Schematic illustration of Hot Dry Rock principle geothermal power plant.

A facility that uses geothermal energy to generate electricity. Geothermal power plants are built in places where there is a suitable geothermal reservoir near the surface, heated by heat from the earth’s interior. This may be a hot rock into which the geothermal power plant pumps water and then uses it (hot dry rock method), or it may be a reservoir of hot groundwater which the power plant uses directly to drive a turbine (dry steam or flash steam method) or to heat another heat-transfer medium (binary cycle power plant).