I have this idea to have a jean pain compost pile heating a raised bed in a greenhouse. I would build the pile in the greenhouse, and the piping full of water that runs through the pile to be heated up would be a closed loop, pushed by an electric pump, running from the compost pile through the bottom of the raised bed, very much like radiant floor heating, and back into the compost pile. It could have a thermostat to turn the pump on and off, monitoring the soil temp, set to keep it at 70 degrees. It's not super permaculture, since it's using an electric pump (and a greenhouse, some would say), but it seems like it wouldn't take a whole lot of energy to have a pump push water mostly horizontally. I don't know if there is a pump out there that is designed to handle pushing water in a closed loop. Does anyone know if a pump like this
might do the job? What does anyone think about this idea in general. If I try it out, I'll definitely report back. It'd be pretty nice to be able to eat greens from the backyard through the winter, eh?