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220 comments on An EROEI Review

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rohar1 on March 18, 2008 - 11:30am Permalink | Subthread | Comments top

The problem with thinking within EROEI is that although it's a good method to evaluate systems on paper, it isn't a wide enough scope to understand whether it's a good idea in the real world. These are some items from an essay I wrote a while back on evaluating renewable energy systems.

Factors for Evaluating Renewable Energy Systems

  • EROEI Energy Returned On Energy Invested which is the system energy output over construction and operation energy input. This is the term that is usually used in isolation when comparing energy systems, ignoring the rest of the factors.
  • Location Independence of the generation system. The construction energy of transport infrastructure and
    loss of energy during transmission is a major factor in total system feasibility. The closer the renewable power generation system is to the consumer, the more efficient the total system is. If the system is used to manufacture energy transport media, the distance the energy product needs to be transported is also important.

  • Scalability and Availability of construction materials and input media. If the required construction materials are rare or require a lot of energy to locate and process, this affects the efficiency of the system. If the system is built from common and recyclable materials the system will scale well. In the case of energy media manufactured from organic sources (like ethanol, bio-diesel and bio-mass),the scalability and availability of these sources is important. If the organic input media is a waste product and it may be converted into a usable energy product without a large environmental impact, the scalability is less important than the use of an otherwise wasted product.
  • Reliability: If the system output is intermittent (i.e.only producing power when there is direct sunlight or the wind is blowing) either an energy storage system needs to be incorporated or the system is limited to supplementary power generation. There is a limit on the percentage of intermittent electrical power generation that may be tied to the electrical grid before it becomes unstable.
    The guideline from the utility companies is at around 10% intermittent generation to maintain grid stability.
    The other portion of reliability is related to serviceability and generally the less moving parts and simpler the system the less chance that a
    component or the system will fail.
  • Serviceability: If the system is serviceable and individual components can be repaired or replaced the whole system has a better
    energy efficiency than systems that are not serviceable and need to be replaced completely at the end of there usable life span.
  • Environmental Impact: Although most renewable systems have a lower impact on the environment than fossil fuels, structures like
    hydroelectric dams usually require major disruptive changes to waterways and the local environment. The manufacture of the components may also have an substantial environmental impact and in the case of converting an existing waste product to fuel there may be a positive environment change.
  • Aesthetics and architectural design of the system are also very important to society.
  • Transportability: The ease at which an energy transport media can be safely transported and stored as well as the energy density of the media.
  • Implementation: The amount of effort required to convert traditional fueled systems to the renewable product.
  • Efficiency of Consumer Engine:
    The total system efficiency is affected by the engine used to convert the energy transport media to work by the consumer.

  • Complexity of technology and whether the system requires highly specialized equipment to produce and whether this equipment is
    available to the general public.

  • Intellectual Property ownership and other political factors affecting whether the technology can be
    replicated by the community or will be controlled by agencies that will arbitrarily set the market price once the system is in place.

  • Security: Large centralized power generation systems and processing/refineries are more vulnerable to major attacks than interconnected community systems. The Internet is a good model of a distributed system limiting single points of failure and is very difficult to completely disrupt.
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kdolliso on March 18, 2008 - 12:04pm Permalink | Subthread | Parent | Comments top

Some good points, Rohar1.

Let me add a scenario. Let's take a situation where the world market is Saturated with Sugar (pretty much like the present.) BUT, Country A (Brazil, say) has hundreds of acres lying fallow which Could be used in Sugar Production.

Let's do something different. Let's SEPARATE the process of growing the sugarcane, EROEI-wise, from the process of making ethanol. In other words, let's assign the cane it's own btu number, and a number for the EROEI of producing the cane. And, yes, let's consider the Solar Energy as a freebie. Would this help?

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ET on March 18, 2008 - 2:03pm Permalink | Subthread | Parent | Comments top

All good real-world considerations.

It's also important to realize that one cannot simply chain together EROEI calculations in a purely mathematical way. If that were possible, one could end up with the following infinite progression:

1 unit energy -> process producing 1.5 EROEI -> 1.5 units energy

chain this together a few times and you would get:

1-> *1.5 -> 1.5-> * 1.5-> 2.25-> * 1.5-> 3.375 giving a total of EROEI of 3.375 (or however far you want to take the thought experiment)

Giving the impression that if you chain up a number of ethanol plants and consider the whole system, you get way better than 1.5 EROEI. What is wrong with this picture?

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clifman on March 18, 2008 - 6:29pm Permalink | Subthread | Parent | Comments top

What wrong is that the equation utilizes ALL of the net energy from each step as input for the next iteration. Civilization, society, industry or a single organism trying to survive needs to access a portion of that net for other functions. That's why it makes a HUGE difference as we shift from 100:1 easy oil, when our industrial economy could utilize 99 barrels of oil to build stuff and bustle around like bees on ecstasy, to energy sources in the 10:1 range, where the non-energy producing part of the economy only gets 9 barrels to buzz around on for every 1 needed for re-investment in producing more. And that's why we won't be running an industrial economy (or probably any kind of civilization) on 1.3:1 ethanol, or any other low single digit EROEI source. Now some folks, like posters below who insist that $ matters more than EROEI, or that EROEI is some kind of religion that we worship, may not agree, but to me, this is a simple concept that gets grossly misunderstood or more often just ignored. We're not talking about the efficiency of a system or a process, per se(so engine efficiency is not comparable to EROEI). We're talking about how many barrels of oil (or of ethanol, or any other energy SOURCE) it takes to get more, leaving the balance for other uses - like growing food, heating homes, and transporting people and stuff. Once it takes all - or even most - of the energy just to get more energy, that is, as EROEI approaches unity, industrial society is screwed. I'm not here arguing whether that's a good or bad thing, but it will be a big thing. Some also try to debunk EROEI by comparing it to the generation of electricity. But that is comparing the conversion of one form of energy that is a source (coal, for example) into another form of energy that is a carrier (electricity). The electricity is tremendously useful to us, yes, but electricity itself is never a source for humanity - it is always generated from something else. Ultimately, there are only two sources of energy for humans - the sun (fossil fuels, solar, wind, hydro) and nuclear decay. I'm not a physicist, or anything close to it, so perhaps there's really only one ultimate source, but that's beyond the practical point I'm (very windily, I know) trying to make. As for where to draw the boundary in analysis, I say apply KISS. Picture a broad plain, a tribe of humans, a barrel of oil. They want more. They invest that barrel into the infrastructure to extract more from the ground. The work that one barrel does produces ten more. They take one and repeat the process, and have 9 left over to party with. This goes on for some time. But then the source rock gets stingy. Now they only get 2 barrels for each one invested. Party slows down. Big chief says, my father rode a camel, I flew a jet, son, you can still drive a car, but your son, when that one barrel allows us to extract only one barrel, will again be riding a camel. OK, I give up. It's a simple concept, I suppose folks will either get it or they won't. But we'll all be living by its impact, as William Catton laid out clearly way back in '80 in "Overshoot: The Ecological Basis of Revolutionary Change." (Oh, and sorry, ET, I know you're not one who misses the point, I merely took the opportunity of your hypothetical scenario to launch into my little rant...)

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ET on March 18, 2008 - 7:06pm Permalink | Subthread | Parent | Comments top

What wrong is that the equation utilizes ALL of the net energy from each step as input for the next iteration.

But that is exactly the point of my post. If we theoretically take ALL the energy output in a multi-staged process and apply it once again to the same process, we get, theoretically, an infinitely increasing ER on a given EI for the entire process. Obviously this cannot be even remotely real even if the math works out.

The larger point is that reality checks are always a good idea. When I see EROEI figures for solar PV of 10:1 bandied about, and look at the actual price, I know the figures are bullshit. Same with wind power.

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wkwillis on March 19, 2008 - 12:56am Permalink | Subthread | Parent | Comments top

Not sure that's true, and panel photovoltaic competes with me and my concentrating photovoltaic, partly. Mostly panel photovoltaic competes with distribution in a financial sense.
Most of the cost of photovoltaic is labor cost. Your are paying for the Ford F150 to haul the roofer around. In China the roofer costs less and travels by tram. Does that mean that panel photovoltaic has a higher EROEI in China?

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paal myrtvedt on March 19, 2008 - 4:56am Permalink | Subthread | Parent | Comments top

When I see EROEI figures for solar PV of 10:1 bandied about, and look at the actual price, I know the figures are bullshit. Same with wind power

We are on the same page ET.
My take on that situation is: Have the renewable-manufacturers utilize their own HOME MADE energy in all their necessary sub-processes (or as many as possible at least) and see where that bring them. Not far I’m afraid…

In the future when fossils are gone, we will be back to square-one and that is not a sophisticated square(!) I can see good old fashion windmills, various “easy” to make waterwheels some sort of sterling/steam-engine/generators and such driven by combustion
I have serious trouble to see modern WT-Nacelles and PV technologies made and maintained in that scenario, and by then their EROEI issues will be clear as the sun by midday.
In my mind we should develop “simple technologies” today, which are not focusing efficiency – BUT rather on simple functionality and easy to maintain demands (as good as it gets sort of thinking).

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kdolliso on March 18, 2008 - 9:00pm Permalink | Subthread | Parent | Comments top

Let the Non-Engineer, also, expound a bit on "Civilization."

Successful ones tend to be made up to some degree by "Successful" people. Successful people tend to NOT be "Wasteful" people.

Will a Non-Wasteful Person ignore a fallow, but fertile, field as a source of energy just because it's a little harder to get energy out of than a barrel of "easy" oil? Even when the "easy" oil is getting harder?

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roflwaffle on March 19, 2008 - 2:07am Permalink | Subthread | Parent | Comments top

I think that depends on what you mean by run the economy. Since oil is used at a practical efficiency of somewhere around a percent or so as long as we define it's use as that of personal transportation (for the most part) we have quite a ways to go in terms of smaller more efficient vehicles and to a less extent better drivetrain efficiency. If we define it as the transportation of people and tons of steel/plastic, then it's efficiency of use increases, but that's somewhat disingenuous since we could use even larger vehicles, say semis with 40,000lbs in the back, and see even higher efficiency of use because ICE efficiency tends to increase with load. What I'm saying is that we should look at efficiency from the point of view of consumption, not just efficiency for the sake of efficiency.

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Dan Browne on March 20, 2008 - 7:16am Permalink | Subthread | Parent | Comments top

You wrote a hell of a lot of unneccesary words to get your (one line) point across.

"Once it takes all - or even most - of the energy just to get more energy, that is, as EROEI approaches unity, industrial society is screwed."

And THIS is the problem with the understanding of EROEI being propounded here.

We're NOT going to get down to unity. Not even close.

Wind power, wave power, hydro power, Solar power. Even growing vegetables.
All of these have EROEI of anywhere from the low single digits to the high twenties.
(Look at the footnotes on the original post).

Thus while it is true to say that we will have to produce MORE INFRASTRUCTURE and use a larger share of our economy to produce energy than we did before it is patently UNTRUE to say we are inexorably sliding towards an unproductive 1:1 situation.

There is a FLOOR under us and it's the lower limit of renewables.

Now taking this to it's LOGICAL CONCLUSION: Even if the return on energy invested is only 20% then that means you only have to build five wind turbines or wave generators or hydro plants or solar panels to get one FREE ONE each year.

Now by compound interest of EROEI that means that at 20% you double your installed base approximately every four years. If from that 20% you use 10% for other things than building your infrastructure you double your installed base every eight years.

So back to the point: We need to build INFRASTRUCTURE.

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Engineer-Poet on March 20, 2008 - 9:42am Permalink | Subthread | Parent | Comments top

Even if the return on energy invested is only 20% then that means you only have to build five wind turbines or wave generators or hydro plants or solar panels to get one FREE ONE each year.

It also means that 80% of society's energy-production effort would be devoted just to obtaining more energy, and a mere 20% for the other things we need to do (like growing food).  If you can't re-invest all energy to increase your installed base, you're screwed.  On top of that, the source has to scale to nearly 5 times today's gross production for the same net.

Industrial society can't handle EROEI as low as 1.2.  I'll bet that anything less than 8 is going to cause plenty of pain.  Fortunately, most of our options are a lot better than that.

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Dan Browne on March 20, 2008 - 9:47am Permalink | Subthread | Parent | Comments top

EP,
I agree with your point. But consider it a little more.
Even at 1.2, if they use half of the energy for other things (and we'll NEVER get that low) then it only takes 8 years to double the installed base, 16 years to quadruple the installed base etc.

Now go back and look at the actual EROEI numbers on the original post.
Wind, Solar etc are WAY better than 20%. And we STILL have a bunch of oil to get us kickstarted.

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Engineer-Poet on March 20, 2008 - 10:13am Permalink | Subthread | Parent | Comments top

Even at 1.2...

... you have 80% of the effort of society devoted to obtaining more energy.

Not unlike the times when 80% of people worked on farms.

You don't quite grasp how enormous a dislocation that would be.  Industrial society needs more of a surplus than that.

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Dan Browne on March 20, 2008 - 10:36am Permalink | Subthread | Parent | Comments top

EP,

I do understand the idea of using 1.2 I used it as an illustrative example because it's easier for people to understand 4 windmills gets you one free than it is to understand 320 windmills gets you 160.

I said "we'll NEVER get as low as that". If people just take the time to read the links at the bottom of the original poster's post (as I have) you'll see that the WORST of the renewables is nowhere near as bad as 1.2

Anyways, what's the matter EP? Have you become a doomer all of a sudden?

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Engineer-Poet on March 20, 2008 - 4:18pm Permalink | Subthread | Parent | Comments top

I do understand the idea of using 1.2 I used it as an illustrative example because it's easier for people to understand 4 windmills gets you one free

The problem is that the claimed EROEI for corn ethanol is greater than this, and it doesn't scale at all (neither does it include non-energy losses like topsoil).  Using that as an example implicitly approves one of our most disastrous "energy" policies.

Have you become a doomer all of a sudden?

Hardly.  Just reminding everybody that there are a lot more ways to screw up than to get it right.

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Nate Hagens on March 21, 2008 - 11:06pm Permalink | Subthread | Parent | Comments top

not to be a doomer but:

1) i am uncertain how wide of boundaries those NREL EROI figures are - there is a good deal of infrastructure they may take for granted that is subsidized by oil

2) high EROI is great, but only part of the problem - we need high EROI that matches our current infrastructure. If we already had PHEV transport, rails, etc. then i would say that higher EROI solar would make oil a dinosaur. But clearly that is not the case. We need high energy gain consistent with what society is dependent on, OR high enough EROI to transition social infrastructure into a new era without too much pain

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r4ndom on March 19, 2008 - 1:06pm Permalink | Subthread | Parent | Comments top

What's wrong with it?

Nothing, really. The only issue is that each cycle takes a full growing season, and it assumes that all of the production from the previous cycle is put back into the next cycle.

This is nice if you are bootstrapping a new infrastructure while society runs on some other source, but reality means you have to use some of the surplus outside the system that's normally defined when considering EROEI.

Reality therefore looks more like:
Ein*EROEI-Eext->Enext
or:
1.0*1.5-0.5->1.0

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mdsolar on March 22, 2008 - 9:05am Permalink | Subthread | Parent | Comments top

You are expanding the sytem the whole time. For oil, you are drilling more wells and building more refineries. For biofuels you are putting more fields under cultivation and building more distilleries. All the time you are not getting any net energy for other uses. Once you stop your expansion and start using energy elsewhere, you are back to your original EROEI. I think that if you think it through in this manner, you'll find that you never get more than the original EROEI even if you cease operations and take all the product from your last harvest for use elsewhere.

Chris

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greenish on March 18, 2008 - 7:25pm Permalink | Subthread | Parent | Comments top

The problem with thinking within EROEI is that although it's a good method to evaluate systems on paper, it isn't a wide enough scope to understand whether it's a good idea in the real world. These are some items from an essay I wrote a while back on evaluating renewable energy systems.

Excellent list and spot-on. It takes a comment I was going to make and expands it quite a bit.

That comment was that while the "quality" of energy is frequently discussed, I haven't seen it described in a simple way. That could be useful; seems like up until now energy has been valued mainly by cost of extraction and processing, and not by it 'intrinsic worth' to hominids wishing to perform 'magic'.

And the term 'magic' is used by me here because that's sort of the ultimate standard: a substance with infinite energy that anyone could pick up and use with no investment and store & transport at zero cost, causing no harm to the biosphere. We don't have any such stuff, but clearly some energy carriers approach that ideal more closely than others do, and where they fall on that line would be useful to consider.

The listing is good and more complete than my top-of the-head one, which was:
energy density
ease/cost of storage at earth-surface temps and pressures
Moving it around: threshold costs, complexity costs, etc
what stuff can currently or in theory be done with it
level of complexity investment to utilize it (ie, chain saw vs. fission plant,)
Investment thresholds for obtaining and using the energy carrier from where it starts (ie, gathering firewood vs. deep offshore oil drilling)
toxicity to the biosystem, in extraction, processing, or from use
safety
reliability
etc

It'd be nice to be able to assign a "quality coefficient" to different sorts of energy, even if it wasn't perfect. Clearly, kerosene is closer to being "magic" than is burning cowpies, since you can fly a jet halfway around the world on it nonstop, etc.

This is the complement to EROEI which is needed....

Great post, and continuing kudos to Nate for his work as well, can't want to see the next batch of stuff.

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Nate Hagens on March 18, 2008 - 8:12pm Permalink | Subthread | Parent | Comments top

The problem is that 'quality' as defined by our current socio-political system is not the 'quality' that would be long term desirable or sustainable. We should set aside EROI for a moment and determine what type of society we can achieve post cheap oil - what infrastructure looks like. What the ecosystems look like. etc. This will then change the definition of quality - though I expect liquid fuels will always be valuable. But if transport fuels take up 1/10 as much % of our fuel mix in 20 years than they do today, the definition of 'quality' will have changed.

Next determine how much energy gain we can expect, not for next year but for next 100 years. This would require an analysis of best uses for the remaining high quality fossil stocks in order to turn them into renewables that could support the type of infrastructure in #1

Then we use net energy analysis as an allocation tool of how to properly allocate our energy stocks and flows into productive society.

We're kind of going about it backwards now - assuming that 'quality' is given by current conditions, and then bickering about which fuels have the better EROI, quality adjusted. Its the fixed cost nature of our current system that is the bugaboo. The barriers to change are so large that we will keep seeking liquid fuels without noticing we are destroying our life support systems to procure them

(p.s. Rohar -that is a nice list - all important things - tho energy surplus (via EROEI) is a biggie. Many of those things are also not accounted for in our present market system either - so 'energy analysis' as we speak of it has to include ecology and externalities.)

nice website too - if you want to write a guest post on that SHPEGS project let me know

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greenish on March 18, 2008 - 11:44pm Permalink | Subthread | Parent | Comments top

The problem is that 'quality' as defined by our current socio-political system is not the 'quality' that would be long term desirable or sustainable.

So true. I actually find the quality of undrilled oil & pristine environment higher than jet fuel, perhaps why I didn't work out long-term as a doodlebugger. My "quality" comment had only to do with one of the confounding factors of having a conversation about energy with present-day humans, which is often unavoidable. BTU's are a pretty gross metric.

Its the fixed cost nature of our current system that is the bugaboo. The barriers to change are so large that we will keep seeking liquid fuels without noticing we are destroying our life support systems to procure them.

Well said. We should probably be thinking more in terms of Planetary Choices Created / Planetary Choices Foreclosed (PCC/PCF ?) which would treat energy as a sub-category, and for that matter human activity as a sub-category. I'll try thinking up a way to sell that & get back to you....

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shrimppop on March 19, 2008 - 1:02pm Permalink | Subthread | Parent | Comments top

Elsewhere in the comments H. T. Odum is mentioned, as are the concepts of eMergy and Lifecycle Assessment (LCA) as analysis tools. Essential to understanding energy (according to the wikipedia bit on eMergy) is the concept of transformity or quality of energy. Elsewhere this appears to be related to the concept of exergy [Gibbs].

EROEI seems a useful concept specifically when addressing the dropping productivity of oil or other liquid or coal production. But I think the energy quality issue needs to be incorporated to avoid the twisted explaining away of Brazilian sugarcane EROEI.

Also, it is critical where you draw the system boundary in determining net energy, as the poster about LCA mentioned. I want to add the concept of energy yield [Mollison, Holmgren] to the discussion, that is, the net energy out of a system when all the systems energy needs are met. This is not, on the surface, different from net energy, except that it explicitly identifies the boundary / scale of the system as being a key determining factor.

Odum [The Energy Basis of Man and Nature] states that not all BTUs are the same- some have the ability to do mechanical work. This may be what the "economic value" folks have in mind. Odum proposes a Fossil Fuel Equivalent (FFE) as a way of converting all types of energy, as measured by heat (BTUs, calories, etc.) into a common base quality energy.

1 FFE =:

  • 10,000 uncollected solar radiation calories
  • 2000 sunlight calories
  • 20 gross plant product calories
  • 2 collected wood calories
  • 0.33 elevated water calories
  • 0.25 electricity calories

    These were written in 1976 so the conversions may be somewhat different today. But it clearly shows that the analysis of return and net energy needs to be broadened.

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    Nate Hagens on March 19, 2008 - 1:30pm Permalink | Subthread | Parent | Comments top

    Odum was a genius and I have learned a great deal from his work, and his students. But eMergy is something I just can't internalize-it complicates things even more.

    The graphs I post do not twist EROEI of sugarcane at all - they just show that some energy is used to process it that could have a different use.
    In the end, all we are trying to do here, with ecological economics, EROI, net energy etc. is to have more of a biphysical/ecological basis for our decisions. How we do that is of course important but I think we are still at the stage of convincing people it should be done.

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