Piggybacking off of tantalizing and suggestive data from our experiments at Tamera Solar Test Field with a black IBC insulated on three sides and covered with two layers of clear stretch wrap plastic on the south and west sides, we decided to take one of our soy-based polyurethane foam insulated biodigesters up to Kathy Puffer's Homestead Ecosystem location in Tillson NY, cut out the foam on the south facing side, paint the IBCs exposed wall black and foam in a double pane glass window.
Preliminary results show favorable solar gain on sunny days, keeping the digester at or near 25 C even when ambient drops to 3 Celsius at night.
There are still thermal losses at night through the window (which we are covering with a blanket) and through the top of the digester where it is uncovered (the lid and the feeding pipes, and it may ot stay active all winter, particularly during cloudy times, but it certainly helps in sunny times and will definitely boost production in fall and spring even if it slows dramatically during the winter. We suggest this now as a standard feature in IBC builds; the marginal cost of an old double pane window (which we got used) is negligible compared to the gains.
