Geothermal energy is energy from the hot interior of the earth. Fissures in the earth’s crust allow water heated by geothermal energy to rise naturally to the surface at hot springs and geysers. Wells drilled into the earth allow heated steam or water to escape to the surface in a controlled manner to operate steam turbines and electricity generators. In a different type of application, the temperature of the earth or ground water relatively near the earth’s surface is used as a heat source and sink for “geothermal” heat pumps that heat and cool buildings.
Geothermal energy accounted for about 5% of total renewable energy consumption in 2007. Geothermal power plants in California, Hawaii, Nevada, and Utah generated approximately 14.4 billion kWh of electricity in 2004. Hot springs have long been used at resorts and spas, and for heat in buildings, greenhouses and aquaculture facilities, and in industrial processes. There are about 500,000 geothermal heat pumps in the United States, and the number is increasing by around 37,000 per year.
Source: Energy Information Administration