Quote:
Originally Posted by thowell2695
I have a 2 1/2 ton AC Heat pump that I want to modify. I have a Cistern that is 10Ft deep by 10 ft wide by 20 ft long full of water.
|
FordGuy is right, if your cistern is full, and you also have 125,100 pounds of water.
Depending on the heat loss of your house (you really need to do a heat loss analysis before you go any farther) ... and just for just for arithmetic purposes:
1 BTU will raise one pound of water 1 degree F.
So, if your house needed 60,000 BTU/hour (* pulling a number out of thin air *) to keep it from getting colder, and your night was 12 hours long, your house heat load could drop the cistern temp by maybe six degrees-ish in one night.
So you can see that it might not take so many nights before you would have a 125,000 pound chunk of ice buried in your yard.
The mitigating factor is that the surrounding soil will slowly give up it's heat to the cistern... and I'm afraid I don't have the math to figure out how fast the rate of heat migration from the surrounding soil would be.
BUT, for a little perspective...
A rule of thumb (a very fallible rule) is that a 250 foot bore hole with a water loop circulating through it could yield 12,000 BTU per hour. Now that is considering that the bore hole is acting like a cylinder 250 feet long, and has a diameter of maybe > 16 feet. So you see, that is a big bunch of dirt, and to keep your house warm, you would need => 5 of these bore holes.
So that's 5 times "a very big bunch of dirt".
About 251328 cubic feet, or 30,159,360 pounds.
Does this give you any perspective?
I did a fairly detailed study of this kind of thing in the
Homemade Heat Pump Manifesto thread.
I think you would find it very interesting.
Best,
-AC_Hacker