All of the energy we could ever use sits deep below our feet. Geothermal energy is the only renewable resource that is not derived by the sun. Radioactive decay of unstable elements such as thorium and uranium in the earth’s core releases heat, which remain trapped deep below the earths surface. In areas of deep faults and fissures groundwater is able to seep down to heated rocks. The contact causes the water to heat up and rise back to the surface where it can be captured for use.
Greeks and Romans built public baths over hot springs. Native Americans use hot springs for cooking. Early settlers in Oregon and Idaho captured the hot ground water and heated their homes with it. Since 1960 large reservoirs of Geothermal steam and other hot water reservoirs in the U.S. west have been tapped to generate 3,000 megawatts of electricity.9
There are four types of geothermal resources. Hot dry rocks, magma and geopressured brines are still untapped and un-researched areas which could prove quite beneficial in the future, while hydrothermal reservoirs are more commonly utilized. Hydrothermal reservoirs have two basic ingredients water and steam. Pressurized steam that is emitted from drilled wells has the ability to turn a turbine to generate electricity. Hot water from geothermal reservoirs can be used for heating homes, drying food and paper, pasteurizing milk and generating electricity. In Elko, Nevada geothermal hot water is pumped into homes and is used to provide clean and reliable heat.9
Geothermal energy provides an unlimited supply of clean energy. It provides no air or water pollution and any salts or minerals which are waste products can be pumped deep into the ground where they will cause no harm.
Geothermal resources have the potential to be overexploited when heat is removed faster than natural reactions replace it. If this is the case output of energy may fall if the number of wells increases for a given area. Start up and development costs can be expensive as well as maintenance costs due to corrosion. In some rare cases ground settlement has taken place over some reserves.9