Viewing post #741814 by cycadjungle

LariAnn said:Burying the barrel is clearly the trick here, as it helps conserve heat and also draws on the much higher temperature of the soil to keep the water from cooling too fast. I'm not clear, though, on why the need for the half barrel cover unless it is just to add a little extra insulation to the setup.

I wonder how much better this would work if you had an aquarium water heater in the barrel all night long - I'd think it wouldn't cost much and would yield more heat.

I used the half barrel to increase the amount of air within the barrel system. With this, there is the equivalent of 45 gallons of heated air plus the 40 gallons of "warm" water. The heater would add to the higher temperature of the water, but I wanted to make something that works totally without any power or machines of any kind. For that matter, I could use a solar panel to remotely produce electricity that could be used to heat the greenhouse.