Geothermal heat is collected using the 'flywheel' effect, meaning two adjacent areas at different temperatures will attempt to reach parity by exchanging higher energy to lower energy. In this case, heat energy from underground soil naturally exchanges with cooler air being piped through the area, until the air temperature in the pipes is equalized by absorbing heat. This heat exchange is completely passive, thanks to the laws of thermodynamics.
Homeowners typically prefer to maintain a temperature higher than 60 degrees F, so in a passive geothermal setup, the addition of an auxiliary residential heat pump is common. However, the warmer air from the passive geothermal heat allows a heat pump to work much more effectively, meaning a house can be maintained at a comfortable temperature at a very low cost.
