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Chapter 9. Cutting Carbon Emissions in Half: Energy from the Earth
When we think of renewable energy, we typically think of sources derived from the sun, either directly or indirectly, such as solar heating, solar electricity, wind power, and hydropower, or sources of biological origin, such as wood and crop residues. But the earth itself is a source of heat energy (mostly from radioactivity within the earth), which gradually escapes either through conduction or through hot springs and geysers that bring internal heat to the earth's surface. The use of geothermal energy is sustainable as long as its use does not exceed the rate of generation. It is also inexhaustible and will last as long as the earth itself.
Geothermal energy is used both to generate electricity and as a source of heat for direct use, such as with space heating for greenhouses, aquaculture, and industrial processes, and with heat pumps. After Italy pioneered the use of geothermal energy to generate electricity in 1904, the practice spread to some 22 countries. The global capacity of 8,000 megawatts in 2000 represents a 37-percent growth over the 5,800 megawatts available in 1990.34
Two countries—the United States with 2,200 megawatts and the Philippines with 1,900 megawatts—account for half of world generating capacity. (In the Philippines, geothermal provides 27 percent of the country's electricity supply.) Most of the remainder is concentrated in five countries: Italy, Mexico, Indonesia, Japan, and New Zealand.35
The direct use of geothermal heat for various purposes is even larger, equivalent to 12,000 megawatts of electricity generation. Some 30 countries account for most of the world's direct use of geothermal energy. Its use in heat pumps, which extract and concentrate heat from warm water for various uses, is the largest single use.36
Iceland and France dominate the use of geothermal energy for space heating. In Iceland, 85 percent of the country's 290,000 people use geothermal energy to heat their homes, saving $100 million per year from avoiding oil imports. Geothermal energy accounts for more than one third of Iceland's energy use. During the decade following the two oil price hikes in the 1970s, some 70 geothermal heating facilities were constructed in France, providing both heat and hot water for some 200,000 housing units. In the United States, individual homes are supplied directly with geothermal heat in Reno, Nevada, and in Klamath Falls, Oregon. Other countries that have extensive geothermally based district-heating systems include China, Japan, and Turkey.37
Geothermal energy is an ideal source of heat for greenhouses, particularly in northern climes. Russia, Hungary, Iceland, and the United States all use geothermally heated greenhouses to produce fresh vegetables in winter.38
Some 16 countries use geothermal energy for aquaculture. Among these are China, Israel, and the United States. In California, for example, 15 fish farms produce tilapia, striped bass, and catfish with warm water from underground. This enables farmers to produce larger fish in a shorter period of time and to produce without interruption during the winter. Collectively these California farms produce 4.5 million kilograms of fish per year.39
The number of countries turning to geothermal energy both for electricity and for direct use is increasing rapidly. So, too, is the range of uses. Once the value of geothermal energy is discovered, its use is often quickly diversified. Romania, for example, uses its geothermal energy for district heating, for greenhouses, to produce hot water for dwellings, and to supply industrial hot water for factories. With heat pumps, it is now possible to treat the earth as both a heat source and a sink to provide heating in winter and cooling in summer.40
Geothermal energy is widely used for bathing and swimming. Japan, for example, has 2,800 spas, 5,500 public bathhouses, and 15,600 hotels and inns that use hot geothermal water. Iceland has some 100 public swimming pools heated with geothermal energy. Most are open-air pools used the year-round. Hungary heats 1,200 swimming pools with geothermal energy.41
The potential of geothermal energy is extraordinary. Japan alone has an estimated geothermal electric-generating capacity of 69,000 megawatts, enough to satisfy one third of its electricity needs. Other countries bordering the Pacific with a vast potential—in the so-called Ring of Fire—include Chile, Peru, Ecuador, Colombia, all of Central America, Mexico, the United States, and Canada in the East Pacific and Russia, China, South Korea, the Philippines, Indonesia, Australia, and New Zealand in the West Pacific. Other geothermally rich countries include those along the Great Rift of Africa and the Eastern Mediterranean. Fortunately, many countries now have enough experience and engineering capacity to tap this vast resource.42
34. International Geothermal Association, "Electricity Generation," at iga.igg.cnr.it/electricitygeneration.php, updated 27 April 2002.
35. Ibid.; Philippines share from World Bank, "Geothermal Energy," prepared under the PB Power and World Bank partnership program, at www.worldbank.org/html/fpd/energy/geothermal, viewed 23 January 2003.
36. World Bank, op. cit. note 35.
37. John W. Lund and Derek H. Freeston, "World-wide Direct Uses of Geothermal Energy 2000," Geothermics, vol. 30 (2001), pp. 34, 51, 53; population from United Nations, op cit. note 13.
38. Lund and Freeston, op. cit. note 37.
39. Ibid.; California in World Bank, op. cit. note 35.
40. World Bank, op. cit. note 35.
41. Lund and Freeston, op. cit. note 37, pp. 46, 53.
42. Japan from Hal Kane, "Geothermal Power Gains, " in Lester R. Brown et al., Vital Signs 1993 (New York: W.W. Norton & Company, 1993), p. 54; DOE, EIA, "Japan," EIA Country Analysis Briefs, at www.eia.doe.gov/emeu/cabs, updated April 2002; other potential in World Bank, op. cit. note 35.
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