Original:  More recent technological advances have dramatically reduced costs and thereby expanded the range and size of viable resource and in 2021 the U.S. Department of Energy estimates that geothermal energy from a power plant "built today" costs about $0.05/kWh. Worldwide, 13,900 megawatts (MW) of geothermal power was available in 2019. An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating, space heating, spas, industrial processes, desalination and agricultural applications as of 2010. Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, plate boundary movement and interest rates. Pilot programs like EWEB's customer opt in Green Power ProgramGreen Power . eweb.org show that customers would be willing to pay a little more for a renewable energy source like geothermal. About 100 thousand people are employed in the industry. The adjective geothermal originates from the Greek roots (), meaning Earth, and (), meaning hot. History The oldest known pool fed by a hot spring, built in the Qin dynasty in the 3rd century BCE Hot springs have been used for bathing at least since Paleolithic times. The oldest known spa is a stone pool on China's Lisan mountain built in the Qin Dynasty in the 3rd century BCE, at the same site where the Huaqing Chi palace was later built. In the first century CE, Romans conquered Aquae Sulis, now Bath, Somerset, England, and used the hot springs there to feed public baths and underfloor heating. The admission fees for these baths probably represent the first commercial use of geothermal power. The world's oldest geothermal district heating system in Chaudes-Aigues, France, has been operating since the 15th century. The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy. In 1892, America's first district heating system in Boise, Idaho was powered directly by geothermal energy, and was copied in Klamath Falls, Oregon in 1900. The first known building in the world to utilize geothermal energy as its primary heat source was the Hot Lake Hotel in Union County, Oregon, whose construction was completed in 1907. A deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the same time. Charlie Lieb developed the first downhole heat exchanger in 1930 to heat his house. Steam and hot water from geysers began heating homes in Iceland starting in 1943. Global geothermal electric capacity. Upper red line is installed capacity; lower green line is realized production. In the 20th century, demand for electricity led to the consideration of geothermal power as a generating source. Prince Piero Ginori Conti tested the first geothermal power generator on 4 July 1904, at the same Larderello dry steam field where geothermal acid extraction began. It successfully lit four light bulbs. Later, in 1911, the world's first commercial geothermal power plant was built there. It was the world's only industrial producer of geothermal electricity until New Zealand built a plant in 1958. In 2012, it produced some 594 megawatts. In 1960, Pacific Gas and Electric began operation of the first successful geothermal electric power plant in the United States at The Geysers in California. The original turbine lasted for more than 30 years and produced 11 MW net power. The binary cycle power plant was first demonstrated in 1967 in the USSR and later introduced to the US in 1981. This technology allows the generation of electricity from much lower temperature resources than previously. In 2006, a binary cycle plant in Chena Hot Springs, Alaska, came on-line, producing electricity from a record low fluid temperature of . Geothermal power upright=1.3|Installed geothermal energy capacity, 2019 Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 26 countries,Geothermal Energy Association. Geothermal Energy: International Market Update May 2010, p. 4-6. while geothermal heating is in use in 70 countries.Moomaw, W., P. Burgherr, G. Heath, M. Lenzen, J. Nyboer, A. Verbruggen, 2011: Annex II: Methodology. In IPCC: Special Report on Renewable Energy Sources and Climate Change Mitigation (ref. page 10) As of 2019, worldwide geothermal power capacity amounts to 15.4 gigawatts (GW), of which 23.86 percent or 3.68 GW are installed in the United States. International markets grew at an average annual rate of 5 percent over the three years to 2015, and global geothermal power capacity is expected to reach 14.5–17.6 GW by 2020. Based on current geologic knowledge and technology the GEA publicly discloses, the Geothermal Energy Association (GEA) estimates that only 6.9 percent of total global potential has been tapped so far, while the IPCC reported geothermal power potential to be in the range of 35 GW to 2 TW. Countries generating more than 15 percent of their electricity from geothermal sources include El Salvador, Kenya, the Philippines, Iceland, New Zealand, and Costa Rica. Geothermal power is considered to be a sustainable, renewable source of energy because the heat extraction is small compared with the Earth's heat content. The greenhouse gas emissions of geothermal electric stations are on average 45 grams of carbon dioxide per kilowatt-hour of electricity, or less than 5 percent of that of conventional coal-fired plants.Moomaw, W., P. Burgherr, G. Heath, M. Lenzen, J. Nyboer, A. Verbruggen, 2011: Annex II: Methodology. In IPCC: Special Report on Renewable Energy Sources and Climate Change Mitigation (ref. page 10) As a source of renewable energy for both power and heating, geothermal has the potential to meet 3-5\% of global demand by 2050. With economic incentives, it is estimated that by 2100 it will be possible to meet 10\% of global demand. + Direct use data 2015 Country Capacity (MW) 2015United States 17,415.91Philippines 3.30Indonesia 2.30Mexico 155.82 Italy 1,014.00New Zealand 487.45Iceland 2,040.00Japan 2,186.17Iran 81.50El Salvador 3.36Kenya 22.40 Costa Rica 1.00 Russia 308.20Turkey 2,886.30Papua-New Guinea 0.10Guatemala 2.31Portugal 35.20 China 17,870.00 France 2,346.90 Ethiopia 2.20Germany 2,848.60Austria 903.40Australia 16.09Thailand 128.51 + Installed geothermal electric capacity Country Capacity (MW) 2007 Capacity (MW) 2010 Capacity (MW) 2020 \% of national electricity production \% of global geothermal productionUnited States 2687308637140.3 29Philippines 1969.7190419182718Indonesia 992119721333.711Mexico 953958962.739Italy 810.58439441.58New Zealand 471.66281005106Iceland 421.2575755305Japan 535.25366030.15Iran 250250 El Salvador 204.2204n/a25Kenya 128.816796111.2Costa Rica 162.5166n/a14Nicaragua 87.488n/a10Russia 7982 Turkey 38821526 Papua-New Guinea 5656 Guatemala 5352 Portugal 2329 China 27.824 France 14.716 Ethiopia 7.37.3 Germany 8.46.6 Austria 1.11.4 Australia 0.21.1 Thailand 0.30.3 Total 9,981.9 10,959.7 15,608 Geothermal electric plants were traditionally built exclusively on the edges of tectonic plates where high-temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology enable enhanced geothermal systems over a much greater geographical range. Demonstration projects are operational in Landau-Pfalz, Germany, and Soultz-sous-Forêts, France, while an earlier effort in Basel, Switzerland, was shut down after it triggered earthquakes. Other demonstration projects are under construction in Australia, the United Kingdom, and the United States of America. Geothermal heating Sources with temperatures of 30–150 °C are used without conversion to electricity as district heating, greenhouses, fisheries, mineral recovery, industrial process heating and bathing in 75 countries. Home heating is the fastest-growing means of exploiting geothermal energy, with global annual growth rate of 30\% in 2005 and 20\% in 2012. Heating is cost-effective at many more sites than electricity generation. At natural hot springs or geysers, water can be piped directly into radiators. In the hot, dry ground, earth tubes or downhole heat exchangers can collect the heat. Iceland is the world leader in direct applications. Some 92.5\% of its homes are heated with geothermal energy, saving Iceland over $100 million annually in avoided oil imports. Reykjavík, Iceland has the world's biggest district heating system, often used to heat pathways and roads to hinder the accumulation of ice. Once known as the most polluted city in the world, it is now   one of the cleanest.
Revised:  More recent technological advances have dramatically reduced costs and thereby expanded the range and size of viable resource and in 2021 the U.S. Department of Energy estimates that geothermal energy from a power plant "built today" costs about $0.05/kWh. Worldwide, 13,900 megawatts (MW) of geothermal power was available in 2019. An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating, space heating, spas, industrial processes, desalination and agricultural applications as of 2010. Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, plate boundary movement and interest rates. Pilot programs like EWEB's customer opt in Green Power ProgramGreen Power . eweb.org show that customers would be willing to pay a little more for a renewable energy source like geothermal. About 100 thousand people are employed in the industry. The adjective geothermal originates from the Greek roots (), meaning Earth, and (), meaning hot. History The oldest known pool fed by a hot spring, built in the Qin dynasty in the 3rd century BCE Hot springs have been used for bathing at least since Paleolithic times. The oldest known spa is a stone pool on China's Lisan mountain built in the Qin Dynasty in the 3rd century BCE, at the same site where the Huaqing Chi palace was later built. In the first century CE, Romans conquered Aquae Sulis, now Bath, Somerset, England, and used the hot springs there to feed public baths and underfloor heating. The admission fees for these baths probably represent the first commercial use of geothermal power. The world's oldest geothermal district heating system in Chaudes-Aigues, France, has been operating since the 15th century. The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy. In 1892, America's first district heating system in Boise, Idaho was powered directly by geothermal energy, and was copied in Klamath Falls, Oregon in 1900. The first known building in the world to utilize geothermal energy as its primary heat source was the Hot Lake Hotel in Union County, Oregon, whose construction was completed in 1907. A deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the same time. Charlie Lieb developed the first downhole heat exchanger in 1930 to heat his house. Steam and hot water from geysers began heating homes in Iceland starting in 1943. Global geothermal electric capacity. Upper red line is installed capacity; lower green line is realized production. In the 20th century, demand for electricity led to the consideration of geothermal power as a generating source. Prince Piero Ginori Conti tested the first geothermal power generator on 4 July 1904, at the same Larderello dry steam field where geothermal acid extraction began. It successfully lit four light bulbs. Later, in 1911, the world's first commercial geothermal power plant was built there. It was the world's only industrial producer of geothermal electricity until New Zealand built a plant in 1958. In 2012, it produced some 594 megawatts. In 1960, Pacific Gas and Electric began operation of the first successful geothermal electric power plant in the United States at The Geysers in California. The original turbine lasted for more than 30 years and produced 11 MW net power. The binary cycle power plant was first demonstrated in 1967 in the USSR and later introduced to the US in 1981. This technology allows the generation of electricity from much lower temperature resources than previously. In 2006, a binary cycle plant in Chena Hot Springs, Alaska, came on-line, producing electricity from a record low fluid temperature of . Geothermal power upright=1.3|Installed geothermal energy capacity, 2019 Geothermal power is electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 26 countries,Geothermal Energy Association. Geothermal Energy: International Market Update May 2010, p. 4-6. while geothermal heating is in use in 70 countries.Moomaw, W., P. Burgherr, G. Heath, M. Lenzen, J. Nyboer, A. Verbruggen, 2011: Annex II: Methodology. In IPCC: Special Report on Renewable Energy Sources and Climate Change Mitigation (ref. page 10) As of 2019, worldwide geothermal power capacity amounts to 15.4 gigawatts (GW), of which 23.86 percent or 3.68 GW are installed in the United States. International markets grew at an average annual rate of 5 percent over the three years to 2015, and global geothermal power capacity is expected to reach 14.5–17.6 GW by 2020. Based on current geologic knowledge and technology the GEA publicly discloses, the Geothermal Energy Association (GEA) estimates that only 6.9 percent of total global potential has been tapped so far, while the IPCC reported geothermal power potential to be in the range of 35 GW to 2 TW. Countries generating more than 15 percent of their electricity from geothermal sources include El Salvador, Kenya, the Philippines, Iceland, New Zealand, and Costa Rica. Geothermal power is considered to be a sustainable, renewable source of energy because the heat extraction is small compared with the Earth's heat content. The greenhouse gas emissions of geothermal electric stations are on average 45 grams of carbon dioxide per kilowatt-hour of electricity, or less than 5 percent of that of conventional coal-fired plants.Moomaw, W., P. Burgherr, G. Heath, M. Lenzen, J. Nyboer, A. Verbruggen, 2011: Annex II: Methodology. In IPCC: Special Report on Renewable Energy Sources and Climate Change Mitigation (ref. page 10) As a source of renewable energy for both power and heating, geothermal has the potential to meet 3-5\% of global demand by 2050. With economic incentives, it is estimated that by 2100 it will be possible to meet 10\% of global demand. + Direct use data 2015 Country Capacity (MW) 2015United States 17,415.91Philippines 3.30Indonesia 2.30Mexico 155.82 Italy 1,014.00New Zealand 487.45Iceland 2,040.00Japan 2,186.17Iran 81.50El Salvador 3.36Kenya 22.40 Costa Rica 1.00 Russia 308.20Turkey 2,886.30Papua-New Guinea 0.10Guatemala 2.31Portugal 35.20 China 17,870.00 France 2,346.90 Ethiopia 2.20Germany 2,848.60Austria 903.40Australia 16.09Thailand 128.51 + Installed geothermal electric capacity Country Capacity (MW) 2007 Capacity (MW) 2010 Capacity (MW) 2020 \% of national electricity production \% of global geothermal productionUnited States 2687308637140.3 29Philippines 1969.7190419182718Indonesia 992119721333.711Mexico 953958962.739Italy 810.58439441.58New Zealand 471.66281005106Iceland 421.2575755305Japan 535.25366030.15Iran 250250 El Salvador 204.2204n/a25Kenya 128.816796111.2Costa Rica 162.5166n/a14Nicaragua 87.488n/a10Russia 7982 Turkey 38821526 Papua-New Guinea 5656 Guatemala 5352 Portugal 2329 China 27.824 France 14.716 Ethiopia 7.37.3 Germany 8.46.6 Austria 1.11.4 Australia 0.21.1 Thailand 0.30.3 Total 9,981.9 10,959.7 15,608 Geothermal electric plants were traditionally built exclusively on the edges of tectonic plates where high-temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology enable enhanced geothermal systems over a much greater geographical range. Demonstration projects are operational in Landau-Pfalz, Germany, and Soultz-sous-Forêts, France, while an earlier effort in Basel, Switzerland, was shut down after it triggered earthquakes. Other demonstration projects are under construction in Australia, the United Kingdom, and the United States of America. Geothermal heating Geothermal heating is the direct use of geothermal energy for some heating applications. Humans have taken advantage of geothermal heat this way since the Paleolithic era. Approximately seventy countries made direct use of a total of 270 PJ of geothermal heating in 2004. As of 2007, 28 GW of geothermal heating capacity is installed around the world, satisfying 0.07\% of global primary energy consumption. Thermal efficiency is high since no energy conversion is needed, but capacity factors tend to be low (around 20\%) since the heat is mostly needed in the winter. Geothermal energy originates from the heat retained within the Earth since the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface. Most high temperature geothermal heat is harvested in regions close to tectonic plate boundaries where volcanic activity rises close to the surface of the Earth. In these areas, ground and groundwater can be found with temperatures higher than the target temperature of the application. However, even cold ground contains heat, below the undisturbed ground temperature is consistently at the Mean Annual Air TemperatureMean Annual Air Temperature and it may be extracted with a ground source heat pump. Types Geothermal energy comes in either vapor-dominated or liquid-dominated forms. Larderello and The Geysers are vapor-dominated. Vapor-dominated sites offer temperatures from 240 to 300 °C that produce superheated steam. Liquid-dominated plants Liquid-dominated reservoirs (LDRs) are more common with temperatures greater than and are found near young volcanoes surrounding the Pacific Ocean and in rift zones and hot spots. Flash plants are the common way to generate electricity from these sources. Pumps are generally not required, powered instead when the water turns to steam. Most wells generate 2–10 MW of electricity. Steam is separated from a liquid via cyclone separators, while the liquid is returned to the reservoir for reheating/reuse. As of 2013, the largest liquid system is Cerro Prieto in Mexico, which generates 750 MW of electricity from temperatures reaching . The Salton Sea field in Southern California offers the potential of generating 2000 MW of electricity. Lower-temperature LDRs (120–200 °C) require pumping. They are common in extensional terrains, where heating takes place via deep circulation along faults, such as in the Western US and Turkey. Water passes through a heat exchanger in a Rankine cycle binary plant. The water vaporizes an organic working fluid that drives a turbine. These binary plants originated in the Soviet Union in the late 1960s and predominate in new US plants. Binary plants have no emissions.Low-Temperature and Co-produced Geothermal Resources. U.S. Department of Energy. Enhanced geothermal systems Enhanced geothermal systems (EGS) actively inject water into wells to be heated and pumped back out. The water is injected under high pressure to expand existing rock fissures to enable the water to freely flow in and out. The technique was adapted from oil and gas extraction techniques. However, the geologic formations are deeper and no toxic chemicals are used, reducing the possibility of environmental damage. Drillers can employ directional drilling to expand the size of the reservoir. Small-scale EGS have been installed in the Rhine Graben at Soultz-sous-Forêts in France and at Landau and Insheim in Germany. Economics Geothermal power requires no fuel (except for pumps), and is therefore immune to fuel cost fluctuations. However, capital costs are significant. Drilling accounts for over half the costs, and exploration of deep resources entails significant risks. A typical well doublet (extraction and injection wells) in Nevada can support 4.5 megawatts (MW) and costs about $10 million to drill, with a 20\% failure rate. one of the cleanest.
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