervening to shut down oil fires.

In "far future" mode, I'm more concerned with the trillion or so humans who COULD live good lives on this planet if we don't preclude it; and who are being erased in their probabilistic billions each year now, as well as dolphins and other evolved lineages which mean a lot to me and may be lost. In that mode, it's clear that the interests of humans and other species mostly coincide.

I sometimes post from the latter perspective because it's in the vast minority.

So in one mode I can be in favor of Alan's trains and PV and many other things which will cushion the crash, but I'm aware that these are probably at odds with the more-logical low-discount-rate long-term view, which is probably best served by a fast crash and a period of very bad times in the near future.

Others have been successful trying to reconcile these perspectives, but I keep them separate and try to be aware which mode I'm in. Ultimately, preserving the planet for hundreds of million of years in good shape with humans, dolphins, and other critters on it is to me better than a loss of humans and dolphins, and a reversion to jellyfish and cockroaches. I've arbitrarily decided that living awareness is a good thing. If so, anything other than the long-term view is hard to support.

I pretty much saw that you were allowing for portions of both views in there.

I tend to think that the butterfly effect leaves me generally unwilling to try expecting I can do much with a REALLY long-term view.. but I think the 7-Generation principle is a pretty reasonable standard. In the meantime, using electrical and electronic technology is at least far less immediately devastating than the many fires we keep lit these days, so I have allowed that form of tech to play the role of a stepping stone away from the worst of today's slash and burn.

I know there are examples of how that is even backwards.. it is still going to be essential to watch for the various consequences, and make adjustments.. but it's a start. Maybe.

I don't think I'll ever buy into the Whole-Hog Nihilism, so that's where it leaves me ATM.

I think you can tell, from this and past posts, that you and I don't differ all that much in our perspectives. And for what it's worth, my view is the opposite of nihilism; I don't think we've earned the right to it, the self-indulgence of deciding that we can't affect the future to lessen the harm done.

When speaking of complex/chaotic systems, the butterfly effect is a good perspective to keep in mind in terms of envisioning any specific outcomes at any specific future time; they're inherently unpredictable. However, to balance that there are aspects of those outcomes which are utterly sure. If the last hummingbird goes extinct in 2045, then all future systems will lack hummingbirds. Path dependence includes both sorts of aspects. One can alter the relative probability of classes of outcomes, and we do it every day. I can predict that the weather on venus ten years from now, to the day, will be about like the weather was today, and devoid of butterflies in the bargain.

If we don't take responsibility for the next hundred million years, who should? Rhetorical question, not that you'd disagree. But this is the mass extinction; and what we do over the fairly near future will determine what gets through the bottleneck to that hundred million years.

To the extent we can do that, we should try... and in some cases, we can try while getting our power from PV; why not?

Greenish,

Are you so pessimistic about the long-term because of climate change and species extinctions, or because of energy/resource limits?

Actually, I'm an optimist. Activists have to be. I've seen big changes accomplished against long odds before, so I think it's worth trying.

I seem like a pessimist to some because my conclusions about the seriousness/importance of the earth's predicament are more dire than theirs. I have a nearly zero discount rate when it comes to activism, which means assigning importance to the next million, ten million, and hundred million years as well as the coming hundred. Assigning value to that future as though it were real leads one to different conclusions about what's more important now.

Now the things I'm scared of are the mass extinction, the coming human bottleneck meltdown and resource-grab wars, the desertification of rainforests, the loss of large ocean species, ocean acidification, and the CO2 heat-forcing experiment which will make the mass extinction worse and lead to fewer and more desperate human lives in the future. That isn't pessimism, that's just paying attention. The near-certain drawdown of half the human population in the coming hundred years will probably not be a picnic either, though I'll be safely dead for most of that.

My optimism is in understanding that stuff, and knowing that at least in principle, it can be made better than it would otherwise be; and feeling that I need to attend to that as my #1 priority, as I have the last 4 decades.

Perhaps a bit much for a solar power post, but it was a fair question. I won't object if the moderator wishes to remove this.

best

I have a nearly zero discount rate when it comes to activism

That seems unrealistic. Think of it this way: what are some of the changes you would most like to see in the world?

An acceptance of climate change by the US and China?
A perfect battery - cheap, durable, etc?
A drop-in replacement for FF which emits no CO2?
A breed of cattle that emits no methane?
A perfect contraceptive?
A cheap and effective method to educate all of the 3rd world's girls?
A cheap and tasty replacement for deep-sea fish?
A cure for cancer?

Now...ask yourself: does it matter whether one or more of these things arrives tomorrow versus 100 years from now??

-----------------------------------------------------

the coming human bottleneck meltdown...near-certain drawdown of half the human population in the coming hundred years

Now, is this based on ecological concerns (climate change and species extinctions) or because of energy/resource limits?

About 55% of the coals energy is wasted while generating electricity, about 45% of gas' energy is wasted while generating electricity, 75% of the generated heat in a nuclear powerplant is wasted while generating electricity, many people like to drive very inefficient SUV's, sportscars or even Hummers (ever heard of cycling?), we build giant poorly insulated McMansions and occupy them with only ~2.5 persons, waste valuable drinking water keeping the lawn green in a desert. Some people even seem to heat their home using purely resistive heat, what a waste of perfectly good electrons! Etc. Etc. EROEI...sustainability...what?

We could be complaining about the massive enormous waste of primary energy we see every day around us, but here we are busy complaining about one person having put solar panels somewhere less ideal and getting money for the kWh's they produce. Is there a big picture somewhere?

Interesting to see panels in the full shadow.

I'm not sure which picture you think shows panels in full shadow. I see no shading in any of them.

Maybe your point is getting lost in translation.

Sure those are good points, I won't argue with them and I didn't want to say we should wait. On the contrary: for many people PV is already at grid parity. On top of all the other good reasons there's increasingly also the economically sound reason to install PV.

I do think that it's the continuous roll to roll produced thinfilm type that will become the real mass produced PV variant in a few years. The mono- and multicrystaline are just the initiators for the real boom.

It would be awesome if cheap roll to roll thinfilm could be merged with extremely high efficient nano sized crystals tech one day. They seem a perfect match to me. Efficient, cheap, automated continuous production, low material use. Just awesome.

I'll go have a nice dream now...

There is also a very secretive startup Alta Devices (GE is an investor), that claims to be developing a kind of thinfilm panel, promising 30% efficiency at low prices. They claimed lab test cells @26%. I think it was guessed (by people looking at patents/personell) to be some sort os Gallium Arsenide tech.

These 'coming soon!' types of news just seem, in my humble opinion, to make people put off trying to implement existing products.

Regular sliced silicon PV has been around to average people since, say, the 1970's? And a few TODers say such panels are commonly still working and producing power for them....

There's also another promising approach to higher efficiency PV that Tom (not Rembrandt -- pay attention, people) didn't mention. I believe it uses either fluorescent dyes or phosphors of some sort (quantum dots?). The material intercepts photons of short wavelength light, most of whose energy would be wasted if they were captured in the PV material, and emits longer wavelength light that can be converted more efficiently.

As the author notes, efficiency can matter if appropriate roof/land area is constrained but in my experience, it is cost that drives sales and efficiency follows. Going back about 5 years to the height of the silicon shortage a more efficient solar panel like the Sanyo 200 watt cost about 10% more than it's less power dense cousin the Sharp 208 watt panel. At a size of ~12.8 sq. ft and ~17.5 sq. ft. respectively the additional cost was viewed by many as a fair trade off and both panels sold well.

Today the cost of a more efficient panel has dropped by 50% but the cost of a less efficient panel has dropped by over 60%. This has driven sales toward less efficient solar panels. Which in turn has driven research and further efficiency. Sharp will release a 250 watt panel in the same 17.5 sq ft foot print in Q1. I use Sharp as an example, many other companies offer a similar 240-250 watt solar panel.

Two years ago only First Solar was able to produce solar panels for under \$1 a watt. By the end of next year every important manufacturer will be at or under \$1 a watt in production costs. Add 5-10 cents a watt for manufacturing in Europe or the US. This will continue to drive smaller and/or less efficient manufacturers out of the solar panel business.

I am surprised by the level of ignorance about what a subsidy is, when coming to talk on subsidies on energy systems.

Subsidy: a grant or gift of money: b : money granted by one state to another c : a grant by a government to a private person or company to assist an enterprise deemed advantageous to the public.

But if money is ‘something generally accepted as a medium of exchange (of goods or services), a measure of value, or a means of payment’

And if energy is a fundamental entity of nature that is transferred between parts of a system in the production of physical change within the system and usually regarded as the capacity for doing work,

then we have that a subsidy can only be granted by somebody to somebody else, if the former has got, obtained or cumulated some money and if money is a medium of exchange of goods and services and these goods and services can only be made with work and energy is the capacity of doing work, IT IS CRYSTAL CLEAR that only those having enough energy at their disposal can be in a position to grant a subsidy to somebody else.

If I am a naked ape and my only capacity of doing work is the energy provided by my metabolism, no one with common sense would expect that I can ‘subsidize’ the construction on Manhattan. As a naked ape, I can perhaps ‘subsidize’ my descendants, until they grow up and become independent.

As a primitive agriculture man, I could ‘subsidize’ perhaps a better living of a noble with a portion of my crops (energy from my animal force and my own arms, at the end) apart from ‘subsidizing’ to my descendants, but I could hardly ‘subsidize’ the Shuttle program, right?

So we are progressing and when we start with the mechanization and the use of steam engines (wood or coal), then, I can perhaps think in ‘subsidizing’ with this available energy (capacity of doing work and hence of getting money, the medium of exchange I obtain with the capacity of doing work), to lend this surplus of energy/capacity of doing work/capacity of ’subsidizing’ to somebody else to initiate the Panama Channel, but not so many other things we have in our modern global society.

And we finally end in a world burning 12 billion Toes/year, out of them, with 87% of them from fossil origin. I can imagine a ‘subsidy’ of the fossil fueled society to the nuclear industry. In fact, I don’t think that nuclear plants will have ever been possible without the power and mobility of the fossil fueled society lent to this industry. Still today and in the future. See Fukushima and what type of energy is being used to palliate or try to mitigate the horrors there.

I can imagine hydroelectricity systems being ‘subsidized’ somehow by a fossil fueled society, by using the capacity to do work, collect money representing the goods and services rendered and lending a part of the cumulated wealth. But I cannot imagine a hydroelectricity society ‘subsidizing’ motorways in the United States.

I even can imagine a agricultural society somehow ‘subsidizing’ the incipient coal generation systems, by providing the wooden beams in the mine galleries or in the rail tracks, but just in an incipient mode, but not to provide subsidies to maintain the 10 billion Toes/year fossil fuel society-

I see now much more, for instance, the oil industry ‘subsidizing’ the biomass production with several million fossil fueled tractors and harvesters and trucks and processing machines than on the reverse: for instance biofuels subsidizing the low cost flights worldwide.

Therefore, when somebody talks about “subsidies” to the fossil fuel systems and industry, it should explain what other energy source systems are DOING WORK to create wealth (money as a means of exchange) to lend somebody something from the surplus they generate, besides its own self maintenance (breeding system).
Though very successful, It is a boring and flawed mantra, created by the renewable cartels, to state that fossil fuels do not internalize their environmental costs, and that renewable DO NOT NEED to internalize, because they are ‘clean’ in themselves. Come on. If EROEI of a given system is, for instance, 5 and life cycle is 25 years, this means that present society (87% fossil fueled, not to forget) is providing a five years up front advance payment (precisely consisting in 87% of fossil fuels), that also have to be internalized EVERY 25 years.

If fossil fuels had to “internalize its costs” we would not be speaking here in a 12 billion Toes/year fossil fueled society.

There are energy systems that can maintain a given society for decades or centuries and there are energy systems that will never be able to maintain this type of intensive type of consumerism society.

Biomass reigned for several million years as the only energy source for humans. When coal started to be used massively, it took this energy source from lithosphere less than one century to take over in volume, density and versatility to biomass to DO WORK, CREATE MONEY (a medium of exchange goods or services created with WORK) and enable somebody to lend at higher level than with biomass.

Then, when oil started its massive use, it took oil less than one century to take over coal and biomass as the main energy source in volume, density and versatility, additionally, at consumption levels never before experimented.

But gas, hydroelectricity and nuclear power are known as energy sources since 150 years (gas and hydro) and about 70 years (nuclear) and nobody with common sense would expect nuclear or hydro to replace fossil fuels in volume, density or versatility.

Photovoltaic effect is known since half of last century. Wind energy is known since more than a century. And one cannot see in the horizon the day in which they would be able to DO WORK to take over fossil fuels at perhaps a level of 15 billion Toes/year. The alibi that they need ‘subsidies’ and time to take off, is already wasted and lacks credibility.

When some people will understand that money CANNOT DO WORK and that is only a representation (medium of exchange) of the goods and services created by the ones that have the capacity to DO WORK? Here it is the clue to who can subsidize who.

Here's another great post, thanks Pedro. The idea that systems exist off of storages, and that complex systems need bigger storages than simple systems is apparently a foreign concept to most people. Using net negative renewables such as solar just uses up the storages faster. Transformity (5th law) says that we shorten the cumulative length of the game the more we steal other gamepieces (from storages, from other countries, wherever). Bargaining and denial can be costly defense mechanisms.

Money is just a symbol of exchange; we will find out just how much our stolen gamepieces are worth when the petrodollar goes poof. At that point, solar vs. wind may be a moot debate, since we've been stealing everyone else's gamepieces so long that we think that 60+% of our oil that we import from other countries is our God-given right.

When we talk about comparing subsidies given to the fossil fuel industry and the renewable industry, we are talking about costs outside of retail prices that are paid for by our taxes. The US has spent over a trillion dollars to bomb and subjugate the peoples of other countries that have oil we want. This is not an externality in the typical sense of something that does damage to things outside of the production and consumption process. (Well, the damage to other countries is an externality, but we're not paying to remediate it.) Rather, it is part of the cost of obtaining oil, but is shuffled off to another part of people's personal budget (their tax bill, and the country's debt) instead of being part of the price at the pump.

This shifting of costs in the expenses sheet distorts the market, and that is the point of the subsidies argument. The relative market prices for fossil fuels and renewables are not necessarily reflective of the relative EROI, because the relative level of tax-based redistribution of energy resources to both is not equal. (Relationship of price to EROI isn't linear either, but that's another subject.) It is quite possible that if all the tax-based subsidies for all energy industries in the US were eliminated right now, that renewables would be the cheapest energy option. Hard to say for sure, but possible.

We have other two or three other options besides throwing trillions of dollars down the toilet trying to maintain a fossil fuel based economy forever. We could eliminate all tax-based subsidies (including military adventures) and allow the market to decide where to invest. Or we could recognize that the fossil fuel civilization is both unsustainable and ecologically destablizing, and we could use our energy surplusses to build a new, non-fossil fuel infrastructure. Or we could do some combination of both. But the current policy (in the US at least) of redistributing energy surpluses to the fossil fuel industry by government fiat is a corrupt and foolish boondoggle.

Your post is essentially a giant strawman. No one is disputing that at the current moment in history our real energy surpluses come almost entirely from fossil fuels. It is a question of how we should invest those energy surpluses to end up with something different in the future.

The giant strawman is to recognize that fossil fuels are providing almost all of the surpluses to this society, with which to pay subsidies for different activities and deny that they have anything to do with EROEI. The question IS NOT where should we invest, when we are talking about EROEI. The question is that fossil fuels today generate the energy to extract themselves and BESIDES power the whole world, thus proving that they still have a high EROEI, sufficient to exert this power. Something that is far from happening with modern renewables.

And of course, what is a diversion is to confuse the morality of spending the surplus of the fossil fuel society in paying costly wars for resources, with the reality that fossils CAN do these horrible things (wars for resources to pay their own extraction, transportation and seccuritization), and ADDITIONALLY still continue poweringt the world and modern renewables CANNOT. I am neither advocating for wars for resources. I would, of course, prefer to invest in renewable systems, rather than in wars, but this is a moral issue; nothing to do with the ability to power a given model of society that demands for that a high EROEI

I don't think it's sensible at all to separate the extreme wasting of Fossil Fuel energy into these resource wars from the particulars of EROEI. They are different faces of the issue, but they are highly relevant to the conditions under which Oil is and will continue to be available to 'us', and these are conditions that surely do NOT apply to the renewables we are comparing them to. Not to nearly the same degree, anyway.. Yes, renewables require resources, but many of those are then recyclable once they've been extracted and processed initially, and so it's not just the 'degree' of sourcing, but the very nature of it that fundamentally changes from one where you are mining the Fuel, to one where you are mining the Tool, and the Energy gets delivered for free, thereafter.

It's fairly LIKELY that we will have to continue finding strongarm methods to play the Great Game of Oil Acquisition, and hence, spend generously from that rich Energy Excess that this very fuel source brings, ("The Medium is the Message" Marshall MacLuhan) .. while it seems similarly UNLIKELY that there will be significant warring to be inspired by Solar and Wind, and in particular, the kind of solar that has a Couple Kilowatts on the roof and a handful of Heat Collectors, distributed broadly and at a very low energy density across many homes and businesses. Low Pressure, High Utility. *(But Peace is Boring and hurts the GDP, as we all know)

That is only a 'moral' issue because it has the PRACTICAL result of creating far less need for the externality of resource warfare, and the corresponding reduction in wasted materials and fuels and lives that go with it. It's not just that FF 'can' accomplish that output and still have plenty left over to power our Bidet Heaters and Nintendos, but that those 'Extra Energy Expenditures' have been INTRINSIC to this form of energy pretty much since we've used it. THERE WILL BE BLOOD, will there not?

"A typical location within the U.S. gets an annual average of 5 full-sun-equivalent hours per day. This means that the 1000 W/m² solar flux reaching the ground when the sun is straight overhead is effectively available for 5 hours each day. Each square meter of panel is therefore exposed to 5 kWh of solar energy per day."

This is not... no that's not how it works.

I stand by the statement. This is a useful way to characterize solar potential. Of course the sun does not come in a 5-hour dose at 1000 W/m², but that's what the word "equivalent" means. The NREL "redbook" database uses this convention in their characterization of solar site potential based on their 30 year study.

I stand by the statement. This is a useful way to characterize solar potential.

It is a broad, napkin way to characterize solar potential.

Because it is merely based on multiple averages, you need to drill deeper to get a really useful indication of solar potential.

If you have an argument, quantify it, you need to drill deeper. It is easy to quantify solar potential. It runs from 1.1 kWh per year per installed watt to 2 kWh per installed watt. This assumes a stationary system. One must compare their location and subsidies to their current utility cost to understand the financial value. Solar potential is based on competition. After all, it's just a newer way to produce stationary energy.

I look at this issue a bit differently but find the idea correct in practice. If we model the average 240 watt solar module at a mid US latitude we find a standard ~1.4 sq. meter panel producing 360 kWh of energy per year or ~257 kWh per square meter per year. If we take the NREL average of 5 hours of sun energy at 1000 watts per square meter we find 5 hours * average solar conversion of 15% * 365=273 kWh per square meter per year. This metric is low in the Southwest and high in the Northeast but as an average, it's correct.

I'm not sure I get the arguments of those who claim the ROI is not there.

I live in Western Australia, which also gets broadly the same 5 effective sun hours per day.

My 1.5kW System cost \$5600 to purchase and install - at the time I put it in I wasn't eligible for the subsidy - so that's my full cost.

1 kW (Unit) is currently priced from my power provider at \$0.22 - this is assuming at no point I am generating more power than I use - so I'm not including the Feed in bonus. Thus my system is generating a return of 7.5 * 0.22 = \$1.65 per day. Thats an annual return of over \$600 - or 10%.

My actual return is higher than that, as my maximum power generation happens to match up with my minimum power usage during the working day (while the house stands idle).

OTOH you didn't install your system to earn you money. You may have done it for a variety of personal reasons: peace of mind, doing your part for the environment, you're a geek who enjoys such toys LOL, etc. All are good reasons because they are your reasons. Perhaps a mate will tease you about how his savings having generated a much better ROI that your system. But when he's sitting in the dark with no power he won't be able to read his bank statement. And at such a time you system may be saving you a lot more than \$600/year...could 2X or 3X as much.

And most importantly, your Fosters will be icy cold at a time when your mate won't be able to find his in the dark. Congrats again!

Take all your points, for sure.
But if I keep my financial investment and spend most of the yearly returns on electricity cooling my Fosters, then at the end of 9 years my bank craters, and I have no Fosters and am in the dark, what to do next?
I must be missing a cog somewhere :(

phil - Exactly. It might not make financial sense from a ROI calculation but that's not necessarily the most important aspect. Like the old question: what's a 12 oz can of Coke worth? Depends...are you in the middle of the desert and been without water for a couple of days. At that point the ROI of your soft drink investments really isn't that important. I also put a lot of value on self satisfaction. Back when I owned a single family unit I could afford to pay someone to cut my grass. But I always enjoyed doing it myself: an easy dose of satisfaction. I see many such green projects where the personal sense of accomplishment is also an important factor to take into consideration.

I see what you mean - and not being an economist that basis you use is quite possibly right but it's not the one I used when doing the numbers myself.

I was taking it as an investment - my \$5600 of Capital is earning over 10% per annum (in actual fact I am actually getting about \$800 per year so it's nearer 15%. That investment is actually adding to the value of my house - and thus I'm thinking of it on more a 25year than 10year horizon. On that basis the annual writedown is only \$5600 / 25 = \$225. Taking that from my current \$800 gives me "profit" of 580 - or again about 10%.

My other reasoning was that over the last few years power prices have been going up at over 20% annually, and I can't see that stopping for a while. With that and a newly introduced 100% Feed In tariff - it's actually worked out better than I hoped.

Yeah, 10% is the magic number for me when it comes to household projects like this. It's nicely above my personal cost of capital so at least I'd not be actually losing money.

Every year or two I like to do the calculation for solar PV, because aside from the price it is really appealing. Even though it is fairly hopeless that it will ever work out in Canada. Electricity at \$0.22/kWh would certainly help the case, but perhaps you got an uncommonly good price on the system as well? solarbuzz.com has the current average price of a 2kW residential system in the US at \$14k excluding sales taxes, meaning that even in a sunny climate it's too expensive until the price goes well over \$0.30/kWh.

Solar is really cheap here - judging from the Kiwi and Stateside prices I've seen quoted here.

The people who did mine (www.solarunlimited.com.au) will now do 8 x 190W Suntech Panels with a SMA Sunny Boy Inverter for \$2990 Installed. I did go for the upgraded Inverter (3kW) in case I wanted to add extra panels later.

I've seen setups for as cheap as \$1991 believe it or not (http://www.awomansspark.com.au/?page_id=304), with 3.0kW for \$6990.

2 kW for \$14,000?

8 KD-240GX PV panels, \$448.80 each, total \$3,590.40

2800 W, Xantrex GT 2.8 Grid Tie Inverter: \$1,928.75

Retail cost of major components: \$5,500

One can find cheaper PV panels than top of the line Kyoceras.

\$14,000 for a 2 kW system is a ripoff. Someone is getting paid far too much for installation.

It seemed expensive to me as well, but if you follow the link, the 2kW system also apparently includes a battery backup.

Well, if one is going to splurge on a grid-tied system with battery backup for the few times the grid power is down, the price will rise skyward. Even so, 16, Crown L-16 batteries to source 120 VAC at 20 A cost an extra \$4,900. It would be cheaper to buy a diesel generator for a few hundred dollars to cover power outages or eliminate the desire to consume copious power without interruption. A grid-tied system with copious battery backup will never make economic sense.

16 Crown L-16 batteries would give about 40 kWhs, right? A generator would take about 4-5 gallons of diesel to generate that, right? So, you've got the cost of a generator, and maybe 50 gallons over 10 years?

If you're feeling guilty about using diesel instead of electricity, just donate \$3 to a Climate Change mitigation organization for every dollar you spend on the generator and diesel. You'll still save a lot of money, and the world will be a much better place overall.

A diesel generator is ~50% efficient, so I would estimate ~2 gallons of diesel fuel to generate 38 kWh of electricity.

enthalpy of combustion of diesel fuel: 135 MJ/gallon
38 kWh * 3600 s/h = 136 MJ

I think a gasoline powered generator would use about 4 gallons of fuel.

Are you sure that a small, home-sized diesel generator would be that efficient? That would be amazing.

Would you happen to have a link/source for that?

Our diesel averages 26-27 kwh from 2 gals. of B50, about 10% more on straight diesel, this on a steady state battery charge and a few variable loads (three cyl. water cooled Mitsubishi rated at 12kw, 1800rpm). It seems to have a "sweet spot" around 7.5 kw, using about 1/2 gal. per hour. This is much better than our old air cooled diesel. At full load (about 11.5 kva, clean) it uses about 0.9 GPH. Larger diesels are more efficient than these little guys, especially at near full load.

Nick, you are correct that my efficiency is too high. I looked at the wrong data to arrive at 50%.

Well, thanks for checking that!

But m0st folks look at your economics different than you.

Actually, most people who are skilled in finance look at it exactly the way he does. Each year he's getting a 10% ROI - that's a great ROI.

At the end of 9 years he's gotten 10% ROI for all of that time, plus he still has his original asset.

Another way of looking at solar PV is in terms of W/m2 it can deliver; from what the author states in his post, you are getting an average of 200 W/m2 of solar coming in for the US (lucky you, we only have 125 W/m2 in Switzerland). Multiply by 15% efficiency and you get 30 W/m2.

Now do the math - the US is a 10'000 Watt society - if you want to get 10'000 W from solar (some time in the future, when fossil fuels are gone), you need 330 m2, which is quite a lot. Of course you can argue that you might not need quite as much because some of the 10'000 Watt is wasted in conversion, but this is the ballpark number, and it is big. For me it means that you should care whether you get 8% or 15%, because 8% makes you need nearly twice as much area, which you don't have readily available, even with McMansions.

As for the guy saying EROI all over this post - there is more to renewables then EROI. One big issue is land use; All renewables have low energy density when measured in W/m2 that you can harvest, and solar PV has the highest energy density of all of these. Of course wind is great, but again - do the math - if you are limited in the end by available land area, you need to go with higher energy density systems (which incidentally is also a reason why biofuels are a nonstarter). This is very nicely discussed in David MacKay's www.withouthotair.com - well worth the read!

Both technologies are about in the same ballpark. Also, you must be very careful about the claimed efficiency of PV. Real life operation tend to be significantly lower.

"Also, you must be very careful about the claimed efficiency of PV. Real life operation tend to be significantly lower."

A few month ago, I was in a conference about green optics. There was a few designer of PV system (all variant). We have learn is that laboratory performance are calculated on mm2 surface and these drop on macroscopic cell. As I said many time, I have nothing about the development of PV but this is far to be the marvellous technology that some think it is.

Solar panels often come with so called 'flash datasheet' which is a report of the panel' real performance under controlled conditions. The buyer therefore has a guarantee that it's panel will perform within the margins as stated by the manufacturer under 1000W/m2 conditions. These flash datasheets are often used to optimize individual strings by matching similarly performing panels.

Also, field test data over 20 years from ISE institute in Freiburg (part of the famous Fraunhofer institute) shows very little performance loss over that period, so the 80% power warranties manufacturers provide for 20 or 25 years seems very conservative.

Perhaps there is a possibility that the manufacturers simply deliver what they promise in their datasheets?

I think there are a few kickers for the naive.
(1) Panels are rated at a cell temp of 25C, whereas full sun operating temps are usually 30C above ambient temps. That will cost you roughly 15% off rated power.
(2) You have DC to AC loses, and mismatches etc.
So you probably are getting maybe 75-80% of nameplate performance. If you don't understand that going in, you might think you've been cheated.

This is why some of the best solar results are achieved with arrays that get snow reflection in wintertime. They end up with more than 1000W/m2 shining on them when the temperatures are coldest, and production ends up being best when you'd least expect it. Gotta size the wires big enough for the extra power though.

You are right, but unless your aprety far north or have a tracking system, you will not get much of the snow reflection. However, this effect is perfect for vertical solar wall. Perforated solar wall are now becoming one of the standard way to improve the energy efficiency of a building. Also, there is now research to place domestic solar heater on a wall instead than on a roof. This will help to balance the production over a year, while easing the maintenance.

Testing a Thirty-Year-Old Photovoltaic Module

I hooked up the 54-watt blower directly to the panel. Wow! The blower started spinning at a fast clip. According to the Fluke multimeter, the blower was drawing 2.5 amps from my ancient solar panel — more power than would be expected from the factory specs.

I described my test to Raju Yenamandra, the North American head of sales and marketing for SolarWorld, the current owner of the old Arco Solar factory in California. “That’s unbelievable,” said Yenamandra.

When I explained that the outdoor temperature was rather cool, and the sky was unusually clear, Yenamandra did some quick math. “Well, it’s possible for you to get a 10% boost in performance due to the cool temperature. So, 33 watts times 1.1 is 36.3 watts, divided by 14.6 volts is 2.48 amps. That explains your results. Your module is still performing to factory specifications — or perhaps a little better. That’s very good. We usually tell people to anticipate a performance degradation of 0.27% per year.”

When I told Yenamandra that the PV module’s serial number is 256387, he informed me that it was manufactured in 1979, during the very early years of Arco’s PV manufacturing history.

... My old module shows no signs of browning, electrical corrosion, or water intrusion. It certainly looks as if it’s ready to perform for another decade or two.

“A PV cell is a rock that makes electricity,” said Davidson. “Unless something corrodes the electrical contacts, it will still keep working.”

I don't see what's not marvelous about that. I don't pretend that it's magical or it's a cure-all.. but it seems unquestionably reliable and useful, and hardly needs another 10 years in which to Prove itself.

I gave up on this guy, Bob. His unsupported and often incorrect claims are numerous and some of my challenges have been removed, probably because the threads became snarky :-/ So it goes.....

I didn't even start ;)

NAOM

Agree. Thx, G.

you can argue that you might not need quite as much because some of the 10'000 Watt is wasted in conversion<./i>

That's exactly right.

but this is the ballpark number

The ballpark number is less than half. 2/3 of electrical generation is wasted, 3/4 of oil used for transportation, and 2/3 of fuel used for space heat.

Again, the argument that solar PV or wind energy systems have the advantage that they are producing electricity directly and therefore, the equivalence with fossil fuels needs to be adjusted in this transformity direction, is a flawed and biased argument.

If you look at a Sankey Diagram in any important and developed country, or in the world (for instance, the world as a whole in 2005, were 509 EJ of primary exergy. World Economic and Social Survey 2011), you may notice that electricity is only 54 EJ of final exergy. That is a minimum part. To get this, the world needs to spend, effectively, 189 EJ in fuel use as secondary exergy.

In this direction, it is obvious that 1 EJ of energy produced by wind or solar theoretically replaces 189/54 = 3.5 EJ of fuel use, mainly from fossil fuels. The transformity is 1:3.5 in favor of modern renewables.

But if we want to look at the world as a whole in a holistic view, we cannot stop in replacing the present electricity use. We have to look at the total final exergy of 341 EJ, from which 341-54= 287 EJ are finally consumed in a non electrical form.

This is what the cartel and lobbyists of modern renewables avoid to talk about. This implies a “reverse transformity”, because if we want to do these activities with electricity, we have to spend 1 EJ of electricity to get a carrier type of energy to proceed to power the following activities, with probably losses that at the end give a transformity much lower than 1/3.5 = 0.28 EJ of final exergy:

54 EJ for Diesel engines (heavy mining or civil works machinery, land heavy transportation, buses, trucks, trains, etc.)
34 EJ for Otto engines, now not electrical.
10 EJ for aircraft engines
7 EJ for “other engines”
26 EJ for oil burners
47 EJ for biomass burners (many of them in places where electricity networks not even exist)
43 for gas burners in processes where the transformation into electrical ones is not so immediate.
28 EJ for coal burners, for instance for blast furnaces, smelting processes or heating systems, also not easy to replace by electrical systems.
31 EJ of mainly fossil fuels for non energy needs (plastics, pharma industry, fertilizers, pesticides, etc., etc.)

Military energy consumption, one of the most intenses in fossil fuel use, is not accounted here. Tell the military to go with hybrid armoured cars to the war or with hydrogen powered aircrafts or with electric tanks.

Therefore, if we want to consider modern renewables (mainly wind and solar, which are just producing electricity) as the future sources of energy for all activities and not only as a substitute of present electrical uses, when fossil fuels either deplete well ahead their respective post peaks or because we believe we cannot continue polluting more the environment with fossil fuels, we have to address also these types of “reverse transformities” and put them in the global, holistic calculations.

Not only that, but we have to think in the energy to be spent in transforming or replacing all the present existing human infrastructures, prepared to burn fossil fuels in an 87% of all the primary energy we consume at the level of 10 billion Toes/year in electrical networks. This is a burden that we have to add to the electrical “solutions” if we do not want to cheat ourselves playing to the solitaire.

Pedro

* The fossil fuels subsidize wind and sun, yes.

* But of course the fossils had the first subsidy, long long ago, from the sun. Exxon is rich not because fossil fuels are glorious, but because they are mining ancient sunlight.
Let's cast our eyes wide enough to see the full chain here.

It's sunlight all the way down.

As for reverse transformities in replacing existing direct use of oil/coal/gas, you must be aware that many "electro-technologies", that is, the direct use of electricity is far far more energy efficient. Indeed, electro-technologies are rapidly replacing direct use of fuels in many of the categories you cite above.

So, it's not at all clear that reverse transformities are as big a stumbling block as you suggest, given how inefficient many ff apps are today.

Randy,

I fully accept your comment. Sun has first subsidized the existing fossil fuels, no doubt.

And I should have perhaps specified that fossil fuels subsidize now the wind generation systems and the solar PV and CSP systems, rather than subsidizing sun and wind in themselves.

I realize also that some categories I have mentioned are more efficient when transformed into electric, for some specific activities. But there are still many, that they are not. I am not even sure that the given-for-granted electric private cars will get through.

The impressive photos that anyone has placed below, do not really impress me.

I am much more impressed by the Sankey Diagram of the world showing the REAL WORLD categories and uses in non electrical form rather than the wishful thinking dreams of the future.

And certainly, aviation, mechanized agriculture, armies, merchant and fishing fleets, and a lot of heavy machinery in civil works and mining, despite the photos, are still not electrical and could hardly be thought in changing them into electrical massively in the next decades. Thermal uses or smelting processes are also complex to change, specially when the consumption takes places in Northern Hemisphere, far from sunny places, despite of the wishful thinking theories of world electrical HVDC grids/belts.

I am now in an exclusive residential center of Sao Paulo, a city with over 13 million people. Many of the condominium skyscrapers have emergency generators (guess what: fuel powered) to give service when the electricty fails (very frequently) in the economic capital of the sixth or seventh economic power of the world, that is Brazil today. And the importance of having electricty without failures is becasue this suburbia was built on a swamp and they have to permanently pump up underground water, if they want the buildings and their foundations to last.

Many billions have no electricity and almost no hope of having it and we are here discussing the sex of the angels. I have been in many regions where there is no electricity (and no plans to have it), but swaying trucks or buses or pick ups or even small and dusty motorcycles take essentials (meaning by essentials medicines, bread, potable water, clothes, or a doctor to attend a pregnant or the pregnant to reach a doctor on time) to people in remote regions. It seems that we do not care about how the world is really composed, in this selected energy club.

I have been working for several years in bringing a HVDC from Northern Africa to Europe to be generated with renewable energies and it is a little bit more complex than showing a wishful thinking photo of a plane with its wings filled with cells.

a lot of heavy machinery in civil works and mining, despite the photos, are still not electrical and could hardly be thought in changing them into electrical massively in the next decades.

Well, the world had no problems to develop and produce all this approximately 70 years ago within only a few years and with far less people and less automation and lower technology level and constant bombardment etc:
http://en.wikipedia.org/wiki/Military_production_during_World_War_II

 System Allies Axis Tanks and SP guns 227,235 52,345 Artillery 914,683 180,141 Mortars 657,318 100,000+ Machineguns 4,744,484 1,058,863 Military trucks 3,060,354 594,859 Military aircraft total 633,072 278,795 Fighter aircraft 212,459 90,684 Attack aircraft 37,549 12,539 Bomber aircraft 153,615 35,415 Reconnaissance aircraft 7,885 13,033 Transport aircraft 43,045 5,657 Training aircraft 93,578 28,516 Aircraft carriers 155 16 Battleships 13 7 Cruisers 82 15 Destroyers 814 86 Convoy escorts 1,102 - Submarines 422 1,336 Merchant shipping tonnage 33,993,230 5,000,000+ Other: Pillboxes, bunkers (steel, concrete - uk only) 72,128,141 tonnes 132,685,348 tonnes Estimate Concrete runways 10,000,000 tonnes

There's no reason why the world should not be able to produce less machines in 50 years from now. Mind you: Machines which will actually produce something, reduce operating costs and deliver a return on investment without killing millions of people and infrastructure and housings.

I have been working for several years in bringing a HVDC from Northern Africa to Europe to be generated with renewable energies and it is a little bit more complex than showing a wishful thinking photo of a plane with its wings filled with cells.

Well, I could have told you long ago that Desertec is not worth pursuing, considering the fact that Europe does not lack any roof area and has plenty of own and low cost wind and hydro resources and a tremendous efficiency potential.

Oh, I see. Perhaps you could send your opinion to the German promoters of the Desertec idea that have invested for years many millions in the concept and now, as per your vague statement, they aparently have not realized that they were totally obsolete and outdated.

Does Europe has plenty of hydro resources still to develop to dismiss bringing renewable energy from Northern Africa? Please cite present levels and plans to raise them up, because at least in Spain we have already exhausted more than 85% of all the basin possibilities and we are covering just a 10% of the present electricity in a good hydrologic year). And as for wind, we have reached 17% of our electricity (more than Germany) with 20 GW installed power and Germany has even less with 27 GW and they both seem to be very much curving –flattening- the growth, for lack of either proper wind fields or lack of adequate subsidies (being the later what it is blamed more by Spanish promoters)

First of all: It's not just about renewable energies: The efficiency potential is actually tremendous.

People do a lot of useless things if they are getting paid for it. Governments invest billions in a particular fusion reactor design even though it most probably will never provide affordable electricity.
Desertec is also an excellent excuse for European policy makers to not invest in renewable power options at home and thus they have an alibi to protect the interests of the utilities which are currently in power.
Needless to say that Morocco could produce enough power with (waterless) wind farms to essentially power entire Europe: http://www.riaed.net/IMG/pdf/L_energie_eolienne_au_Maroc.pdf
Yet, Desertec promoters mainly mention much more costly solar thermal plants with absurd cooling water needs in the deep desert.

Hydro mainly has to provide power not energy to offset variable demand and variable wind and PV input. Hydro currently provides 22 days of storage capacity across Western Europe: http://www.claverton-energy.com/european-hydro-capacity-compared-to-the-...
There are no dead-calm periods and nights which combined last 22 days across Western Europe.

Germany can produce 65% of its electricity demand with onshore wind according to Fraunhofer: http://www.energiegipfel.hessen.de/mm/IWES_Potenzial_onshore_2011.pdf
And the European offshore wind potential is almost 2 orders of magnitude higher than that: http://www.ewea.org/fileadmin/ewea_documents/documents/publications/repo...
Germany also has already a roof area of 2300 km2 which is suited for solar power: http://www.solarserver.de/news/news-7381.html
This is enough to provide over 50% of the German electricity demand with German sun conditions.

The reason why particularly wind farms have a hard time in Germany is because policy makers have placed height and location restrictions on wind turbines. Unfortunately people like you who come with absurd studies and a barrage against renewable energies give them and the PR-agencies financed by the utilities ample munition to prevent renewable power plants from displacing their FF power plants.

Besides that renewables and efficiency measures are primarily needed to reduce fossil fuel consumption and not to entirely replace them by tomorrow. And besides that biomass-waste plants and wood-furnaces are also renewable by definition:

New and renovated buildings need far less heating energy than old buildings and even people in badly insulated buildings can always opt to dress for the season: Old oil-furnaces won't be operated with expensive oil in 50 years form now, but with heat-pumps, which are already available today and produce 4 times more heat per input energy.

Electrical commercial cars are already available to today and require a fraction of the input energy of the best-selling IC-cars in the US.

in 50 years from now the best-selling car won't look like this anymore:

and renewable energies will neither have to come-up with the energy to move such a behemoth with a single office-worker in it, nor replace 95% of their primary energy consumption, which is currently lost in the exhaust and cooling system in city-driving.

Electrical mining trucks already exist today and the input energy is again significantly smaller than for conventional diesel trucks:

As opposed to you and apparently the majority of the policy makers on this planet, I don't consider it wise at all to continue to invest a 100 times more in militaries and wars than in renewable energies.
But be it as it is: The military is already using renewably powered satellites: Future unmanned-aerial-vehicles will probably also at least partially be PV-powered to increase endurance and range.

And diesel-generators which will at least partially be replaced by renewable power plants not only reduce the number of deadly fuel convoys but also produce cheaper electricity:

http://money.cnn.com/2011/08/17/technology/military_energy/index.htm

One out of eight U.S. Army casualties in Iraq was the result of protecting fuel convoys.

and of course future armoured vehicles are in fact hybrid:
http://defensenews.com/story.php?i=4724127&c=AME&s=LAN

The hybrid-electric drive system saves on fuel costs and increases on-board and off-board power, said Signorelli. The company predicts the hybrid-electric drive system will provide up to 20 percent in savings in fuel conservation and a 50-percent reduction in moving parts, which means better reliability and easier maintainability, said Signorelli.

Tell the military to go with hybrid armoured cars to the war

That's exactly what they're doing with tanks, and they're very, very enthusiastic about it. The US DOD has announced plans to reduce oil consumption by 50% over the next few years.

we have to think in the energy to be spent in transforming or replacing all the present existing human infrastructures

Only if we do it before things wear out or are replaced. In the US, 50% of personal miles travelled come from vehicles less than 6 years old.

Tell the military to go with hybrid armoured cars

They are actually interested in that sort of stuff. For two reasons. One is lower observables, tanks running in ICE mode are very noisey, if they can run (for a short period) off batteries, they have some chance of not being spotted as quickly. Also if they can cut the amount of supplies needed to support them (logistics logistics logistics). Lastly the purchase cost (higher for the hybrid) may not matter so much to them.

Many of those direct uses of fuels, are very low thermodynamic efficiency. Burning gas or oil, to heat drying crops is a big one. Electricty plus a heat pump would be more efficient. Low grade solar thermal would be even better.

I am agreed, that electrical is only part of the current energy use. Most of these other areas can be whittled down as well, mainly by efficiency gains, but also switching from direct heating to electrically power heat pumps, which should be pretty efficienct at supplying lowgrade heat.

Crappy material like amorphous PV is fun to characterize.
I have a whole chapter devoted to in The Oil Conundrum

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What fun.

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What fun.

I have absolutely no idea what you mean by that.
http://img404.imageshack.us/img404/6684/tocd.gif

Sorry WHT;
The first time I went to that link, I was offered a "You don't have authorization to view this content" banner, and an requirement to register or join.. it was not the image you just linked.. can't explain what happened.

Still, I found your comment grating and inflammatory. Is that really the way to try to make a point.. one which was still not clear without a detailed exploration of that link? It seems that you're using some wonderful calclulus and analysis in order to continue making fairly unproductive jabs, for reasons you seem to prefer keeping to yourself.

If amorphous has serious liabilities you want to include in this conversation, is it so hard to just say that and a little bit of why.. then offer the link?

Rembrandt: "I think it’s rather impressive that we beat biology by a factor of 3 in just a few decades of effort (biology had much longer to work on the problem). Moreover, 15% is perfectly adequate for our needs, as we’ll see at the end".
1. Plants use solar energy mainly to evaporate water, photosynthesis is only a minute part of solar energy being used. About 250W/m2 in a forest could be used to evaporate water. Must better than our PV technology. Of course our biomass to electricity or to biofuels density power (W/m2) is worst (less than 1%, Smil 2008: Energy in Nature and Society. MIT)
2. Real PV systems have an efficiency of much lesser than 15% (electric watts per m2 of real occupation). For instance: Moura solar PV park has a module cell efficiency of 15%, but they land occupation is 250Ha and their expected production is 93 GWh/year (wikipedia and the plant owners data), taking into account the solar energy irradiated over the 250 Ha the expected electric power density will be 4,24We/m2 and a 1,39% conversion of solar energy into electricity. Other parks (fixed mounted) have better performance but still around 2-3%.
3. If we take into account the future necesities of storage systems for PV (probably with hidro-pump), then we will need more land, and then we will worst the density power, maybe balancing the future performance of cells efficiencies (an interesting subject to explore).
We are very far away of biosphere technologies, a forest beat humans by a factor of 50 in useful W/m2.
In my opinion, part of our problems as Civilization is our false perception that "we can beat" Biosphere technology.
In any case, the density power by PV (or CSP) is probably the best one of the renewables and much better than bioenergies, it is the only one that could be scalated-up over the TWe according to (Smil 2008)

Thanks for the caveats. I agree that hubris about our beating nature can be a damaging attitude. Nonetheless, algae in a bag get up to 5–6%, without evaporation and other distractions. It's the best that biology will produce. In realistic scenarios, bio efficiency is almost always less than 1% per hectare of land. So comparing actual deployments of PV would still come out ahead of this.

But these are distracting points. It seems we agree on the utility of PV, and you are not arguing that 15% efficiency is too low—which is the attitude I wanted to counter in the article.

Plants, converting sunlight to vaporize (transpire) water, is mostly a dead loss to the plant, and it has to suck up more water to replace it. Mainly they do it defensively to prevent damage from overheating.

No, nutrients go from roots to the rest of the plant thanks to the energy from the evaporation of water (like a pump, by osmosis). Also, Overheating and the response of plants is like your fridge, is not a "dead loss", but human military energy expenditures...

Thank you, thank you, THANK YOU for laying all this analysis out in a single posting. I'll be re-reading this one a lot.