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Natural heat within the earth is geothermal energy. Reliable power is generated from underground water which seeps below earth’s surface near an existing volcano. Reservoirs of molten rock deep under 3,000 meters heat the water. Similarly wells drilled for crude oil and natural gas are used to recover the water. After recovering the water, steam and hot water is separated. Cleaned steam is dispatched to the power plant. Separated water is sent back to the reservoir to generate steam again. At some locations of the globe, deep fractures in the earth’s crust allow molten rock close enough to heat the water going underground. Geothermal energy provides renewable power with no chemical pollutants or waste, and the water can be injected again and again underground. Geothermal energy in this sense is practically unlimited.
Chevron is currently the largest geothermal energy producer in the world. They began geothermal operations in 1960 in the western US. Further discoveries and commercial production were introduced in the Philippines and Indonesia by 1990. They have a production capacity of 1,273 megawatts of geothermal renewable energy - enough to meet the requirements of millions of people - and this is just the beginning of untapped geothermal renewable energy. Gradually many other companies are chipping in because Geothermal Energy can contribute substantially to meet the ever increasing demand of energy across the globe.
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Working with the Geothermal Energy Sources
Geothermal steam power plants consist of three types: dry steam, flash steam, and binary cycle.
A dry steam power plant system directly uses steam from underground wells. The steam is cleaned before feeding it to turbine engine. These plants are found in northern California and in Wyoming in a place nicknamed "Geysers."
Most common flash steam power plants use geothermal reservoirs of water of temperatures greater than 180 degrees C. Pumps are not required to tap this hot water as it flows up under its own pressure. Steam is formed automatically during the upward flow. The steam is cleaned and water is injected back into the wells. Hot water can also be used for many applications. This is a self-sustainable vital power source.
Binary systems adopt a lower temperature of water in a range of 107 to 180 degrees C. A certain organic working fluid uses heat from boiling water. The fluid gets vaporized in the heat exchanger and is then used to activate the turbine. The used water is reheated and working fluid is kept separately.
We get geothermal energy, which is clean sustainable heat, from the earth. This resource of energy ranges from shallow ground hot water to hot rock found miles below earth’s surface. As we go deeper, we find molten rock of extremely high temperatures called magma. About ten feet of earth’s shallow ground maintains a constant temperature of about 16 degrees C (60.8° F). Geothermal heat pumps are used to warm buildings from a network of heat exchanger pipes buried adjacent to buildings. This process is reversed in the summer to cool the buildings. This system provides a free source of hot air in winter and cool water during summer.
Natural geothermal hot springs caused by steam escaping at the site are found in Nevada. Most geothermal reservoirs are found in Alaska and Hawaii. Electricity is generated by drilling into the underground reservoirs. Useful applications are harnessed for plantations in greenhouses, farms houses, and several industrial processes. At most locations everywhere below earth’s surface, hot rock resources are found at depths up to five miles. Cold, fresh water from the local area can be diverted into fractured rocks to generate steam power for turbine engines that produce useful electricity for the locality. Magma rocks located even deeper in the earth are a less-often tapped direct source of geothermal superheated steam.
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Pros and Cons of Geothermal Energy
Every source of energy has certain good and bad aspects associated with it. In this section we will have a look at the pros and cons of Geothermal Energy.
Limitless free steam is a versatile geothermal source of power for generating electricity. This technology is far simpler than electricity produced from solar energy. The electrical power supply is several megawatts produced by steam turbines. Excess heat energy can also be used for cooling and heating houses. Geothermal energy is mostly available from volcano activity. Hence there are many geothermal plants around the world's "Fire Ring" zone.
The greatest disadvantage is that extensive deep drilling of the earth is impossible and access to deep earth for extracting steam requires detonators to explode it, which means one needs expertise and skilled workforce to make the best use of energy trapped in the earth's surface. The Lusi mud volcano in Indonesia is one such example when hot mud started flowing out of one of the wells during excavation. Efforts to plug the well only aggravated the whole situation.
- Geothermal Energy Association, A Guide to Geothermal Energy and Environment (PDF)
- Idaho National Laboratory, The Future of Geothermal Energy (PDF)
- Lusi - Greatest Disaster of the Oil and Gas Industry- Lumpur Sidoarjo is a mud volcano in Indonesia that erupted during drilling for a natural gas well. It has been spewing hot mud, inundating villages, and displacing thousands of people for the last four years.