Geothermal energy is renewable heat energy from deep in the earth.
Use of hydrothermal energy is economic today at a number of high-grade sites. Earth energy is used by geothermal heat pumps. F to more than 700deg. F, is brought from the underground reservoir to the surface through production wells, and is flashed to steam in special vessels by release of pressure. The steam is separated from the liquid and fed to a turbine engine, which turns a generator.