Geothermal systems

Geothermal systems use the heat in the earth’s crust, which can result in temperatures of up to about 90OC at the bottom of a 3km well – about the current maximum depth for such installations, to drive more or less conventional steam turbines and thus generate electricity. Suitable areas for installations are however, very sparsely distributed and are basically around the Pacific “ring of fire” and other areas where tectonic plate boundaries are relatively near the surface, resulting in a somewhat limited potential for future growth. The largest producers of geothermal electricity are North America, particularly California and Mexico, and the Philippines and Indonesia, whilst in the future other Central American states such as El Salvador, Costa Rica and Nicaragua could expand their production significantly. Total capacity was only about 8GW in 2004.