portland independent media center  
images audio video
newswire article creative global

energy & nuclear | sustainability | technology

Free Air-Conditioning from the Earth!

Cool Tubes are long tubes using drainage tile or other material that is buried in the ground with the intake end of the tube outside the home and the exhaust end inside the house. The idea is that the earth will cool the air passing through tube providing a cheap, clean, and renewable source of cool air.
The government's website claims either that this concept doesn't work or there isn't enough data about it to draw a conclusion.

Does anybody have any first-hand knowledge about Cool Tubes they would like to pass along?


Gov site :

add a comment on this article

Ancient Cool Tubes 17.Jan.2005 13:22

Burro Bob

Wupatki National Monument is located 35 mi. North of Flagstaff, AZ. Here, there is a large rectangular structure believed to be the northernmost "ball court" associated with the Hohokam culture. Near it, a "blowhole" expels cool air from underground volcanic fissures. Archaeologists have speculated that it may have provided a type of prehistoric air conditioning.

I have visted this area in the 1980's. While the outside temperature was very warm, a constant rush of cool air came up from the chest-high blowhole to cool off a friend and myself.

This is further evidence that the corporations and government do not want us to have anything that is low-cost or free.

not first hand 17.Jan.2005 21:24


First off, one thing strikes me as a bit odd about the government assessment. It says the tubing material doesn't matter. Nonsense. A nonconductive material would clearly have a very low energy exchange rate which would clearly render such tubes less effective.

Which brings me to the next point--these tubes are not going to be useful in every situation. In areas where the soil is very dry, the conductivity is lower, and thus the dirt surrounding the tubes would serve as an insulator. Wet soil would be the way to go.

If the tubes were spiked or finned, similar in concept to a cpu cooling system, heat could be pulled from or pushed to a larger area of soil which would go part of the way towards compensating for lower-conductivity dirt situations.

The tubing humidity would seem to be a bit of an issue for air quality (don't want mold spores in the air that's for sure). If the tubes were angled to puddle the water at one end, perhaps a drain could be set up, or better yet a small pump. Even so, a periodic decontamination would seem prudent UNLESS you used the tubes as a completely closed system which started out with zero humidity. But then you'd be talking about a very expensive portion in-house to capitalize upon the exchange.

In short, problems exist, and it probably isn't worth thinking about as a retro-fit unless energy prices spike or you're in a unique situation, such as by a flowing body of water which provides a large temperature differential.

the system at People's Food Co-op works great 18.Jan.2005 00:07


Since the remodeling of the store, People's Food Co-op has used a heat pump system (air is pumped from deep underground) for heating and cooling. I've been to the store on very hot days that the in-store temperature was quite cool. Some info on the green features at People's here:

The website for People's (though it has not been functioning today):

From the US Dept. of Energy Web page linked in the original post:
"...but information on the practical application of the concept is limited."
Heat pumps are a proven technology. This article was probably written by a bureaucrat who was put in the position to look out for corporate interests, in this case the fuel and power companies that make money by selling you electricity. If I had time to research it, I could itemize many people at the Dept. of Energy who went directly from an industry such as coal or oil to their current position at the DoE. I would hesitate to believe anything I see on a US gov't website.

From an Eco house building student 18.Jan.2005 00:48


I am very interested in this eco developer , I went out to Fairfield Iowa to look over one of his developments. Mind you Fairfield Iowa is a nasty place in the summer very hot. He had worked out a natural system for passive cooling using pipes in the ground and a natural thermal siphon. I saw them put it in, many people had come to study what he was doing. This is his web site, i have not kept up with his doings. But i know he would know.


The Commonwealth Building 18.Jan.2005 12:26


The Commonwealth Building in downtown Portland installed a geo-thermal heat pump about 15 years ago. It is amazing that this is not done more often.

add a comment on this article