I'm toying with some ideas for keeping water de-iced on all but the coldest days, and found myself looking at old solar hot water designs. Then I remembered thermal mass ideas for greenhouses. Anyone either play with/have any input. I can think of a legion of reasons why it probably won't work, or is impractical with the number of coops I have active. But the kernel of a single mad idea sometimes yields results that aren't completely stupid.