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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.