World geothermal power generation nearing eruption

With fossil fuel prices escalating and countries searching for ways to reduce oil dependence and greenhouse gas emissions, capturing the earth’s heat for power generation is garnering new attention. First begun in Larderello, Italy, in 1904, electricity generation using geothermal energy is now taking place in 24 countries, 5 of which use it to produce 15 percent or more of their total electricity. In the first half of 2008, total world installed geothermal power capacity passed 10,000 megawatts and now produces enough electricity to meet the needs of 60 million people, roughly the population of the United Kingdom. In 2010, capacity could increase to 13,500 megawatts across 46 countries—equivalent to 27 coal-fired power plants.

Originating from the earth’s core and from the decay of naturally occurring isotopes such as those of uranium, thorium, and potassium, the heat energy in the uppermost six miles of the planet’s crust is vast—50,000 times greater than the energy content of all oil and natural gas resources. Chile, Peru, Mexico, the United States, Canada, Russia, China, Japan, the Philippines, Indonesia, and other countries along the Ring of Fire (an area of high volcanic activity encircling the basin of the Pacific Ocean) are rich in geothermal energy. Another geothermal hot spot is the Great Rift Valley of Africa, which includes such countries as Kenya and Ethiopia. Worldwide, 39 countries with a cumulative population of over 750 million people have geothermal resources sufficient to meet all their electricity needs. (See data.)

Typically, power generation using the earth’s heat required underground pockets of high-temperature water or steam to drive a steam turbine. Now, new technologies that use liquids with low boiling points in closed-loop heat exchange systems allow electricity to be generated at much lower temperatures. This breakthrough is making geothermal power generation viable in countries such as Germany that are not known for their geothermal resources and is one reason why the number of countries using the earth’s heat to generate electricity could almost double by 2010.

One advantage of geothermal power plants, beyond the benefit of producing electricity from a low-carbon, indigenous energy source with no fuel costs, is that they provide baseload power 24 hours a day. Storage or backup-power is not required.

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