Geothermal: Getting Energy from the Earth

The heat in the upper six miles of the earth’s crust contains 50,000 times as much energy as found in all the world’s oil and gas reserves combined. Despite this abundance, only 10,700 megawatts of geothermal electricity generating capacity have been harnessed worldwide.

Partly because of the dominance of the oil, gas, and coal industries, which have been providing cheap fuel by omitting the costs of climate change and air pollution from fuel prices, relatively little has been invested in developing the earth’s geothermal heat resources. Over the last decade, geothermal energy has been growing at scarcely 3 percent a year.

Roughly half the world’s existing generating capacity is in the United States and the Philippines. Indonesia, Mexico, Italy, and Japan account for most of the remainder. Altogether some 24 countries now convert geothermal energy into electricity. El Salvador, Iceland, and the Philippines respectively get 26, 25, and 18 percent of their electricity from geothermal power plants.

The potential of geothermal energy to provide electricity, to heat homes, and to supply process heat for industry is vast. Among the countries rich in geothermal energy are those bordering the Pacific in the so-called Ring of Fire, including Chile, Peru, Colombia, Mexico, the United States, Canada, Russia, China, Japan, the Philippines, Indonesia, and Australia. Other geothermally rich countries include those along the Great Rift Valley of Africa, such as Kenya and Ethiopia, and those around the Eastern Mediterranean.

Beyond geothermal electrical generation, an estimated 100,000 thermal megawatts of geothermal energy are used directly—without conversion into electricity—to heat homes and greenhouses and as process heat in industry. This includes, for example, the energy used in hot baths in Japan and to heat homes in Iceland and greenhouses in Russia.

An interdisciplinary team of 13 scientists and engineers assembled by the Massachusetts Institute of Technology (MIT) in 2006 assessed U.S. geothermal electrical generating potential. Drawing on the latest technologies, including those used by oil and gas companies in drilling and in enhanced oil recovery, the team estimated that enhanced geothermal systems could be used to massively develop geothermal energy. This technology involves drilling down to the hot rock layer, fracturing the rock and pumping water into the cracked rock, then extracting the superheated water to drive a steam turbine. The MIT team notes that with this technology the United States has enough geothermal energy to meet its energy needs 2,000 times over.

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