About
Geothermal Energy
Geothermal
energy is the heat from the Earth. It's clean and sustainable. 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.
Almost
everywhere, the shallow ground or upper 10 feet of the Earth's surface maintains a nearly constant temperature between 50°
and 60°F (10° and 16°C). Geothermal heat pumps can tap into this resource to heat and cool buildings. A geothermal heat pump
system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow
ground near the building. In the winter, the heat pump removes heat from the heat exchanger and pumps it into the indoor air
delivery system. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger.
The heat removed from the indoor air during the summer can also be used to provide a free source of hot water.
The
Earth's heat-called geothermal energy-escapes as steam at a hot springs in Nevada.
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.
Hot
dry rock resources occur at depths of 3 to 5 miles everywhere beneath the Earth's surface and at lesser depths in certain
areas. Access to these resources involves injecting cold water down one well, circulating it through hot fractured rock, and
drawing off the heated water from another well. Currently, there are no commercial applications of this technology. Existing
technology also does not yet allow recovery of heat directly from magma, the very deep and most powerful resource of geothermal
energy.
Many
technologies have been developed to take advantage of geothermal energy - the heat from the earth. NREL performs research
to develop and advance technologies for the following geothermal applications:
Geothermal
electricity production
Generating
electricity from the earth's heat.
Geothermal
direct use
Producing
heat directly from hot water within the earth.
Geothermal
heat pumps
Using the shallow
ground to heat and cool buildings.
Links
http://www.est.org.uk/myhome/
The Energy Saving
Trust
