How is geothermal energy obtained?

Geothermal energy is contained in the intense heat that continually flows outward from deep within the earth. From the earth’s surface down through the crust, the normal temperature gradient (the increase of temperature with increase of depth) is 100 to 300 Celsius per kilometre. In certain areas, water seeping down through cracks and fissures in the crust comes in contact with this hot rock and is heated to high temperatures. Some of this heated water circulates back to the surface and appears as hot springs and geysers. However, the rising hot water may remain underground in areas of permeable hot rock, forming geothermal reservoirs. These, which may reach temperatures of more than 3,500 Celsius,can provide a powerful source of energy. Geothermal reservoirs within about 5 kms of the Earth’s surface can be reached by drilling a well. The hot water or steam from wells can be used to turn turbine generators to produce electricity. A power plant that uses this natural source of hot water or steam is called a geothermal power plant. Thus, in some cases, it is viable to capture geothermal energy and this renewable source of energy becomes obtainable.