Geothermal power, “geo” meaning “from the earth” and “thermal” meaning “heat”, is energy that is derived from the heat of the earth's core. This form of energy is not only environmentally friendly and predictable; it offers a constant, dependable and renewable source of energy.
Geothermal energy is a simple notion: extract heat that occurs naturally in the earth’s core and use it to moderate ambient surface temperatures or, in cases where the heat source is sufficient, use the steam to power turbines and create electricity.
Fifty years of geothermal energy
The Geysers geothermal area is the largest dry-steam geothermal steam field in the world. The Geysers, the first geothermal power plant in the United States, is located in the Mayacamas Mountains just north of San Francisco, California; this geothermal plant celebrated its 50th year in 2010.
A particularity of The Geysers
Deep in the earth’s surface there is magma and the temperature is very high. In volcanically active areas, the magma is very close to the earth’s surface. In the Mayacamas Mountains, the magma is believed to be roughly 4 miles below the surface. The existing heat radiates through the surfaces of the earth, warming layers of rocks and any water that is located within these rocks. At the surface, some of this heated water rises in the form of geysers, hot springs and fumaroles.
A distinctive feature at The Geysers is the presence of a cap rock; this layer of tight, unfractured rock captures water in a pool. The water is heated to a boil and then steams.
To extract this naturally occurring steam, two mile wells have been drilled through this cap rock, to then transfer this steam to one of fifteen power plants at The Geyser complex. Once the steam is purified of any particles that could break turbine blades, the steam is put to work rotating turbine generators at the power plants to create electricity.
This Geothermal power complex requires approximately two million pounds of steam/hour to run a 110 megawatt generating unit. Once the steam has gone through a turbine, it is cooled and converts back to water; roughly 75% of the water is lost in condensation, the remaining 25% is returned to the pool.
Geothermal energy for the future
Geothermal and the benefits of hot springs and fumaroles have been used in North America for healing, cooking and heating for some 10 000 years. As the world continues to turn to cleaner and more economical alternative energies sources, geothermal advocates are looking into the possibility of generating artificial steam by pumping water deep into the hot, dry rocks. This method, known as “enhanced, or engineered geothermal systems”, may likely be the only way that geothermal could succeed in becoming a more important contributor to the world’s existing power needs. Improving the contribution of geothermal energy requires that technologies from the oil and gas drilling industries be employed and that rocks be fractured using high-powered water streams to generate steam to run the power turbines.
Well drilling for geothermal energy
Certain countries have already actively started benefiting from geothermal resources resulting from the presence of volcanic activity on their soil; thanks to drilling and power stations, roughly 18% of the electricity in the Philippines is generated from geothermal energy, about 25% in Iceland and some 26% in El Salvador.
Geothermal energy, although nearly free of carbon emissions, more dependable than wind and solar energy and possessing a bigger energy potential than fossil fuels, is still only able to sustain a small portion of the world’s energy needs. It is believed that the drilling of engineered geothermal systems will be the driving force to making geothermal energy more prominent.
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http://news.nationalgeographic.com/news/news/energy/2010/12/101228-geothermal-energy-pick-up-real-steam-/
http://www1.eere.energy.gov/geothermal/geysers.html