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Can I make a chiller using cold outdoor weather instead of electricity?

my assumption was that it would, to a great degree, depend on the composition of the soil, or whatever material contained the coil. my thought was to suspend the coil in the hole, like you might rebar in a footing, keeping as much space between the coils as you could within the allowed space and then pour concrete over it to protect it.
 
My guess - but the concrete (thermal mass) may not dissipate heat as well as plain old earth. I thing it will hold heat - like when you heat a concrete slab or 2nd story floor.
I was thinking:
4' x 20'? trench maybe 6' deep. Spread out a coil of plastic well pipe. cover with hard board insulation (insulate from above, not below) and bury it.
 
snowmaker;160708 said:
My guess - but the concrete (thermal mass) may not dissipate heat as well as plain old earth. I thing it will hold heat - like when you heat a concrete slab or 2nd story floor.
I found a table that shows the thermal conductivity of various materials. Concrete actually conducts heat a little bit better than "earth, dry", but it's hard to say whether either one is a really bad conductor of heat, or a really bad insulator. The truth is, without knowing the equations and running the numbers (like a real engineer could) I can't say how well such a system would work (despite the fact that I already said "it won't work"). Heat will leak through the PVC, and into the earth at some rate, call it RL (loss). Your tank will produce heat at another rate, call it RG (gain). After the dirt warms up to a stable temperature, if RL is > RG, then it will work great. RL increases as the length of the buried pipe increases, so if you buried enough pipe, it certainly would work (assuming the sun doesn't keep the dirt warmer than your tank water). I'm guessing that you would need to bury so much pipe that it wouldn't be practical, but again, I'm guessing. Maybe I'll look up the equations and do this right some time, just to make sure I'm not giving bad advice.

Or you could forget the math and just try it. An easy way would be to tap into an existing sprinkler system (long network of buried pipes) and pump water from a tank with a heater in it (constantly running) through the pipes. Eventually the temp will stabilize, and you'll know how much heat that system can continuously dissipate.
 
CaptFish;160717 said:
I don't think you want the hard board insulation, it may hold the heat in. I would cover it with good old grass.

Aye, but you do...:smile:
We're talking 6' down. Put grass or whatever you want up top. The insulation will keep the plumbing insulated FROM ABOVE, where the temp varies seasonally. Insulation only goes over plumbing, not under.

If you're serious Noah, Best to find a reputable geo-thermal guy (or gal).

A guy up here has 3, 1000g concrete septic tanks buried under his garage. They're accessible, and have stainless heat exchangers in them and are used to aid heating in winter and cooling in summer. (fairly big house) He wanted to do something geothermal, but couldn't afford 3, 300'+ drilled wells (around $20k).

I do not believe "testing" through a sprinkler system will tell you anything. Those are plumbed just below the surface where ambient temp varies. Below 4' or 5' temp should be constant 50 - 55ish. Asking / hiring the engineer is the best advice here yet.
 
absolutely serious. not in my current living situation though. we plan to buy another house within the next five years, so maybe i have the time to figure out all the engineering details myself.
 
If 20K was close to the total cost and he would not have needed traditional heat and air, that would not be bad for a house of about 3,000 sq ft. It cost us over 6,000 to replace one of our 3 units two years ago and the cost to run them in the summer and winter is high (somewhere between $300 and $700 - this winter but not usually that high - a month).
 
The $20k is JUST for the well truck to come and go, leaving 3, 300+' bores in your ground.

Another interesting topic - turnkey PV electricity system - this guy in MA has a great system, and I believe the $20k system was partially paid for with government incentives of over $12k.

The overview graphs of the guys system in real time and historic.
Potvin

The "Loaded Question" regarding cost:
Gross 21434.00
Net with all credits Fed State etc 8852.00
Annual Income from system, Minimum 1200.00 Maximum 2400.00 a year they auction your generated power to Utilities this is for 10 years so 12k to 24k back in our pockets over that time frame.

Electricity produced 4100kwh a year at .18 cents is 738.00 a year.
 

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