Geothermal energy is just one of many renewable or sustainable sources of energy that is getting a lot of focus today. Geothermal energy is heat harnessed from the Earth. Deep inside the Earth lies hot water and steam that can be used to heat our homes and businesses and generate electricity cleanly and efficiently. It's called geothermal energy -- from the Greek words geo, or "earth," and therme, meaning "heat". Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.
In the United States, most geothermal reservoirs of hot water are located in the western states, Alaska, and Hawaii. Wells can be drilled into underground reservoirs for the generation of electricity. Some geothermal power plants use the steam from a reservoir to power a turbine/generator, while others use the hot water to boil a working fluid that vaporizes and then turns a turbine. Hot water near the surface of Earth can be used directly for heat. Direct use applications include heating buildings, growing plants in greenhouses, drying crops, heating water at fish farms, and several industrial processes such as pasteurizing milk.
While geothermal energy is not always ideal to implement as a means of power generation due its functionality and practicality being determined entirely by whether or not geothermal heat can be accessed, it can be highly effective in areas where fuel can be accessed. These areas are located in places with high tectonic activity where hot water and/or steam is carried to the Earth's surface or can be reached at shallow depths. However despite geothermal energy being limited in nature it is one of the most powerful methods for power generation due to it's consistent fuel availability and it's high efficiency rate. In countries where geothermal heat is plentiful such as Iceland, El Salvador, New Zealand, Kenya and the Philippines, geothermal energy covers for a significant share of all electricity generation. Geothermal heat can also be used to heat buildings for free and with zero carbon emissions such as in Iceland where 90% of all heating demands are met by geothermal energy.
For: electrical power derived from geothermal energy, see Geothermal power.