7. Geothermal electricity

In certain favorable zones, water at high temperatures can be found by drilling deeper or shallower boreholes. In the 150 to 350°C range, this is known as high-energy geothermal energy. The water is pumped to the surface and passed through heat exchangers; the steam produced is then turbined in the same way as in conventional thermal power plants.

Cumulative installed capacity reaches around 8 GW electric for a total annual production of around 50 · 10 ⁹ kWh. The forecast is for 18.7 GW in 2010 (Système Solaire magazine, June 2002). In the Philippines alone, 1.9 GW contribute 25% of electricity production. Italy has a generating capacity of 790 MW for...