Alternative Energy Sources

Geothermal energy is heat generated naturally in the interior of the earth, and can be used either directly, as heat, or indirectly, to generate electricity. Geothermal energy can be used to generate electricity by the flashed-steam method, in which high-temperature geothermal brine is used as a heat source to convert water injected from the surface into steam. The steam is used to turn a turbine and generator, which produces electricity. When geothermal wells are not hot enough to create steam, a fluid that evaporates at a lower temperature than water, such as isobutane or ammonia, can be used in a closed loop in which the geothermal heat evaporates the fluid to run a turbine and the cooled vapor is recondensed and reused. More than 20 countries utilize geothermal energy, including Iceland, Italy, Japan, Mexico, Russia, and the United States. Unlike solar energy and wind power, geothermal energy may contribute to air pollution and may raise dissolved salts and toxic elements such as mercury and arsenic to the surface.