Geothermal power (from the Greek words geo, meaning earth, and therme, meaning heat) is energy generated by heat stored beneath the Earth's surface or the collection of absorbed heat in the atmosphere and oceans.


Prince Piero Ginori Conti tested the first geothermal generator on 4 July 1904, at the Larderello dry steam field in Italy.[1] The largest group of geothermal power plants in the world is located in The Geysers, a geothermal field in California.[2] As of 2007, geothermal power supplies less than 1% of the world's energy.



Three different types of power plants - dry steam, flash, and binary - are used to generate electricity from geothermal energy, depending on temperature, depth, and quality of the water and steam in the area. In all cases the condensed steam and remaining geothermal fluid is injected back into the ground to pick up more heat. In some locations, the natural supply of water producing steam from the hot underground magma deposits has been exhausted and processed waste water is injected to replenish the supply. Most geothermal fields have more fluid recharge than heat, so re-injection can cool the resource, unless it is carefully managed.