A while back, [Erich]’s oil heating system was due for a few repairs. Given the increasing price of fuel oil, and a few incentives from his Swiss government, he decided to go with a more green heating solution – geothermal heating. The system works well in the winter, but it’s basically useless in the summer. [Erich] decided to put his 180 meter investment to work for the summer heat, and made his geothermal heating system into a cooling system with a fairly low investment and minimal cost.
The stock system works by pumping cold liquid from [Erich]’s under floor heating into the Earth. In winter, the surface is always colder than the ground, thus heating [Erich]’s home. In the summer, the situation is reversed, with the cool earth insulated by the baked surface. All that was required to reverse the heating system was a few slight modifications to the heating controller.
Stock, [Erich]’s heat pump controller doesn’t have the capability to run the system in reverse, so he turned to a Freescale board to turn the compressor off and the pump on. With the additions, [Erich] is using 50 Watts to pump 1.5 kW of heat directly into the Earth below, a fairly efficient cooling system that’s basically free if you already have a geothermal setup.