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?
If the heap was under the bed, convection would keep the warm water circulating without a pump. Sort of like a solar batch heater, but with the collector embedded in the heap. Is this feasible or will the growing area be on the ground?
Seed the Mind, Harvest Ideas.
I figured the growing bed would be raised up onto a table. The compost heap would be under the table.
If the growing bed was on the ground, You would have to dig a pit to fill with compost.
If you included plumbing to circulate warmth, a piece of it being exposed would help. The exposed section would serve as a cooler/condenser. Cool water is more dense, will fall, Warm water is less dense, will rise. If the plumbing was set up similar to a rectangle, with the right side exposed, circulation would be enhanced. I think there would not be a great deal of flow, but you don't need much.
The compost heap would settle as it decomposes. If the growing bed was raised on a table, the sides around the legs could be enclosed to contain the warmth, as well as the heap. If the growing bed was on the ground, I would expect it to sag along with the heap. A four foot wide bed is the perfect size for a compost heap/growing bed combination.
My Future Evil Plan has a catfish tank in the greenhouse. The water going into the tank as it is changed daily would be heated with the sun (wood fired backup). The well pump would be the power source for moving the water. The warm tank keeps the greenhouse cozy. Water from the tank as it is changed goes to the plants to provide nutrients from the fish manure. One small pump is needed to move the water from the tank to the plants.