Earth tubes

[DYork]

Thoughts? Is this viable if one can overcome the humidity/condesation build-up?
(the guy 'appears' to have something to sell, but I'm just concerned with the concept. No freon and no hi wattage compressor.)
There are many sites that explain this, but this seems to be one with better illustrations. I'm not too interested in the heat aspect of it, as we have very mild winters in E Texas.

http://mb-soft.com/solar/intake.html

[rreidnauer]

Ha, we did the same thing with our basement before we had A/C. (though, we quickly ran out of cool air with such a small volume of air and had the humidity problems too) Much better would be a geothermal via water pumped up to a heat exchanger, but even this would be very inefficient compared to freon.

Not sure why propane isn't used as a refrigerent though. It can't burn in the 100% propane enclosed enviroment, and any leaks that (rarely) develop are typically very slow and would disapate into the atmosphere quickly. Finally, there really isn't all that much volume in a cooling system to pose a large threat anyhow. I guess it's simply not efficient enough.

[dbtoo]

My refrigerator has a propane motor, but not sure what the coolant is. I doubt that's what you were refering to.

[WillandHelen]

seems like a grea idea. This sounds like its worth a try. I think ductile iron or copper would work much better than pvc, but probably cost alot more.

[DYork]

Propane is the odds on favorite to replace HFC based refigerants once R22 is completely banned in home A/C and refrigerators, with ammonia to be used more and more in the big chillers.
One of the reasons propane hasn't been used in the past more often is because of the smell they add to it. Even a tiny leak will smell strongly in a semi-closed room. I'm not sure what the psi in one of these units would need to be tho. That's one of the drawbacks to R-134. Higher pressures.
btw, if you don't already know it, a good bit of the bootlegged R12 single use containers that come from south of the border is actually propane. They just slap an r12 label on it and sell it as such.

I would love to get completely away from anything that requires a compressor, as that is where the largest % of your monthly cost comes from. That includes the heat pumps many companies use in the geothermal installations. The payback takes many years to recoup, and that is especially true at today's energy prices.

I believe the condensation could be dealt with, with the use of a collection sump with a hnd picher pump, at the lowest point of the pipe maze, or even by installing a desicant wheel in the return line just before the line reaches the home. Perhaps a dehumidifier in the home. I do have to wonder tho, how long it would take for the earth surrounding the air flow lines to become too saturated with heat to make for good heat transfer in the deep south. The yr round ground temp at 4' depth is only in the 70 degree range in East Texas. If the water table were very near the surface, perhaps running the tube down in the water sand would help. It would seem counter productive to build large overhangs to keep rain off the outside of the log walls, only to have high humidity levels inside the home. Mildew city!! I may try this setup in a stick built shop/garage just for the heck of it tho.

WillandHelen:
I too have problems with the pvc part of this. A poor conductor of heat, especially if using schedule 80 which has a higher crush rate. But, 4" aluminum irrigation pipe is quite expensive, even used pipe. Alum degrades fairly quickly in the ground too, thru oxidation, and from the inside, if there is any moisture present.

[dee3724]

I ran across a booklet a while back entitled "Passive Annual Heat Storage" that addresses many of the issues. Unfortunately I am not sure where it is at the moment (storage I think). However, it is very informative and discusses the condensation as well as sizing the earth tubes, use of PVC and also placing the PVC pipe to prevent "nosebleeds" from developing where you don't want them to. Also, the basis for their system is what is termed a "camels nose" effect. The outgoing air (at a higher temp) is sent through the PVC and a purposefull nosebleed is formed with the incoming PVC pipe. The warmer air warms the earth around the exit tube and consequently warms the incoming air (efficient too).. Anyway, I hope this helps.

[DYork]

"nosebleeds"?
Unsure of what that means in this context.

[dee3724]

OOPS! Sorry about that. A nosebleed is (I'm assuming it was first used because of the camels nose analogy) a thermal 'leak' if you will. Usually its not something you want but at the inlet and outlet it is useful as a heat exchanger in a way. The tubes are set closer together to cause this 'nosebleed' between the tubes to pre-warm incoming air and extract some of the heat out of the outgoing air. I hope this helps.