(This is the second of a 10-part series. Previous post here.)
At the University of New Hampshire, my Soils Science teacher, Art LeClair, turned me on to solar energy. He was my favorite teacher – enthusiastic, intelligent, knowledgeable, experimental, fun and funny. I naturally absorbed what he conveyed.
On a winter field trip, our Soils class visited Solar Survival in Harrisville, NH. This was the home and lab of Leandre and Gretchen Poisson, authors of ‘Solar Gardening: Growing Vegetables Year-Round the American Intensive Way.’ They grew food all winter in frigid, frozen, snowed-in northern New England using solar pods, which they developed.
A solar pod is a 4′x8′ cold frame surrounded on the outside with rigid foam insulation and buried partially in the ground. The lid is not a piece of glass or an old window, like a typical cold frame. It is an arch of two layers of Kalwall® greenhouse glazing with Angel Hair, a fine and translucent, yet heavy duty, insulation, sandwiched in between.
The thermal mass inside the pod is a black 55-gallon drum filled with water and laid on its side at the north end. During the day, the water absorbs the sun’s heat and slowly radiates it back out over night.
This photo from the book is a series of pods lined up end to end. You can clearly see the drum laying on its side at the far end of the front center pod.
The translucence of the insulation is key. It must transmit enough solar energy in low-light winter for healthy plant growth and to warm the water in the drum to a high enough temperature that it can radiate heat on a cold New Hampshire night.
My friend, Hugh, and I partnered up in lab to build a solar pod. We didn’t get to grow anything in it, but witnessing that process at Solar Survival was proof enough that it worked. After that field trip and construction project, I was completely sold on solar energy!
Art shared another source of information with us, a book by Rick Fisher and Bill Yanda of Zomeworks in Santa Fe, New Mexico, called ‘The Food and Heat Producing Solar Greenhouse.’ It was published in 1980 and already out of print the following year. Solar hadn’t caught on yet, so I guess it was not deemed an important book. I tracked down a copy, though (remember, this was way before Amazon and used books!), and studied it as though I was having an exam on it. I now have a dog-eared copy (photo), which I repeatedly refer to, because, like I said last week, solar principles never change.
After my first semester at UNH, my love for solar construction and New Mexico was burgeoning.
(Glazing and insulation materials to build Poisson’s solar pod and solar cones are available from Solar Components.
(Originally published at www.greenbuyguide.com.)
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