Before you buy the solar system, have you thought about what $20,000 can do elsewhere in your budget? What would happen if you bought a Prius, and sold your existing compact to someone who promsied to junk their SUV? What would happen if you put in a ground source heat pump? What would happen if you sold your home, and moved right next to your work? I have thought about putting in a solar system, but the price just tells me that it is really for show right now: I get better bang for buck, whether in dollar returns or decreased carbon emissions, everywhere else. My next $20k investment, after my $20k in the Prius, is the GSHP. I suggest that you look at your carbon footprint, not just in natural gas or coal used to generate electricty, but also in transportation, eating, etc. Solar is in the works for us, just not for a while.
And, if you live close enough to work, consider buying an electric scooter for less than $3k. Replacing an SUV with a scooter will far outweigh the solar panels, in your pocketbook and for the environment.
From a social perspective. investing in Canadian Hydro Developers does more good. A bit over 7 kWh# of renewable energy (much of it hydro with 100+ year life spans) per share and growing as all profits and cash flow plowed back into development of more renewable energy (no dividends).
A changing emphasis to wind (but a couple of small hydro projects in development) and a biomass facility.
# Hydro production has 30% annual variability, wind 15%.
Good points, but I drive an 8 year old Honda roughly 5k miles a year, if that. I do need to bike to work more, but can and do at times.
Heat pump might be an idea worth pursuing...although heat isn't needed much here obviously it produces AC also. I'll be busy researching every option this weekend I suppose...
And yes to...Dave? below, looks like the payback for solar water panels is even better so I'm seriously thinking about doing that at the same time. My local utility pays extra for that (I think they convert BTU's to KWH and tack on 2-3 cents extra) but for PV power they give me a 5 cent credit for every KWH I would produce-that's over and above what their retail rate is.
But then again getting rid of the heater entirely and going with instant gas hot water would be nice also. My girlfriend would appriciate the extra closet space...
While you might be doing a grid-tie solution, I'm planning on going off-grid with my PV system. For me, it's not a matter of cost, it's a matter of having electricity no matter what happens to the grid, plus it forces conservation on my part. It also means I won't have an electric power guy on my land to read my meter, worry about having a licensed electrician do everything, etc, etc. I'm just crazy like that, though. ;)
Exactly, I can't imagine not having some storage on site. The grid will go down. Even 4 or 6 100amp hour agms would be a blessing in that case. We started with the battery bank first, with inverter, and charge the batteries from the grid. Easy enough to add an alternative charging source at any time.
"I'm planning on going off-grid with my PV system."
Why not install a grid tied with battery back up system? This would allow you to bank excess summer generation for winter use. The batteries can be sized to give you hours or days of backup power.
Not grid tieing will make your system less efficient as any surplus generation will be wasted rather than sold to the grid.
I am really curious why the systems are sized so large. Two people, maybe even include some kids, don't need a lot of power at any given time -- if you use low-wattage lights and turn them off when not needed, avoid power sucks like plasma-screen tv's, dry clothes on a clothesline, and so on.
If natural gas is available, it is surely more efficient in every way to use it as a primary heat source for hot water on cloudy days, heat for the clothes dryer when the sun isn't shining, space heating when solar is insufficient, etc. Turning gas to heat to make electricity to make heat makes little sense.
On the other hand, sizing individual solar installations to be big enough to run motors and compressors and other major power drains doesn't seem to make sense to me, either -- especially when you are already tied to a grid.
Why not assemble a system that takes advantage of all sources, using the best of each.
Use the home-solar for water heat, lighting, light electrical; gas for backup heat and cooking; grid for heavy electrical.
Natural gas is not available where I live. My electric service is already unreliable. I have regular short outages and a longer outage every time there is severe weather (which is more often these days). So far the longest outage was 44 hours.
I have a 360' deep well. When I lose electricity I lose water. The well is deep enough that the pump uses a lot of electricity (it uses 220V). Frozen food doesn't do well after 44 hours of outage, though I do intend to invest in a 0.5KWH DC freezer one I have PV panels up. I have a gasoline-powered generator for the longer outages now, but that's problemmatic in the long run.
The only option I see is about 4kw of panels and enough batteries to last maybe 3 days. However, before I do the PV, I'm doing solar hot water and a geothermal heat pump to replace my oil burner.
It's all going to be very expensive. However, the grid is only going to get worse. The outages will be more frequent, and it will take longer and longer for the repair crews to get out where I live. And I can't live without water (though I am investigating a DC pump...I'm just not sure there are any that can handle 360' with enough pressure to backwash my iron-removal system).
Everyone's situation is different. Most city people can rely on grid most of the time. Country and off-grid a different story, and different mix of resources.
Most people don't need much electrical power, and if you have battery backup, an unreliable grid is not so much of a problem. Lifting water 250feet takes some serious energy-- living where that is necessary obviously involves a whole different order of tradeoffs.
Seems like the poles of the spectrum are technological beauty or beauty of simplicity -- and a real-world solution involves certain compromises and certain aesthetic choices along that spectrum. Obviously, the choices will be different for everyone.
I'm still curious what kind of system you can get for $10K.
In Switzerland, imho, an it is very ho, what individuals can do to reduce ‘overall’ energy consumption, are, in the two unordered top positions:
1) insulate home to top standards. For the mass of apartment dwellers this means lobbying, arm twisting and paying more (transformations, etc.) facing Building Societies, large property owners, banks, etc. Not easy. Geothermal heating is a second point here.
2) reduce or eliminate meat consumption.
Now my at the mo. two top picks could be contested, and of course they are set in a business as usual scenario, etc. My point is not to prove I’m right, which would be impossible in any case, the numbers aren’t there, but to show that the first does bring financial advantages to the dweller (less spent on heating etc., even if very long term investment) while the second doesn't afford any advantages at all except socially, being pure about not eating beef filet, having success with veggie women/men, etc.
The links between drafts and icy beds and burning FF are quite direct, for the other - no. Typically, Switz. is enforcing very strict building standards and controls, rightly so, but the agri. circuit is not touched.
Difference is: upgrading or transformin housing is good biz - many will earn money. Down grading imports or meat agri. will harm importers, farmers, bison and ostrich farmers (considered green), meat producers, salt of the earth, etc. etc. so it can't be done.
Your advice is solid and although I haven't spent a lot of time examining the linkage between energy and meat (I'm not much of a meat eater myself), I do think we can do far more to make our homes and commercial spaces more energy efficient. It's painful for me to enter a shopping mall for several reasons, but I'm especially appalled by the amount of energy consumed by their lighting and a/c systems. Light levels in most stores is excessive, to say the least, and much of it is provided by woefully inefficient halogen sources. The ubiquitous 75-watt halogen PAR38 operates at roughly 15 lumens per watt. If store owners kept their existing fixtures and simply swapped-out these bulbs (micro space heaters) for the latest generation of halogen IR lamps that produce upwards of 25 lumens per watt, they could obtain the same amount of light for about 40 per cent less energy. Better yet, replace those fixtures with new ceramic metal halide lighting (e.g., Philips MasterColour Elite) and you would get similar or arguably better light and slash power and a/c loads by as much as 85 per cent. This is just one example of what we can do right now and at very nominal cost; the potential energy savings are enormous and when you look at the numbers, the financial benefits are resoundingly positive.
Another case in point. Several years ago, I replaced a 455-watt metal halide fixture in a retail store that ran 24-hours a day as a security light with a two-tube, low ballast factor, T8 fluorescent that operates at 55-watts (as a night light, the replacement was more than adequate). The change-out of this one fixture saves enough electricity to power my home's heat pump for the entire year!
With respect to geothermal heating, I'll simply add that we shouldn't overlook their air-source brothern. DaveMart and I have discussed this at great length in other threads so I won't go into the details here; suffice to say they're often much less expensive and can be installed with fewer complications and restrictions and in many cases will do just as good a job.
"Air source" heat pumps are very common in Asia, where in the most populated areas, the temperature rarely drops below freezing but might be in the 32-55 degree range. This could be appropriate for California, Georgia, etc.
They work as both air conditioners and heat pumps. Try the Duskin brand for example. Matsushita also makes them.
Paul, you know me, I nearly mentioned air heat pumps, but with the high humidity and need for air conditioning in Florida, didn't think there were any suitable models and you would need to go for the much more expensive ground-source pump.
Do you know of any air-pumps that would do the trick there?
A very common choice for a central unit would be an air source, air supply heat pump. I like the Carrier units with a scroll compressor and variable speed motor on the evaporator. Good down to high 30s F.
And a gas furnace with variable speed motor (such as Carrier MVP unit) if colder operation is needed.
For window unit, the highest SEER a/c is also a Freidrich heat pump.
These are as common as dirt on this side of the pond :-)
Thanks Alan. What sort of ratio do you get with them for energy in and out? After our friend in a post above gave a hint to look at the Duskin and Matsushita units I found this link: http://japancorp.net/article.asp?Art_ID=6383
Electric Companies Offer Jointly Developed Air Conditioning Unit
This gives an incredibly high performance ratio of 4.1/3.7 - do you get that sort of performance from the units you mention?
That ratio WAS for cooling. Alan!
From the link I gave:
This product offers the world's highest coefficient of performance, a remarkable 4.1/3.7 (cooling capacity: 160/180kW at 50/60Hz), in the field of air-cooled chiller units used for air-conditioning in buildings and factories.
Well, Dave, I'm not a HVAC engineer, but I'll go out on a limb and potentially embarrass myself by saying that just about any central a/c, chiller or heat pump manufactured today would perform equally well in this type of climate. [For those who want to explore this matter in greater detail, residential CACs and heat pumps sold in the United States are tested in accordance to the ARI 210-240-2006 performance standard and a copy of this standard can be download at http://www.ari.org/ARI/util/showdoc.aspx?doc=9]
I believe the Fujitsu 9RLQ ductless heat pump is rated at 21 SEER (seasonal energy efficiency ratio), which makes it 1.5 times more energy efficient that what is now required by law. SEER is similar to EER, a measurement of continuous operation at a steady 35C/95F, except that it better reflects relative performance over a wider range of operating temperaturs -- as one would expect to encounter over the course of the cooling season -- and takes into consideration various cycling losses. To convert a SEER rating to COP, the metric applicable to ground source systems, you divide this number by 3.793. Thus, a 13 SEER base model would have a COP of 3.43, a mid-efficiency 16 SEER unit would check in at 4.22 and an ultra high efficiency 21 SEER model would give us a COP of 5.54.
I really can't say to what extent relative humidity impacts cooling performance. I'm sure there are other members of this group better qualified to answer these types of questions and I would certainly encourage them to speak-out if they so wish. From my layman's perspective, the delta between an outdoor air temperature of 35C and an indoor temperature of 20C in cooling mode is really no different from an indoor temperature of 20C and an outdoor temperature of 5C when operating in heating mode; it's basically the same amount of "lift", just that the refrigerant is flowing in the opposite direction. Relative humidity over the condensor and evaporator would no doubt impact performance a few percentage points either way due to the effects of latent and sensible heat but, again, I wouldn't expect this to be a dominant factor in terms of overall efficiency.
I hope I answered your question (and did so correctly).
Thanks Paul - you sound pretty safe on that limb to me!
I think what is confusing me is that most of our systems in the UK are use water for hot water, not air, and are not usually used for cooling - if you do set them up to do this then you don't get any grant aid which may be available.
It seems that if you want to de-humidify too you might have to take care which air-con system you choose
Hi Dave,
Actually, conventional air conditioning systems do dehumidify and that's a big part of their job. I believe some of the newer systems in large commercial/office environments run chilled water through high mass floors and ceilings, thereby providing radiant cooling much like they would heating. I believe these systems work in tandem with an independent air handling system that provides fresh air and humidity control. The rationale behind these systems, as I understand it, is to minimize the size of the air handling system and to lower operating costs (much less energy is required to move those BTUs around via water than by air).
Those Daikin ductless system are interesting but I wonder how they prevent the water supply line that connects the outside compressor to the indoor air handler from freezing in cold weather. Also, I would expect that line to get a tad skunky over time and I'm not sure I'd want to be introducing potentially contaminated water droplets into the living space.
The number(s) you quote are correct when converting EER to COP, but in the case of SEER, I'm told the number is 3.793 -- because the testing conditions are different, SEER ratings are roughly 1.1 times higher than their equivalent EER values and this why the conversion factor is likewise higher.
In my case sizing is determined by the need to charge an electric vehicle. It uses a 100Ah 72 volt battery pack. I can't seem to figure out the minimum solar pack needed to charge it (200Ah 72 volt? or what?). I would probably use an inverter and charge thru the on-board charger rather than directly.
Well, you can have the array be 72 volt, or whatever voltage you want it to be, especially if you have an inverter that you're using. However, you want the wattage to be high enough to compensate for the consumption of the charger. There will be efficiency losses for converting from DC PV to AC with the Inverter, then AC to DC with the charger. It's much more convenient than a direct charge, however.
For a decent range on an EV, you're looking at around 12kwh in storage. At a consumption of 250wh/mile, you will get a range of 48 miles, if you drain the pack dead. (Not a good idea to do.) Ideally, you would only drain it to 50% capacity at maximum, which gives you a 24 mile range. If you want to charge that 6kwh that is consumed each day, you will need around 1.5kw of solar panels. (1.5kw X 4.5 hrs peak average = 6.75kwh/day.) Of course, your average peak solar depends on the season, where on this planet you live, etc.
Anyhow, I don't have any direct experience with EV's, I've just done research on them for a couple of years now, and my experience with PV is limited to a very small 45w setup that I use for when I go camping and little things like recharging my laptop. I have learned, however, that having a good charger will help extend battery life, as a cheap charger is virtually guaranteed to kill your battery.
shastatodd: A well insulated tank style electric water heater will produce your BTUs for less money than a demand gas unit.
This is false. I'm wondering how you came to this point of view.
Just check the EPA stickers and compare. Electric tanked is about twice as expensive as tankless gas in most places with any usage patterns. Any tankless is more efficient than any tanked heater you can buy at Lowe's or Home Despot.
We are changing from electric tanked to solar thermal backed by on-demand gas. If we had just changed to gas we'd cut our water heating in half and pay off the new tankless unit in a few years.
Also note that electric tanks heat more slowly than gas tanks or electric or gas tankless units. Also note that GHGs from coal-fired electric water heating are significantly higher than GHGs from propane-fired direct heating. Most gas tankless units approach high-80% efficiencies.
For homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters. They can be 8%–14% more energy efficient for homes that use a lot of hot water—around 86 gallons per day. You can achieve even greater energy savings of 27%–50% if you install a demand water heater at each hot water outlet.
I don't believe the savings over newer electric water heaters are quite as impressive as they are for gas. The EF of a new, well insulated electric water heat can be as high as 0.95, so standby losses for some of the better models should not exceed 5 per cent (the current minimum standard for a 50 U.S. gallon model is 0.90).
This EF value is calculated in accordance to the US DOE's "Uniform Test Method for Measuring the Energy Consumption of Water Heaters" testing procedure and is based on a designated pattern of usage over a 24-hour period (i.e., a total of 64.3 gallons of hot water/day, an inlet temperature of 58F, a nominal outlet temperature of 135F, and an ambient air temperature of 67.5). This is said to be representative of the hot water consumption of a "typical" U.S. household, although I suspect it may be somewhat high given the growing popularity of more efficient clothes washers and dishwashers, as well as reduced-flow shower heads and other water saving devices and, hopefully, behaviour changes in response to higher energy prices.
Be that as it may, according to these tests, a 50 gallon electric hot water tank that meets the minimum federal standard consumes 4,879 kWh/year. A similar size tank with an EF of 0.93 would use 4,721 kWh/year and, at the top end, one with an EF of 0.95 would be rated at 4,622 kWh/year. That puts the standby losses for each of these tanks at 488, 330 and 231 kWh/year respectively. At $0.10 per kWh, 231 kWhs would cost the consumer less than $2.00 per month, or even less if the homeowner is located in a heating dominate climate and the tank is located in a conditioned space where this waste heat would help offset a portion of the home's heating demand. Older tanks can also be wrapped with external insulating blankets to help minimize these losses.
And for anyone living in Ontario, an electric demand unit would be ill advised. The reason? Within the next two to three years, all residential consumers will have been shifted to time of use rates, so their operation during peak times (i.e., anytime after 7:00 am) will be about three times more costly than during off-peak; much better in this case to stick with a conventional water heater that is controlled by a timer so that it recharges during off-peak hours. Over time and as advanced metering costs continue to decline, I wouldn't be surprised if more jurisdictions adopt mandatory TOU in an effort to help utilities better manage their loads, reduce emissions and operating costs, and avoid/delay new capital construction.
Thanks for your response. I found your estimates and links helpful.
Regulations have improved all flavors of water heaters over the last 20 or so years in the US and Canada, so that the differences between tanked and tankless are smaller. Nevertheless:
Electric tank heaters:
* have largest greenhouse gas emissions (when coal fired)
* are the most expensive to run
* have the lowest recovery rates among water heaters
* last the shortest amount of time (~12 years)
* have the largest mass footprint and require more energy to move around
and recycle
Gas tankless heaters:
* have the lowest GHG emissions (except for nuclear-electric)
* last longer than tanked
* are cheaper to run (and can be run without a generator in
deep-standby applications)
* have infinitely fast recovery time, i.e., infinite run time
* have tiny mass footprints and can be replaced by parts, including
the heat exchanger
Additionally, tankless heaters can follow solar thermal, which is what I'm installing right now and which will provide > 60% of our water needs from the sun.
There is not a single electric tanked water heater in the US which costs less to run than any gas tankless water heater, as far as I can determine. There may be exceptions where electricity is very cheap or gas or propane are very expensive but neither of those applies to us or anywhere close.
what about the initial cost ? i looked at this in '04 (tankless ngas vs tankful ngas) and concluded that the tankless wouldn't payout in the expected life of the tankful. (just used the mandated yellow tag energy cost estimates, which does not account for peak ngas).
Great points and thank you for the links too. I'll confess I've never felt comfortable recommending the use of electric water heaters; there's something inherently wrong applying a premium fuel to such a low grade service. Natural gas, where available, would normally be my first choice, although I'm starting to think the long-term outlook for natural gas is negative and that we could be looking at rapidly escalating prices and supply issues in the not too distant future.
For those, like myself, who don't have access to natural gas our choices boil down to electric or, alternatively, propane, oil and possibly solar, either alone or in combination with one of these other three. At $1.05/litre and with an EF of 0.65, the operating costs of a standard propane water heater would be $0.228 per kWh(e) or more than twice that electric ($0.1067). A tankless unit with an EF of 0.82 would be a little more economical at $0.181 per kWh but still 1.7x more costly than electric. Solar was out due to poor orientation (east-west), a complicated roof design and severe shading. I ended up sticking with oil but, in hindsight, I wish I had opted for electric.
At this point, I'm inclined to recommend a heat pump water heater (HPWH). The EF in this case is in the order of 2.0 to 2.4, which makes it twice as efficient as a conventional water heater. As mentioned in another thread, I run my dehumidifier virtually non-stop between May and October and a Nyle HPWH which I can purchase for a little over $800.00 could perform this service and, at the same time, provide me with all the hot water I require at no additional cost. In climates where cooling demands are high, a HPWH might make even more sense.
With respect to electric demand units, there are a couple of things that bother me, but one in particular is their huge power draw. Those 80, 90 and even 120-amps can put a huge stain on a home's electrical service and, in turn, the local distribution system. You can just imagine what would happen if everyone started to replace their electric hot water tanks with one of these. From a utility point of view, a conventional water heater at 3.0 or even 4.5 kW is a whole lot kinder than a 25.0 kW demand unit, especially when placed under load control. And a HPWH at less than 1.0 kW is largely invisible.
What you do is use a timer. Ours is on from 12 noon to 7 in the evening, and we generally have a full tank of hot water in the morning. So you use that window to do dishes, laundry is strictly cold water anyway. Take your bath in the evening, it's hubris to think when you decide you need hot water it should just be there for you.
"it's hubris to think when you decide you need hot water it should just be there for you."
I'm a retired engineer, and if I felt like that I'd either take cold showers or shoot myself.
We get hot water for free from the sun most of the year, stick it in a tank (surface area goes up by x^2 while volume goes by x^3 so larger tanks are better) and supplement with a little propane once in a while, and I'll enjoy my showers whenever I want. It's easy.
Some top-notch stuff there, and it has changed my thinking, although I sometimes have trouble translating American terms into our English market, and costs and the structure are often different here anyway.
Most people hare use a combination gas boiler, with a tank.
All our meters have provision for charging at different rates at different times of the day, so if you are in a flat many of which do not allow the use of gas then overnight electric tanks are common - that is what I have.
However, I still kept the old on-demand electric water heater, which installs over the sink, and which I used to use in an old rented flat many years ago, and have always had a hankering for them - no heating water which I am not going to use, or using a bit then having gallons get cold in the piping, and contrariwise no running out on the rare occasions when I use a lot.
You are the best of all advisers, one who suggests that it is a good idea to do what I fancied doing anyway! You could make a lot of money doing that!
Seriously, that is a lot more attractive than forking out thousands on a air-heat pump driven system- a couple of those and I can switch off my tank most of the time, and only turn it on when I want to wash clothes- I m in the habit of doing that frequently, but with a bit of planning could easily manage with once week.
Do you have a relatively flat front to your home? If so, continue...
Do you have a basement, or, can you dig out at least a partial one, or, can you modify your home to have an earthen berm around N, E and W? If so, continue...
If all this is yes, it might be worth checking how much you could do a finished or unfinished basement and add a passive solar front to your home. Also, add vents to allow air to circulate through the areas. You can see the Earthships and Enertia homes for ideas. NOTE: Neither is unique in using these basic concepts. Envelopes and passive solar are both widespread and old technology. (Both do have elements that would be proprietary, I imagine.)
Before you buy the solar system, have you thought about what $20,000 can do elsewhere in your budget? What would happen if you bought a Prius, and sold your existing compact to someone who promsied to junk their SUV? What would happen if you put in a ground source heat pump? What would happen if you sold your home, and moved right next to your work? I have thought about putting in a solar system, but the price just tells me that it is really for show right now: I get better bang for buck, whether in dollar returns or decreased carbon emissions, everywhere else. My next $20k investment, after my $20k in the Prius, is the GSHP. I suggest that you look at your carbon footprint, not just in natural gas or coal used to generate electricty, but also in transportation, eating, etc. Solar is in the works for us, just not for a while.
And, if you live close enough to work, consider buying an electric scooter for less than $3k. Replacing an SUV with a scooter will far outweigh the solar panels, in your pocketbook and for the environment.
From a social perspective. investing in Canadian Hydro Developers does more good. A bit over 7 kWh# of renewable energy (much of it hydro with 100+ year life spans) per share and growing as all profits and cash flow plowed back into development of more renewable energy (no dividends).
A changing emphasis to wind (but a couple of small hydro projects in development) and a biomass facility.
# Hydro production has 30% annual variability, wind 15%.
Alan
Good points, but I drive an 8 year old Honda roughly 5k miles a year, if that. I do need to bike to work more, but can and do at times.
Heat pump might be an idea worth pursuing...although heat isn't needed much here obviously it produces AC also. I'll be busy researching every option this weekend I suppose...
And yes to...Dave? below, looks like the payback for solar water panels is even better so I'm seriously thinking about doing that at the same time. My local utility pays extra for that (I think they convert BTU's to KWH and tack on 2-3 cents extra) but for PV power they give me a 5 cent credit for every KWH I would produce-that's over and above what their retail rate is.
But then again getting rid of the heater entirely and going with instant gas hot water would be nice also. My girlfriend would appriciate the extra closet space...
While you might be doing a grid-tie solution, I'm planning on going off-grid with my PV system. For me, it's not a matter of cost, it's a matter of having electricity no matter what happens to the grid, plus it forces conservation on my part. It also means I won't have an electric power guy on my land to read my meter, worry about having a licensed electrician do everything, etc, etc. I'm just crazy like that, though. ;)
Exactly, I can't imagine not having some storage on site. The grid will go down. Even 4 or 6 100amp hour agms would be a blessing in that case. We started with the battery bank first, with inverter, and charge the batteries from the grid. Easy enough to add an alternative charging source at any time.
"I'm planning on going off-grid with my PV system."
Why not install a grid tied with battery back up system? This would allow you to bank excess summer generation for winter use. The batteries can be sized to give you hours or days of backup power.
Not grid tieing will make your system less efficient as any surplus generation will be wasted rather than sold to the grid.
Todd
I am really curious why the systems are sized so large. Two people, maybe even include some kids, don't need a lot of power at any given time -- if you use low-wattage lights and turn them off when not needed, avoid power sucks like plasma-screen tv's, dry clothes on a clothesline, and so on.
If natural gas is available, it is surely more efficient in every way to use it as a primary heat source for hot water on cloudy days, heat for the clothes dryer when the sun isn't shining, space heating when solar is insufficient, etc. Turning gas to heat to make electricity to make heat makes little sense.
On the other hand, sizing individual solar installations to be big enough to run motors and compressors and other major power drains doesn't seem to make sense to me, either -- especially when you are already tied to a grid.
Why not assemble a system that takes advantage of all sources, using the best of each.
Use the home-solar for water heat, lighting, light electrical; gas for backup heat and cooking; grid for heavy electrical.
What can you get for $10K in solar installation?
Natural gas is not available where I live. My electric service is already unreliable. I have regular short outages and a longer outage every time there is severe weather (which is more often these days). So far the longest outage was 44 hours.
I have a 360' deep well. When I lose electricity I lose water. The well is deep enough that the pump uses a lot of electricity (it uses 220V). Frozen food doesn't do well after 44 hours of outage, though I do intend to invest in a 0.5KWH DC freezer one I have PV panels up. I have a gasoline-powered generator for the longer outages now, but that's problemmatic in the long run.
The only option I see is about 4kw of panels and enough batteries to last maybe 3 days. However, before I do the PV, I'm doing solar hot water and a geothermal heat pump to replace my oil burner.
It's all going to be very expensive. However, the grid is only going to get worse. The outages will be more frequent, and it will take longer and longer for the repair crews to get out where I live. And I can't live without water (though I am investigating a DC pump...I'm just not sure there are any that can handle 360' with enough pressure to backwash my iron-removal system).
Everyone's situation is different. Most city people can rely on grid most of the time. Country and off-grid a different story, and different mix of resources.
Most people don't need much electrical power, and if you have battery backup, an unreliable grid is not so much of a problem. Lifting water 250feet takes some serious energy-- living where that is necessary obviously involves a whole different order of tradeoffs.
Seems like the poles of the spectrum are technological beauty or beauty of simplicity -- and a real-world solution involves certain compromises and certain aesthetic choices along that spectrum. Obviously, the choices will be different for everyone.
I'm still curious what kind of system you can get for $10K.
A reference I have used many times to look into grid tied systems. Not affiliated or even purchased anything from them.
http://www.mrsolar.com/page/MSOS/CTGY/ce
In Switzerland, imho, an it is very ho, what individuals can do to reduce ‘overall’ energy consumption, are, in the two unordered top positions:
1) insulate home to top standards. For the mass of apartment dwellers this means lobbying, arm twisting and paying more (transformations, etc.) facing Building Societies, large property owners, banks, etc. Not easy. Geothermal heating is a second point here.
2) reduce or eliminate meat consumption.
Now my at the mo. two top picks could be contested, and of course they are set in a business as usual scenario, etc. My point is not to prove I’m right, which would be impossible in any case, the numbers aren’t there, but to show that the first does bring financial advantages to the dweller (less spent on heating etc., even if very long term investment) while the second doesn't afford any advantages at all except socially, being pure about not eating beef filet, having success with veggie women/men, etc.
The links between drafts and icy beds and burning FF are quite direct, for the other - no. Typically, Switz. is enforcing very strict building standards and controls, rightly so, but the agri. circuit is not touched.
Difference is: upgrading or transformin housing is good biz - many will earn money. Down grading imports or meat agri. will harm importers, farmers, bison and ostrich farmers (considered green), meat producers, salt of the earth, etc. etc. so it can't be done.
Hi Noizette,
Your advice is solid and although I haven't spent a lot of time examining the linkage between energy and meat (I'm not much of a meat eater myself), I do think we can do far more to make our homes and commercial spaces more energy efficient. It's painful for me to enter a shopping mall for several reasons, but I'm especially appalled by the amount of energy consumed by their lighting and a/c systems. Light levels in most stores is excessive, to say the least, and much of it is provided by woefully inefficient halogen sources. The ubiquitous 75-watt halogen PAR38 operates at roughly 15 lumens per watt. If store owners kept their existing fixtures and simply swapped-out these bulbs (micro space heaters) for the latest generation of halogen IR lamps that produce upwards of 25 lumens per watt, they could obtain the same amount of light for about 40 per cent less energy. Better yet, replace those fixtures with new ceramic metal halide lighting (e.g., Philips MasterColour Elite) and you would get similar or arguably better light and slash power and a/c loads by as much as 85 per cent. This is just one example of what we can do right now and at very nominal cost; the potential energy savings are enormous and when you look at the numbers, the financial benefits are resoundingly positive.
Another case in point. Several years ago, I replaced a 455-watt metal halide fixture in a retail store that ran 24-hours a day as a security light with a two-tube, low ballast factor, T8 fluorescent that operates at 55-watts (as a night light, the replacement was more than adequate). The change-out of this one fixture saves enough electricity to power my home's heat pump for the entire year!
With respect to geothermal heating, I'll simply add that we shouldn't overlook their air-source brothern. DaveMart and I have discussed this at great length in other threads so I won't go into the details here; suffice to say they're often much less expensive and can be installed with fewer complications and restrictions and in many cases will do just as good a job.
Cheers,
Paul
"Air source" heat pumps are very common in Asia, where in the most populated areas, the temperature rarely drops below freezing but might be in the 32-55 degree range. This could be appropriate for California, Georgia, etc.
They work as both air conditioners and heat pumps. Try the Duskin brand for example. Matsushita also makes them.
Paul, you know me, I nearly mentioned air heat pumps, but with the high humidity and need for air conditioning in Florida, didn't think there were any suitable models and you would need to go for the much more expensive ground-source pump.
Do you know of any air-pumps that would do the trick there?
A very common choice for a central unit would be an air source, air supply heat pump. I like the Carrier units with a scroll compressor and variable speed motor on the evaporator. Good down to high 30s F.
And a gas furnace with variable speed motor (such as Carrier MVP unit) if colder operation is needed.
For window unit, the highest SEER a/c is also a Freidrich heat pump.
These are as common as dirt on this side of the pond :-)
Alan
Thanks Alan. What sort of ratio do you get with them for energy in and out? After our friend in a post above gave a hint to look at the Duskin and Matsushita units I found this link:
http://japancorp.net/article.asp?Art_ID=6383
Electric Companies Offer Jointly Developed Air Conditioning Unit
This gives an incredibly high performance ratio of 4.1/3.7 - do you get that sort of performance from the units you mention?
Heating is a byproduct and efficiency there is of minor importance. The real key is summer air conditioning and especially humidity removal.
I will have to look at the ARI stats for current models.
Best Hopes from a sunny 25 C New Orleans,
Alan
That ratio WAS for cooling. Alan!
From the link I gave:
Pretty good, huh?
Dunno about heating - they don't specify there.
Well, Dave, I'm not a HVAC engineer, but I'll go out on a limb and potentially embarrass myself by saying that just about any central a/c, chiller or heat pump manufactured today would perform equally well in this type of climate. [For those who want to explore this matter in greater detail, residential CACs and heat pumps sold in the United States are tested in accordance to the ARI 210-240-2006 performance standard and a copy of this standard can be download at http://www.ari.org/ARI/util/showdoc.aspx?doc=9]
I believe the Fujitsu 9RLQ ductless heat pump is rated at 21 SEER (seasonal energy efficiency ratio), which makes it 1.5 times more energy efficient that what is now required by law. SEER is similar to EER, a measurement of continuous operation at a steady 35C/95F, except that it better reflects relative performance over a wider range of operating temperaturs -- as one would expect to encounter over the course of the cooling season -- and takes into consideration various cycling losses. To convert a SEER rating to COP, the metric applicable to ground source systems, you divide this number by 3.793. Thus, a 13 SEER base model would have a COP of 3.43, a mid-efficiency 16 SEER unit would check in at 4.22 and an ultra high efficiency 21 SEER model would give us a COP of 5.54.
I really can't say to what extent relative humidity impacts cooling performance. I'm sure there are other members of this group better qualified to answer these types of questions and I would certainly encourage them to speak-out if they so wish. From my layman's perspective, the delta between an outdoor air temperature of 35C and an indoor temperature of 20C in cooling mode is really no different from an indoor temperature of 20C and an outdoor temperature of 5C when operating in heating mode; it's basically the same amount of "lift", just that the refrigerant is flowing in the opposite direction. Relative humidity over the condensor and evaporator would no doubt impact performance a few percentage points either way due to the effects of latent and sensible heat but, again, I wouldn't expect this to be a dominant factor in terms of overall efficiency.
I hope I answered your question (and did so correctly).
Cheers,
Paul
Thanks Paul - you sound pretty safe on that limb to me!
I think what is confusing me is that most of our systems in the UK are use water for hot water, not air, and are not usually used for cooling - if you do set them up to do this then you don't get any grant aid which may be available.
It seems that if you want to de-humidify too you might have to take care which air-con system you choose:
http://www.daikineurope.com/products/for_your_home/ururusarara/default.j...
It seems that if you want to de-humidify too you might have to take care which air-con system you choose
Hi Dave,
Actually, conventional air conditioning systems do dehumidify and that's a big part of their job. I believe some of the newer systems in large commercial/office environments run chilled water through high mass floors and ceilings, thereby providing radiant cooling much like they would heating. I believe these systems work in tandem with an independent air handling system that provides fresh air and humidity control. The rationale behind these systems, as I understand it, is to minimize the size of the air handling system and to lower operating costs (much less energy is required to move those BTUs around via water than by air).
Those Daikin ductless system are interesting but I wonder how they prevent the water supply line that connects the outside compressor to the indoor air handler from freezing in cold weather. Also, I would expect that line to get a tad skunky over time and I'm not sure I'd want to be introducing potentially contaminated water droplets into the living space.
Cheers,
Paul
Divide by 3.793
I believe that it is 3.412 or 3.413 (depending on which way one rounds).
Alan
Hi Alan,
The number(s) you quote are correct when converting EER to COP, but in the case of SEER, I'm told the number is 3.793 -- because the testing conditions are different, SEER ratings are roughly 1.1 times higher than their equivalent EER values and this why the conversion factor is likewise higher.
Cheers,
Paul
In my case sizing is determined by the need to charge an electric vehicle. It uses a 100Ah 72 volt battery pack. I can't seem to figure out the minimum solar pack needed to charge it (200Ah 72 volt? or what?). I would probably use an inverter and charge thru the on-board charger rather than directly.
Well, you can have the array be 72 volt, or whatever voltage you want it to be, especially if you have an inverter that you're using. However, you want the wattage to be high enough to compensate for the consumption of the charger. There will be efficiency losses for converting from DC PV to AC with the Inverter, then AC to DC with the charger. It's much more convenient than a direct charge, however.
For a decent range on an EV, you're looking at around 12kwh in storage. At a consumption of 250wh/mile, you will get a range of 48 miles, if you drain the pack dead. (Not a good idea to do.) Ideally, you would only drain it to 50% capacity at maximum, which gives you a 24 mile range. If you want to charge that 6kwh that is consumed each day, you will need around 1.5kw of solar panels. (1.5kw X 4.5 hrs peak average = 6.75kwh/day.) Of course, your average peak solar depends on the season, where on this planet you live, etc.
Anyhow, I don't have any direct experience with EV's, I've just done research on them for a couple of years now, and my experience with PV is limited to a very small 45w setup that I use for when I go camping and little things like recharging my laptop. I have learned, however, that having a good charger will help extend battery life, as a cheap charger is virtually guaranteed to kill your battery.
"But then again getting rid of the heater entirely and going with instant gas hot water would be nice also."
A well insulated tank style electric water heater will produce your BTUs for less money than a demand gas unit.
Todd
That depends upon the rates (and pattern of use, some people use hot water once or twice a day). In most places, not true,
Alan
shastatodd: A well insulated tank style electric water heater will produce your BTUs for less money than a demand gas unit.
This is false. I'm wondering how you came to this point of view.
Just check the EPA stickers and compare. Electric tanked is about twice as expensive as tankless gas in most places with any usage patterns. Any tankless is more efficient than any tanked heater you can buy at Lowe's or Home Despot.
We are changing from electric tanked to solar thermal backed by on-demand gas. If we had just changed to gas we'd cut our water heating in half and pay off the new tankless unit in a few years.
Also note that electric tanks heat more slowly than gas tanks or electric or gas tankless units. Also note that GHGs from coal-fired electric water heating are significantly higher than GHGs from propane-fired direct heating. Most gas tankless units approach high-80% efficiencies.
For homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters. They can be 8%–14% more energy efficient for homes that use a lot of hot water—around 86 gallons per day. You can achieve even greater energy savings of 27%–50% if you install a demand water heater at each hot water outlet.
http://www.eere.energy.gov/consumer/your_home/water_heating/index.cfm/my...
Hi NR,
I don't believe the savings over newer electric water heaters are quite as impressive as they are for gas. The EF of a new, well insulated electric water heat can be as high as 0.95, so standby losses for some of the better models should not exceed 5 per cent (the current minimum standard for a 50 U.S. gallon model is 0.90).
This EF value is calculated in accordance to the US DOE's "Uniform Test Method for Measuring the Energy Consumption of Water Heaters" testing procedure and is based on a designated pattern of usage over a 24-hour period (i.e., a total of 64.3 gallons of hot water/day, an inlet temperature of 58F, a nominal outlet temperature of 135F, and an ambient air temperature of 67.5). This is said to be representative of the hot water consumption of a "typical" U.S. household, although I suspect it may be somewhat high given the growing popularity of more efficient clothes washers and dishwashers, as well as reduced-flow shower heads and other water saving devices and, hopefully, behaviour changes in response to higher energy prices.
Be that as it may, according to these tests, a 50 gallon electric hot water tank that meets the minimum federal standard consumes 4,879 kWh/year. A similar size tank with an EF of 0.93 would use 4,721 kWh/year and, at the top end, one with an EF of 0.95 would be rated at 4,622 kWh/year. That puts the standby losses for each of these tanks at 488, 330 and 231 kWh/year respectively. At $0.10 per kWh, 231 kWhs would cost the consumer less than $2.00 per month, or even less if the homeowner is located in a heating dominate climate and the tank is located in a conditioned space where this waste heat would help offset a portion of the home's heating demand. Older tanks can also be wrapped with external insulating blankets to help minimize these losses.
And for anyone living in Ontario, an electric demand unit would be ill advised. The reason? Within the next two to three years, all residential consumers will have been shifted to time of use rates, so their operation during peak times (i.e., anytime after 7:00 am) will be about three times more costly than during off-peak; much better in this case to stick with a conventional water heater that is controlled by a timer so that it recharges during off-peak hours. Over time and as advanced metering costs continue to decline, I wouldn't be surprised if more jurisdictions adopt mandatory TOU in an effort to help utilities better manage their loads, reduce emissions and operating costs, and avoid/delay new capital construction.
Cheers,
Paul
Hi Paul,
Thanks for your response. I found your estimates and links helpful.
Regulations have improved all flavors of water heaters over the last 20 or so years in the US and Canada, so that the differences between tanked and tankless are smaller. Nevertheless:
Electric tank heaters:
* have largest greenhouse gas emissions (when coal fired)
* are the most expensive to run
* have the lowest recovery rates among water heaters
* last the shortest amount of time (~12 years)
* have the largest mass footprint and require more energy to move around
and recycle
Gas tankless heaters:
* have the lowest GHG emissions (except for nuclear-electric)
* last longer than tanked
* are cheaper to run (and can be run without a generator in
deep-standby applications)
* have infinitely fast recovery time, i.e., infinite run time
* have tiny mass footprints and can be replaced by parts, including
the heat exchanger
Additionally, tankless heaters can follow solar thermal, which is what I'm installing right now and which will provide > 60% of our water needs from the sun.
There is not a single electric tanked water heater in the US which costs less to run than any gas tankless water heater, as far as I can determine. There may be exceptions where electricity is very cheap or gas or propane are very expensive but neither of those applies to us or anywhere close.
Some more links:
Consumers' Directory of Certified Efficiency Ratings for Water Heating Equipment: http://www.gamapower.org/water.php
http://www.aceee.org/consumerguide/waterheating.htm
http://www.eere.energy.gov/buildings/info/homes/choosingwater.html
And it's late and I think nobody will see this :-0
Best regards,
NR
what about the initial cost ? i looked at this in '04 (tankless ngas vs tankful ngas) and concluded that the tankless wouldn't payout in the expected life of the tankful. (just used the mandated yellow tag energy cost estimates, which does not account for peak ngas).
Hi NR,
Great points and thank you for the links too. I'll confess I've never felt comfortable recommending the use of electric water heaters; there's something inherently wrong applying a premium fuel to such a low grade service. Natural gas, where available, would normally be my first choice, although I'm starting to think the long-term outlook for natural gas is negative and that we could be looking at rapidly escalating prices and supply issues in the not too distant future.
For those, like myself, who don't have access to natural gas our choices boil down to electric or, alternatively, propane, oil and possibly solar, either alone or in combination with one of these other three. At $1.05/litre and with an EF of 0.65, the operating costs of a standard propane water heater would be $0.228 per kWh(e) or more than twice that electric ($0.1067). A tankless unit with an EF of 0.82 would be a little more economical at $0.181 per kWh but still 1.7x more costly than electric. Solar was out due to poor orientation (east-west), a complicated roof design and severe shading. I ended up sticking with oil but, in hindsight, I wish I had opted for electric.
At this point, I'm inclined to recommend a heat pump water heater (HPWH). The EF in this case is in the order of 2.0 to 2.4, which makes it twice as efficient as a conventional water heater. As mentioned in another thread, I run my dehumidifier virtually non-stop between May and October and a Nyle HPWH which I can purchase for a little over $800.00 could perform this service and, at the same time, provide me with all the hot water I require at no additional cost. In climates where cooling demands are high, a HPWH might make even more sense.
With respect to electric demand units, there are a couple of things that bother me, but one in particular is their huge power draw. Those 80, 90 and even 120-amps can put a huge stain on a home's electrical service and, in turn, the local distribution system. You can just imagine what would happen if everyone started to replace their electric hot water tanks with one of these. From a utility point of view, a conventional water heater at 3.0 or even 4.5 kW is a whole lot kinder than a 25.0 kW demand unit, especially when placed under load control. And a HPWH at less than 1.0 kW is largely invisible.
Cheers,
Paul
What you do is use a timer. Ours is on from 12 noon to 7 in the evening, and we generally have a full tank of hot water in the morning. So you use that window to do dishes, laundry is strictly cold water anyway. Take your bath in the evening, it's hubris to think when you decide you need hot water it should just be there for you.
"it's hubris to think when you decide you need hot water it should just be there for you."
I'm a retired engineer, and if I felt like that I'd either take cold showers or shoot myself.
We get hot water for free from the sun most of the year, stick it in a tank (surface area goes up by x^2 while volume goes by x^3 so larger tanks are better) and supplement with a little propane once in a while, and I'll enjoy my showers whenever I want. It's easy.
Thanks, Nervous!
Some top-notch stuff there, and it has changed my thinking, although I sometimes have trouble translating American terms into our English market, and costs and the structure are often different here anyway.
Most people hare use a combination gas boiler, with a tank.
All our meters have provision for charging at different rates at different times of the day, so if you are in a flat many of which do not allow the use of gas then overnight electric tanks are common - that is what I have.
However, I still kept the old on-demand electric water heater, which installs over the sink, and which I used to use in an old rented flat many years ago, and have always had a hankering for them - no heating water which I am not going to use, or using a bit then having gallons get cold in the piping, and contrariwise no running out on the rare occasions when I use a lot.
You are the best of all advisers, one who suggests that it is a good idea to do what I fancied doing anyway! You could make a lot of money doing that!
Seriously, that is a lot more attractive than forking out thousands on a air-heat pump driven system- a couple of those and I can switch off my tank most of the time, and only turn it on when I want to wash clothes- I m in the habit of doing that frequently, but with a bit of planning could easily manage with once week.
Is your home South facing? If so, continue...
Do you have a relatively flat front to your home? If so, continue...
Do you have a basement, or, can you dig out at least a partial one, or, can you modify your home to have an earthen berm around N, E and W? If so, continue...
If all this is yes, it might be worth checking how much you could do a finished or unfinished basement and add a passive solar front to your home. Also, add vents to allow air to circulate through the areas. You can see the Earthships and Enertia homes for ideas. NOTE: Neither is unique in using these basic concepts. Envelopes and passive solar are both widespread and old technology. (Both do have elements that would be proprietary, I imagine.)
www.enertia.com
A third, and perhaps simpler, cheaper and easier option would be to add a hay bale shell around your existing home, with the passive solar front. http://www.strawbale.com/using-straw-bales-to-insulate-a-house#more-321
A successful conversion on any of these fronts would eliminate all or most of your need for heating and cooling.
Cheers