Geothermal Heat Pumps - Heating Mode

In winter, fluid passing through this vertical, closed loop system is warmed by the heat of the earth; this heat is then transferred to the building.

Geothermal heat pumps use the stable temperatures of the ground (often vertical boreholes typically are 100 to 400 feet deep) as a heat source to warm buildings in winter and as a heat sink to cool them in summer.  Also called ground-source heat pumps or Geoexchange units.