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Bcro thanks for the suggestion. I could not find that model you listed. How much energy do they use? I see Seer ratings but I don't know how that translates to amps or Watts?
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I just saw the show on Discovery Channel building Off the Grid. This guy dug big Trench around his place set up ducting in the trench and had air being sucked out through the floor pumped through the tubing in the cold ground back into his place for AC. I wonder how cold it actually is.? Would this work in Florida?Comment
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When I entered Mitsubishi ACDC12C in my internet search, it came right up. It claims an AC line SEER
of 22, already way better than the crowd. If I put in a link, it will get caught in moderation. Also on Utube.
They say it will run on 3 panels in the 300W class, I think around 110VDC. It runs better on 6 panels. I
do not know your particulars but you can look it up and decide. Bruce RoeComment
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Depends on a lot of factors, primarily on ground temp. and soil characteristics. Usually a poor idea for a lot of reasons. Not too many HVAC engineers use such methods for their own homes. Does that tell you anything ? It won't work well in most any location unless carefully designed and probably for larger than household applications.Comment
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I live in the tropics so the ground is not cold but there is a deep creek behind the house and the air is cooler down the bottom of the creek, I did think about putting in a pipe and fan to draw the cool air up.
But being off grid generally means you are a power saver/miser or very rich, so the gain from what little cool air I would get was not worth the sacrifice of power.
I have seen and read about quite a few off grid homes, they are portrayed as being the best thing since sliced bread, but you dont very often see follow ups in 5 years to see if their batteries are still ok, or how much generator run time they need to live the life they want to.
My house is just as unbearable during the night when it is monsoon season so having an A/C unit that only runs during the day is not worth my while.
I suppose what Im trying to say is do a lot of research and consider all factors, not just sales hype and what you want to hear.
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Running anything substantial off grid is not cheap. The batteries, surge capable inverter, and
much larger solar array with supports and controller are not cheap, and much larger, to deal
with the gross inefficiency of the extra components. Baby sitting a battery bank for a lifetime
with regular replacements is not something I would care to take on. Bruce Roe
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For those not in the know, I'd suggest being careful about comparing A/C or heat pumps on the basis of something called "SEER" alone. Big SEER's are inviting but can be deceptive. That "SEER" is a slippery concept and number because it's based on "seasonal" conditions. One question is : Whose season ? A second question is : Whose use pattern ? Notice that the more quantifiable "EER" for the ACDC12C is a more realistic and thermodynamically defensible 12.5 = (COP of 3.7)*(3.412 BTU/Wh).
Since any standards for calculating that number ("SEER"), such as they may exist, seem to be, by necessity/definition, loosely defined and by choice it seems more loosely enforced, if at all, and also, as an example, since "seasonal" efficiency in a cold climate will be different from "seasonal" efficiency in a warm climate, and in any case more a f(location climate) than a hard number, I'd ignore the "SEER" B.S. altogether and go by "EER" as a comparison.
To my opinion only, that SEER crap was conjured up by marketers as little more than yet another way to muddy the waters and separate folks from their money.
Better yet is to go by the COP of a device which is the ratio of the energy sought in either cooling (refrigeration), or heating (a heat pump) to the energy that's input to achieve the desired result.
While "SEER" may fit that definition in the sense that my needs may be met with more or less energy input than someone else's needs, the less than precise way the term "SEER" is defined makes it useless for much of anything beyond deception. I might get an SEER of, say, 30 out of a device because of my climate and use pattern. Some other user, even in the same climate, may not be able to do much better than a 15 or so.
Use the COP for comparison when acquiring, and use the device wisely. Forget the "SEER" crap.Comment
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OP: As those who have done it without the benefit of experience have learned - usually it seems more often than not the hard way, off grid lifestyles are expensive in terms of $$ costs and lifestyle adjustments. Living on an acre with no utilities to it will put you in a box. Either spend more than your ignorance led you to believe or adjust your lifestyle and expectations, or some mix of the two.Comment
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I am in agreement, the problem is getting every units COP to use in comparisons. Bruce RoeOriginally posted by J.P.M.Comment
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Yes it is, as listed on my ENERGY UNITS sheet awhile back. For the record the heat pump
I mentioned is EER/COP of 12.5/3.66 for cooling and a 3.42 COP for heating. If you can find
those specs on any lower tech unit, I would bet this one is much superior, before we even
start considering losses in things like charge controllers, batteries, and inverters. Bruce RoeComment
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Those and other things like fans or pumps, coil heaters for frost prevention, etc. etc. are what I learned to call parasitic losses. They will always be part of any operating system. The difference in the COP for refrigeration (3.66) vs. the COP when the unit is in heat pump mode (3.42) is inherent in the thermodynamics and is, at least as far as that science is concerned, separate from losses from supporting/ancillary equipment. The 3.66 COP for cooling may be a bit higher than some other units on the market, but not remarkably so. I've got a 13 yr. old 5 ton A/C unit that has a measured COP of ~ 3.2. Usually, but not always and not inherently guaranteed, the larger the unit, the higher the COP. A lot of it has to do with the working fluid and vapor pressure-temp. relations. See P-V and T-S diagrams from thermodynamic or HVAC texts. There's a lot more to consider with respect to safe, serviceable, reliable and economical refrigeration/heat pump systems design than COP alone. Most operate a long way from Carnot efficiency for a lot of practical reasons.
At the end of the day, the COP (and EER - and note, not SEER) is a much more reliable number to hang a hat on. It'll be subject to much less B.S. manipulation.Comment
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