I live in Tucson, Arizona and it gets hot in the summer. I was thinking about using earth air tunnels to cool a green house in the summer and to warm it up in the winter. Has anyone had any experience with this?
David S. :Welcome to Permies.com, and to our sister site Richsoil.com, Air Tubes have a mixed track record especially in more humid climates- I am providing
the link be low to help you navigate through the mass of materials but here at Permies and the rest of the Web !
Thanks for the introduction to the forum. I am thinking about digging a trench 6 feet deep to lay pipe. I will also put 55 gallon drums filled with water down there and wrap the pipe around them (the pipe being 4 inch drain pipe). I am hoping that because water is a great way to transfer heat that it will really help cool/heat the air in the pipe. I am also thinking about putting close to a foot mulch at ground level to further help with cooling the ground. What are your thoughts about this?
I was wondering about this my self, searched for answers, found your post.
Condensation in the earth tube could be an issue. Some greenhouse designs avoid this by using perforated tubing.
This prevents the pooling of water.
I'm working on a similar design for my greenhouse, but I'm in a heating climate so we're using the tubes to dump heat into the earth below and around the greenhouse to help hear it in the winter. Always use perforated drain pipe. I wouldn't bother fooling around with barrels of water underground (that's what I understood your post to suggest), not much Mass difference than the surrounding soil. One thing you have to keep in mind is the velocity and dwell time of the air in the tubes, and whether you're looking to cool passively or with electric fans. For a climate battery, this means burying 4" perf ads tubing every couple feet on center and every 1' vertically, and connecting to much larger plenums at each end. For us, a major part of the design is the condensation of water vapor in the running, and the subsequent release of stored energy from the water vapor and into the soil. I imagine that would be less of a factor in Arizona.
My place is in NE Arizona.
The pit greenhouse is five feet deep with a clear plastic roof.
When i was there a month ago i had thermometers everywhere: outside, at the ceiling,at the floor,in the hydroponic trays and in this drum.
I would get up before sunrise to check every temperature and when it was 35° outside the drum was 60°.
This was enough for me to think about pumping the water from the drum through a car radiator with a fan attached to warm in winter and cool in summer.
Right now the drum water is pumped through black irrigation hose that's just under the plastic roofing and feeds into the hydroponic trays to overflow back into the drum.
I would be VERY interested in the condensation that collects in an earth air tunnel.
Thanks for sharing this info and photos. I might suggest that when trenching that deep and working down in them to use shoring. These kinds of trenches collapse very easily and often without warning. I've laid plenty of clay sewer pipe and seen the ditches collapse when no shoring is used. Shoring is really not a luxury, but a necessity. I'm not trying to be a debbie downer here, but these trenches are extremely dangerous.