One day when searching I ran across this site http://mb-soft.com/solar/saving.html. The author claims there are many of these systems in existence but he fails to provide even one link to one of these working systems.
Any ways here is my concept. Obviously you would need to use several of these pipe loops of equal length to get any noticeable effect. I had always thought that the 4 inch drain pipes would be the most cost effective option to use. It would be pretty easy to set up some sort of 12v fan connected directly to a solar panel to run this.
That said, 6" solid drain pipe (the thin wall two-layer stuff) is probably the cheapest right now. 4" is not enough, even for a tiny house. Earthships use steel culverts of a fairly large size.
You need 10' or more between pipes as you will over-heat the surrounding earth and the system won't work as well after a few years. Ground loop heat pumps have the same problem when people go cheap on the ground loops.
R Scott wrote:I have a friend that put a system in. Two 4" pipes running slightly down contour in the same trench from his house with the intake probably 100' total run. 800 sq ft straw bale house with sleeping loft. Two computer fans running from the solar system. It feels good standing in front of the fans, but no real difference in the whole house. He figured what it would take to upsize to something that would work and then.... bought a Honda generator and super-efficient window AC. And he is a guy that rides his horse to the store to avoid using gas. Comfort and economics won out that time.
Great to hear that some one has at least started to experiment with this. I have some questions for you.
Was he recirculating the air in the house through the system or was he drawing from outside air?
What would increasing the cfm of the fans do? I guess my question is did he just need more cfm running through the pipes or did he need more CFM and more pipes in the ground?
Obviously recirculating air in the house would be more efficient. It would also help with lowering the humidity.
There are 2 variables that need to be figured out length of loop and the amount air that can be cooled through that loop.
I was thinking something along the lines of 250-500ft loops. that would run about 100-200 dollars per loop. if you figure the drain pipe runs about $4 per ten foot length.
You would probably need from 5-10 loops to really have any real cooling.
A system like this may also be useful to keep a greenhouse from freezing on cold nights.
Anyways here is another source of information:
They use it for cooling a greenhouse, and then storing the heat to warm the greenhouse in the winter. If you could do a similar thing with the pipes under the house, and enough thermal mass, you can heat your house with the same system.