Geothermal electricity
Encyclopedia
Geothermal electricity is electricity generated
from geothermal energy.
Technologies in use include dry steam power plants, flash steam power plants and binary cycle power plants. Geothermal electricity generation is currently used in 24 countries, while geothermal heating
is in use in 70 countries.
Estimates of the electricity generating potential of geothermal energy vary from 35 to 2,000 GW. Current worldwide installed capacity is 10,715 megawatts (MW), with the largest capacity in the United States
(3,086 MW), Philippines
, and Indonesia
.
Geothermal power is considered to be sustainable
because the heat extraction is small compared with the Earth's heat content. The emission intensity
of existing geothermal electric plants is on average 122 kg of per megawatt-hour (MW·h) of electricity, about one-eighth of a conventional coal-fired plant.
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 in Larderello
, Italy. It successfully lit four light bulbs. Later, in 1911, the world's first commercial geothermal power plant was built there. Experimental generators were built in Beppu, Japan and the Geysers
, California, in the 1920s, but Italy was the world's only industrial producer of geothermal electricity until 1958.
In 1958, New Zealand became the second major industrial producer of geothermal electricity when its Wairakei station
was commissioned. Wairakei was the first plant to use flash steam technology.
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 Russia and later introduced to the USA in 1981, following the 1970s energy crisis
and significant changes in regulatory policies. This technology allows the use of much lower temperature resources than were previously recoverable. In 2006, a binary cycle plant in Chena Hot Springs, Alaska
, came on-line, producing electricity from a record low fluid temperature of 57°C (135°F).
Geothermal electric plants have until recently been built exclusively where high temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology may 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.
The thermal efficiency
of geothermal electric plants is low, around 10-23%, because geothermal fluids are at a low temperature compared with steam from boilers. By the laws of thermodynamics
this low temperature limits the efficiency of heat engines in extracting useful energy during the generation of electricity. Exhaust heat is wasted, unless it can be used directly and locally, for example in greenhouses, timber mills, and district heating. The efficiency of the system does not affect operational costs as it would for a coal or other fossil fuel plant, but it does factor into the viability of the plant. In order to produce more energy than the pumps consume, electricity generation requires high temperature geothermal fields and specialized heat cycles. Because geothermal power does not rely on variable sources of energy, unlike, for example, wind or solar, its capacity factor
can be quite large – up to 96% has been demonstrated. The global average was 73% in 2005.
, water or other) to release the heat underneath.
Electricity generation requires high temperature resources that can only come from deep underground. The heat must be carried to the surface by fluid circulation, either through magma conduits, hot springs
, hydrothermal circulation
, oil well
s, drilled water wells, or a combination of these. This circulation sometimes exists naturally where the crust is thin: magma conduits bring heat close to the surface, and hot springs bring the heat to the surface. If no hot spring is available, a well must be drilled into a hot aquifer
. Away from tectonic plate boundaries the geothermal gradient
is 25-30°C per kilometre (km) of depth in most of the world, and wells would have to be several kilometres deep to permit electricity generation. The quantity and quality of recoverable resources improves with drilling depth and proximity to tectonic plate boundaries.
In ground that is hot but dry, or where water pressure is inadequate, injected fluid can stimulate production. Developers bore two holes into a candidate site, and fracture the rock between them with explosives or high pressure water. Then they pump water or liquefied carbon dioxide down one borehole, and it comes up the other borehole as a gas. This approach is called hot dry rock geothermal energy in Europe, or enhanced geothermal systems
in North America. Much greater potential may be available from this approach than from conventional tapping of natural aquifers.
Estimates of the electricity generating potential of geothermal energy vary from 35 to 2000 GW depending on the scale of investments. This does not include non-electric heat recovered by co-generation, geothermal heat pumps and other direct use. A 2006 report by the Massachusetts Institute of Technology (MIT), that included the potential of enhanced geothermal systems, estimated that investing 1 billion US dollars in research and development over 15 years would allow the creation of 100 GW of electrical generating capacity by 2050 in the United States alone. The MIT report estimated that over 200 zettajoules (ZJ) would be extractable, with the potential to increase this to over 2,000 ZJ with technology improvements - sufficient to provide all the world's present energy needs for several millennia
.
At present, geothermal wells are rarely more than 3 kilometres (2 mi) deep. Upper estimates of geothermal resources assume wells as deep as 10 kilometres (6 mi). Drilling at this depth is now possible in the petroleum industry, although it is an expensive process. The deepest research well in the world, the Kola superdeep borehole
, is 12 kilometres (7 mi) deep. This record has recently been imitated by commercial oil wells, such as Exxon
's Z-12 well in the Chayvo field, Sakhalin
. Wells drilled to depths greater than 4 kilometres (2 mi) generally incur drilling costs in the tens of millions of dollars. The technological challenges are to drill wide bores at low cost and to break larger volumes of rock.
Geothermal power is considered to be sustainable
because the heat extraction is small compared to the Earth's heat content, but extraction must still be monitored to avoid local depletion. Although geothermal sites are capable of providing heat for many decades, individual wells may cool down or run out of water. The three oldest sites, at Larderello, Wairakei, and the Geysers have all reduced production from their peaks. It is not clear whether these plants extracted energy faster than it was replenished from greater depths, or whether the aquifers supplying them are being depleted. If production is reduced, and water is reinjected, these wells could theoretically recover their full potential. Such mitigation strategies have already been implemented at some sites. The long-term sustainability of geothermal energy has been demonstrated at the Lardarello field in Italy since 1913, at the Wairakei field in New Zealand since 1958, and at The Geysers field in California since 1960.
s - heat from a fuel source (in geothermal's case, the earth's core) is used to heat water or another working fluid. The working fluid is then used to turn a turbine of a generator, thereby producing electricity. The fluid is then cooled and returned to the heat source.
s are used. The thermal efficiency of this type plant is typically about 10-13%.
In 2010, the United States
led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is located at The Geysers
, a geothermal field in California
. The Philippines follows the US as the second highest producer of geothermal power in the world, with 1,904 MW of capacity online; geothermal power makes up approximately 18% of the country's electricity generation.
January 2011: Al Gore
said in The Climate Project Asia Pacific Summit that Indonesia could become a super power country in electricity production from geothermal energy.
, a geothermal field in California
, United States
. As of 2004, five countries (El Salvador
, Kenya
, the Philippines
, Iceland
, and Costa Rica
) generate more than 15% of their electricity from geothermal sources.
Naknek Electric Association (NEA) is going to make an exploration well near King Salmon, in Southwest Alaska
. It could cut the cost of electricity production by 71 percent and the planned power is 25 megawatts.
Geothermal electricity is generated in the 24 countries listed in the table below. During 2005, contracts were placed for an additional 500 MW of electrical capacity in the United States, while there were also plants under construction in 11 other countries. Enhanced geothermal systems that are several kilometres in depth are operational in France and Germany and are being developed or evaluated in at least four other countries.
Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide
, hydrogen sulfide
, methane
, and ammonia
. These pollutants contribute to global warming
, acid rain
, and noxious smells if released. Existing geothermal electric plants emit an average of 122 kg of per megawatt-hour (MW·h) of electricity, a small fraction of the emission intensity
of conventional fossil fuel plants. Plants that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust. Geothermal plants could theoretically inject these gases back into the earth, as a form of carbon capture and storage
.
In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic chemicals, such as mercury
, arsenic
, boron
, antimony
, and salt. These chemicals come out of solution as the water cools, and can cause environmental damage if released. The modern practice of injecting geothermal fluids back into the Earth to stimulate production has the side benefit of reducing this environmental risk.
Plant construction can adversely affect land stability. Subsidence
has occurred in the Wairakei field in New Zealand. Enhanced geothermal systems
can trigger earthquake
s as part of hydraulic fracturing
. The project in Basel
, Switzerland
was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter Scale occurred over the first 6 days of water injection. The risk of geothermal drilling leading to uplift
has been experienced in Staufen im Breisgau.
Geothermal has minimal land and freshwater requirements. Geothermal plants use 404 square meters per GWh versus 3,632 and 1,335 square kilometres for coal facilities and wind farms respectively. They use 20 litres of freshwater per MW·h versus over 1000 litres per MW·h for nuclear, coal, or oil.
In total, electrical plant construction and well drilling cost about 2-5 million € per MW of electrical capacity, while the levelised energy cost is 0.04-0.10 € per kW·h. Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4 million per MW and levelized costs above $0.054 per kW·h in 2007.
Geothermal power is highly scalable: a small power plant can supply a rural village, though capital can be high.
Chevron Corporation
is the world's largest private producer of geothermal electricity. The most developed geothermal field is the Geysers in California. In 2008, this field supported 15 plants, all owned by Calpine
, with a total generating capacity of 725 MW.
Electricity generation
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...
from geothermal energy.
Technologies in use include dry steam power plants, flash steam power plants and binary cycle power plants. Geothermal electricity generation is currently used in 24 countries, while geothermal heating
Geothermal heating
Geothermal heating is the direct use of geothermal energy for 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...
is in use in 70 countries.
Estimates of the electricity generating potential of geothermal energy vary from 35 to 2,000 GW. Current worldwide installed capacity is 10,715 megawatts (MW), with the largest capacity in the United States
Geothermal energy in the United States
Geothermal energy in the United States continues to be an area of considerable activity. In 2010, the United States led the world in geothermal electricity production with 3,086 megawatts of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is...
(3,086 MW), Philippines
Geothermal power in the Philippines
The Geothermal Education Office and a 1980 article entitled "The Philippines geothermal success story" by Rudolph J. Birsic published in the journal Geothermal Energy note the remarkable geothermal resources of the Philippines...
, and Indonesia
Geothermal power in Indonesia
Geothermal power in Indonesia is an increasingly significant source of renewable energy. As a result of its volcanic geology, Indonesia has 40% of the world's potential geothermal resources, estimated at 28,000 megawatts ....
.
Geothermal power is considered to be sustainable
Sustainability
Sustainability is the capacity to endure. For humans, sustainability is the long-term maintenance of well being, which has environmental, economic, and social dimensions, and encompasses the concept of union, an interdependent relationship and mutual responsible position with all living and non...
because the heat extraction is small compared with the Earth's heat content. The emission intensity
Emission intensity
An emission intensity is the average emission rate of a given pollutant from a given source relative to the intensity of a specific activity; for example grams of carbon dioxide released per megajoule of energy produced, or the ratio of greenhouse gas emissions produced to GDP...
of existing geothermal electric plants is on average 122 kg of per megawatt-hour (MW·h) of electricity, about one-eighth of a conventional coal-fired plant.
History and development
Larderello
Larderello is a frazione of the comune of Pomarance, in Tuscany in central Italy. It is a geologically active area, renowned for its geothermal productivity.- Geography :...
, Italy. It successfully lit four light bulbs. Later, in 1911, the world's first commercial geothermal power plant was built there. Experimental generators were built in Beppu, Japan and the Geysers
The Geysers
The Geysers is a complex of 22 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains north of San Francisco, California.The largest in the world, the Geysers has...
, California, in the 1920s, but Italy was the world's only industrial producer of geothermal electricity until 1958.
In 1958, New Zealand became the second major industrial producer of geothermal electricity when its Wairakei station
Wairakei Power Station
The Wairakei Power Station is a geothermal power station near the Wairakei Geothermal Field in New Zealand. Wairakei lies in the Taupo Volcanic Zone.- History :...
was commissioned. Wairakei was the first plant to use flash steam technology.
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 Russia and later introduced to the USA in 1981, following the 1970s energy crisis
1970s energy crisis
The 1970s energy crisis was a period in which the major industrial countries of the world, particularly the United States, faced substantial shortages, both perceived and real, of petroleum...
and significant changes in regulatory policies. This technology allows the use of much lower temperature resources than were previously recoverable. In 2006, a binary cycle plant in Chena Hot Springs, Alaska
Chena Hot Springs, Alaska
Chena Hot Springs is a hot spring, resort, and community in the Fairbanks North Star Borough, Alaska, United States, 56.5 miles northeast of Fairbanks near the Chena River State Recreation Area...
, came on-line, producing electricity from a record low fluid temperature of 57°C (135°F).
Geothermal electric plants have until recently been built exclusively where high temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology may enable enhanced geothermal systems
Enhanced geothermal systems
Enhanced Geothermal System is a new type of geothermal power technology that does not require natural convective hydrothermal resources. Until recently, geothermal power systems have exploited only resources where naturally occurring heat, water, and rock permeability are sufficient to allow...
over a much greater geographical range. Demonstration projects are operational in Landau-Pfalz, Germany, and Soultz-sous-Forêts
Soultz-sous-Forêts
Soultz-sous-Forêts is a commune in the Bas-Rhin department in Alsace in north-eastern France.It is the site of the European Hot Dry Rocks energy research project.-References:*...
, France, while an earlier effort in Basel
Basel
Basel or Basle In the national languages of Switzerland the city is also known as Bâle , Basilea and Basilea is Switzerland's third most populous city with about 166,000 inhabitants. Located where the Swiss, French and German borders meet, Basel also has suburbs in France and Germany...
, Switzerland was shut down after it triggered earthquakes. Other demonstration projects are under construction in Australia, the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and the United States of America.
The thermal efficiency
Thermal efficiency
In thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...
of geothermal electric plants is low, around 10-23%, because geothermal fluids are at a low temperature compared with steam from boilers. By the laws of thermodynamics
Thermodynamics
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...
this low temperature limits the efficiency of heat engines in extracting useful energy during the generation of electricity. Exhaust heat is wasted, unless it can be used directly and locally, for example in greenhouses, timber mills, and district heating. The efficiency of the system does not affect operational costs as it would for a coal or other fossil fuel plant, but it does factor into the viability of the plant. In order to produce more energy than the pumps consume, electricity generation requires high temperature geothermal fields and specialized heat cycles. Because geothermal power does not rely on variable sources of energy, unlike, for example, wind or solar, its capacity factor
Capacity factor
The net capacity factor or load factor of a power plant is the ratio of the actual output of a power plant over a period of time and its potential output if it had operated at full nameplate capacity the entire time...
can be quite large – up to 96% has been demonstrated. The global average was 73% in 2005.
Resources
The earth’s heat content is 1031 joules. This heat naturally flows to the surface by conduction at a rate of 44.2 terawatts, (TW,) and is replenished by radioactive decay at a rate of 30 TW. These power rates are more than double humanity’s current energy consumption from primary sources, but most of this power is too diffuse (approximately 0.1 W/m2 on average) to be recoverable. The Earth's crust effectively acts as a thick insulating blanket which must be pierced by fluid conduits (of magmaMagma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
, water or other) to release the heat underneath.
Electricity generation requires high temperature resources that can only come from deep underground. The heat must be carried to the surface by fluid circulation, either through magma conduits, hot springs
Hot Springs
Hot Springs may refer to:* Hot Springs, Arkansas** Hot Springs National Park, Arkansas*Hot Springs, California**Hot Springs, Lassen County, California**Hot Springs, Modoc County, California**Hot Springs, Placer County, California...
, hydrothermal circulation
Hydrothermal circulation
Hydrothermal circulation in its most general sense is the circulation of hot water; 'hydros' in the Greek meaning water and 'thermos' meaning heat. Hydrothermal circulation occurs most often in the vicinity of sources of heat within the Earth's crust...
, oil well
Oil well
An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...
s, drilled water wells, or a combination of these. This circulation sometimes exists naturally where the crust is thin: magma conduits bring heat close to the surface, and hot springs bring the heat to the surface. If no hot spring is available, a well must be drilled into a hot aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
. Away from tectonic plate boundaries the geothermal gradient
Geothermal gradient
Geothermal gradient is the rate of increasing temperature with respect to increasing depth in the Earth's interior. Away from tectonic plate boundaries, it is 25–30°C per km of depth in most of the world. Strictly speaking, geo-thermal necessarily refers to the Earth but the concept may be applied...
is 25-30°C per kilometre (km) of depth in most of the world, and wells would have to be several kilometres deep to permit electricity generation. The quantity and quality of recoverable resources improves with drilling depth and proximity to tectonic plate boundaries.
In ground that is hot but dry, or where water pressure is inadequate, injected fluid can stimulate production. Developers bore two holes into a candidate site, and fracture the rock between them with explosives or high pressure water. Then they pump water or liquefied carbon dioxide down one borehole, and it comes up the other borehole as a gas. This approach is called hot dry rock geothermal energy in Europe, or enhanced geothermal systems
Enhanced geothermal systems
Enhanced Geothermal System is a new type of geothermal power technology that does not require natural convective hydrothermal resources. Until recently, geothermal power systems have exploited only resources where naturally occurring heat, water, and rock permeability are sufficient to allow...
in North America. Much greater potential may be available from this approach than from conventional tapping of natural aquifers.
Estimates of the electricity generating potential of geothermal energy vary from 35 to 2000 GW depending on the scale of investments. This does not include non-electric heat recovered by co-generation, geothermal heat pumps and other direct use. A 2006 report by the Massachusetts Institute of Technology (MIT), that included the potential of enhanced geothermal systems, estimated that investing 1 billion US dollars in research and development over 15 years would allow the creation of 100 GW of electrical generating capacity by 2050 in the United States alone. The MIT report estimated that over 200 zettajoules (ZJ) would be extractable, with the potential to increase this to over 2,000 ZJ with technology improvements - sufficient to provide all the world's present energy needs for several millennia
Millennium
A millennium is a period of time equal to one thousand years —from the Latin phrase , thousand, and , year—often but not necessarily related numerically to a particular dating system....
.
At present, geothermal wells are rarely more than 3 kilometres (2 mi) deep. Upper estimates of geothermal resources assume wells as deep as 10 kilometres (6 mi). Drilling at this depth is now possible in the petroleum industry, although it is an expensive process. The deepest research well in the world, the Kola superdeep borehole
Kola Superdeep Borehole
The Kola Superdeep Borehole is the result of a scientific drilling project of the Soviet Union in Kola Peninsula. The project attempted to drill as deep as possible into the Earth's crust. Drilling began on 24 May 1970 using the Uralmash-4E, and later the Uralmash-15000 series drilling rig. A...
, is 12 kilometres (7 mi) deep. This record has recently been imitated by commercial oil wells, such as Exxon
Exxon
Exxon is a chain of gas stations as well as a brand of motor fuel and related products by ExxonMobil. From 1972 to 1999, Exxon was the corporate name of the company previously known as Standard Oil Company of New Jersey or Jersey Standard....
's Z-12 well in the Chayvo field, Sakhalin
Sakhalin-I
The Sakhalin-I project, a sister project to Sakhalin-II, is a consortium to locate and produce oil and gas on Sakhalin Island and immediately offshore, in the Okhotsk Sea, from three fields: Chayvo, Odoptu, and Arkutun-Dagi....
. Wells drilled to depths greater than 4 kilometres (2 mi) generally incur drilling costs in the tens of millions of dollars. The technological challenges are to drill wide bores at low cost and to break larger volumes of rock.
Geothermal power is considered to be sustainable
Sustainability
Sustainability is the capacity to endure. For humans, sustainability is the long-term maintenance of well being, which has environmental, economic, and social dimensions, and encompasses the concept of union, an interdependent relationship and mutual responsible position with all living and non...
because the heat extraction is small compared to the Earth's heat content, but extraction must still be monitored to avoid local depletion. Although geothermal sites are capable of providing heat for many decades, individual wells may cool down or run out of water. The three oldest sites, at Larderello, Wairakei, and the Geysers have all reduced production from their peaks. It is not clear whether these plants extracted energy faster than it was replenished from greater depths, or whether the aquifers supplying them are being depleted. If production is reduced, and water is reinjected, these wells could theoretically recover their full potential. Such mitigation strategies have already been implemented at some sites. The long-term sustainability of geothermal energy has been demonstrated at the Lardarello field in Italy since 1913, at the Wairakei field in New Zealand since 1958, and at The Geysers field in California since 1960.
Power station types
Geothermal power stations are not dissimilar to other steam turbine thermal power stationThermal power station
A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this...
s - heat from a fuel source (in geothermal's case, the earth's core) is used to heat water or another working fluid. The working fluid is then used to turn a turbine of a generator, thereby producing electricity. The fluid is then cooled and returned to the heat source.
Dry steam power plants
Dry steam plants are the simplest and oldest design. They directly use geothermal steam of 150°C or greater to turn turbines.Flash steam power plants
Flash steam plants pull deep, high-pressure hot water into lower-pressure tanks and use the resulting flashed steam to drive turbines. They require fluid temperatures of at least 180°C, usually more. This is the most common type of plant in operation today.Binary cycle power plants
Binary cycle power plants are the most recent development, and can accept fluid temperatures as low as 57°C. The moderately hot geothermal water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to flash vaporize, which then drives the turbines. This is the most common type of geothermal electricity plant being constructed today. Both Organic Rankine and Kalina cycleKalina cycle
The Kalina cycle is a thermodynamic process for converting thermal energy into usable mechanical power.It uses a solution of 2 fluids with different boiling points for its working fluid. Since the solution boils over a range of temperatures as in distillation, more of the heat can be extracted...
s are used. The thermal efficiency of this type plant is typically about 10-13%.
Worldwide production
The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity in 2010. This represents a 20% increase in geothermal power online capacity since 2005. IGA projects this will grow to 18,500 MW by 2015, due to the large number of projects presently under consideration, often in areas previously assumed to have little exploitable resource.In 2010, the United States
Geothermal energy in the United States
Geothermal energy in the United States continues to be an area of considerable activity. In 2010, the United States led the world in geothermal electricity production with 3,086 megawatts of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is...
led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is located at The Geysers
The Geysers
The Geysers is a complex of 22 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains north of San Francisco, California.The largest in the world, the Geysers has...
, a geothermal field in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. The Philippines follows the US as the second highest producer of geothermal power in the world, with 1,904 MW of capacity online; geothermal power makes up approximately 18% of the country's electricity generation.
January 2011: Al Gore
Al Gore
Albert Arnold "Al" Gore, Jr. served as the 45th Vice President of the United States , under President Bill Clinton. He was the Democratic Party's nominee for President in the 2000 U.S. presidential election....
said in The Climate Project Asia Pacific Summit that Indonesia could become a super power country in electricity production from geothermal energy.
Utility-grade plants
The largest group of geothermal power plants in the world is located at The GeysersThe Geysers
The Geysers is a complex of 22 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains north of San Francisco, California.The largest in the world, the Geysers has...
, a geothermal field in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, United States
Geothermal energy in the United States
Geothermal energy in the United States continues to be an area of considerable activity. In 2010, the United States led the world in geothermal electricity production with 3,086 megawatts of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is...
. As of 2004, five countries (El Salvador
Geothermal power in El Salvador
Geothermal power in El Salvador represents 25% of its total electricity production. El Salvador is one of the top ten geothermal energy producers in the world. Since 1975, the Ahuachapán geothermal field has been in continuous and successful commercial operation. Since 1992, the Berlin geothermal...
, Kenya
Geothermal power in Kenya
Geothermal power is very cost-effective in the Rift area of Kenya, East Africa. Kenya was the first African country to build geothermal energy sources. Kenya Electricity Generating Company has built two plants, Olkaria I and Olkaria II , with a third private plant Olkaria III...
, the Philippines
Geothermal power in the Philippines
The Geothermal Education Office and a 1980 article entitled "The Philippines geothermal success story" by Rudolph J. Birsic published in the journal Geothermal Energy note the remarkable geothermal resources of the Philippines...
, Iceland
Geothermal power in Iceland
Due to the special geological location of Iceland, the high concentration of volcanoes in the area is often an advantage in the generation of geothermal energy, the heating and production of electricity...
, and Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
) generate more than 15% of their electricity from geothermal sources.
Naknek Electric Association (NEA) is going to make an exploration well near King Salmon, in Southwest Alaska
Southwest Alaska
Southwest Alaska is a region of the U.S. state of Alaska. The area is not exactly defined by any governmental administrative region; nor does it always have a clear geographic boundary.-Geography:...
. It could cut the cost of electricity production by 71 percent and the planned power is 25 megawatts.
Geothermal electricity is generated in the 24 countries listed in the table below. During 2005, contracts were placed for an additional 500 MW of electrical capacity in the United States, while there were also plants under construction in 11 other countries. Enhanced geothermal systems that are several kilometres in depth are operational in France and Germany and are being developed or evaluated in at least four other countries.
| Country | Capacity (MW) 2007 |
Capacity (MW) 2010 |
percentage of national production |
|---|---|---|---|
| USA Geothermal energy in the United States Geothermal energy in the United States continues to be an area of considerable activity. In 2010, the United States led the world in geothermal electricity production with 3,086 megawatts of installed capacity from 77 power plants; the largest group of geothermal power plants in the world is... |
2687 | 3086 | 0.3% |
| Philippines Geothermal power in the Philippines The Geothermal Education Office and a 1980 article entitled "The Philippines geothermal success story" by Rudolph J. Birsic published in the journal Geothermal Energy note the remarkable geothermal resources of the Philippines... |
1969.7 | 1904 | 27% |
| Indonesia Geothermal power in Indonesia Geothermal power in Indonesia is an increasingly significant source of renewable energy. As a result of its volcanic geology, Indonesia has 40% of the world's potential geothermal resources, estimated at 28,000 megawatts .... |
992 | 1197 | 3.7% |
| Mexico | 953 | 958 | 3% |
| Italy | 810.5 | 843 | 1.5% |
| New Zealand Geothermal power in New Zealand Geothermal power in New Zealand is a small but significant part of the energy generation capacity of the country, providing approximately 10% of the country's electricity with installed capacity of over 700 MW... |
471.6 | 628 | 10% |
| Iceland Geothermal power in Iceland Due to the special geological location of Iceland, the high concentration of volcanoes in the area is often an advantage in the generation of geothermal energy, the heating and production of electricity... |
421.2 | 575 | 30% |
| Japan Geothermal power in Japan Japan has favorable sites for geothermal power because of its proximity to the Izu-Bonin-Mariana Arc. In 2007, Japan had 535.2 MW of installed electric generating capacity, about 5% of the world total.... |
535.2 | 536 | 0.1% |
| El Salvador | 204.4 | 204 | 25% |
| Kenya Geothermal power in Kenya Geothermal power is very cost-effective in the Rift area of Kenya, East Africa. Kenya was the first African country to build geothermal energy sources. Kenya Electricity Generating Company has built two plants, Olkaria I and Olkaria II , with a third private plant Olkaria III... |
128.8 | 167 | 11.2% |
| Costa Rica | 162.5 | 166 | 14% |
| Turkey Geothermal power in Turkey In 2010 the installed geothermal electricity generation capacity was 100 MWe while direct use installations were approximately 795 MWt.As of 2005, Turkey had the 5th highest direct usage and capacity of geothermal energy in the world. Turkey's capacity as of 2005 is 1495 MWt with a usage of... |
38 | 94 | 0.3% |
| Nicaragua | 87.4 | 88 | 10% |
| Russia Geothermal power in Russia Russia demonstrated the first single-flash binary cycle power plant at Pauzhetka in 1967 . New two geothermal plants on the north slope of Mutnovsky volcano in Kamchatka, presumably supplying power to Petropavlovsk-Kamchatsky. Another small plants are on Kuril Islands — 1,8 and 2,5 MWe... |
79 | 82 | |
| Papua-New Guinea | 56 | 56 | |
| Guatemala | 53 | 52 | |
| Portugal Geothermal power in Portugal Portugal's main investment into this type of energy is in the Azores. While electricity is only produced on São Miguel, Azores, direct-use applications are also at Chaves in northern Portugal, at S... |
23 | 29 | |
| China Geothermal power in China -History:Geothermal energy exploitation in China started approximately around 1970. In the socialist planned economy geothermal exploration was handled by national bodies with public investments. Drilled productive wells were transferred free of charge to the final user... |
27.8 | 24 | |
| France | 14.7 | 16 | |
| Ethiopia | 7.3 | 7.3 | |
| Germany Geothermal power in Germany Electricity from geothermal sources is expected to grow in Germany mainly because a law that benefits the production of geothermal electricity and guarantees a feed-in tariff. Less than 0.4 percent of Germany's total primary energy supply came from geothermal sources in 2004... |
8.4 | 6.6 | |
| Austria | 1.1 | 1.4 | |
| Australia | 0.2 | 1.1 | |
| Thailand | 0.3 | 0.3 | |
| TOTAL | 9,731.9 | 10,709.7 | |
Environmental impact
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
, methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
, and ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
. These pollutants contribute to global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
, acid rain
Acid rain
Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions . It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen...
, and noxious smells if released. Existing geothermal electric plants emit an average of 122 kg of per megawatt-hour (MW·h) of electricity, a small fraction of the emission intensity
Emission intensity
An emission intensity is the average emission rate of a given pollutant from a given source relative to the intensity of a specific activity; for example grams of carbon dioxide released per megajoule of energy produced, or the ratio of greenhouse gas emissions produced to GDP...
of conventional fossil fuel plants. Plants that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust. Geothermal plants could theoretically inject these gases back into the earth, as a form of carbon capture and storage
Carbon capture and storage
Carbon capture and storage , alternatively referred to as carbon capture and sequestration, is a technology to prevent large quantities of from being released into the atmosphere from the use of fossil fuel in power generation and other industries. It is often regarded as a means of mitigating...
.
In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic chemicals, such as mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
, arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
, antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
, and salt. These chemicals come out of solution as the water cools, and can cause environmental damage if released. The modern practice of injecting geothermal fluids back into the Earth to stimulate production has the side benefit of reducing this environmental risk.
Plant construction can adversely affect land stability. Subsidence
Subsidence
Subsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is uplift, which results in an increase in elevation...
has occurred in the Wairakei field in New Zealand. Enhanced geothermal systems
Enhanced geothermal systems
Enhanced Geothermal System is a new type of geothermal power technology that does not require natural convective hydrothermal resources. Until recently, geothermal power systems have exploited only resources where naturally occurring heat, water, and rock permeability are sufficient to allow...
can trigger earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
s as part of hydraulic fracturing
Hydraulic fracturing
Considerable controversy surrounds the current implementation of hydraulic fracturing technology in the United States. Hydraulic fracturing, or fracking, is the process of utilizing pressurized water, or some other liquid, to fracture rock layers and release petroleum, natural gas, or other...
. The project in Basel
Basel
Basel or Basle In the national languages of Switzerland the city is also known as Bâle , Basilea and Basilea is Switzerland's third most populous city with about 166,000 inhabitants. Located where the Swiss, French and German borders meet, Basel also has suburbs in France and Germany...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter Scale occurred over the first 6 days of water injection. The risk of geothermal drilling leading to uplift
Tectonic uplift
Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...
has been experienced in Staufen im Breisgau.
Geothermal has minimal land and freshwater requirements. Geothermal plants use 404 square meters per GWh versus 3,632 and 1,335 square kilometres for coal facilities and wind farms respectively. They use 20 litres of freshwater per MW·h versus over 1000 litres per MW·h for nuclear, coal, or oil.
Economics
Geothermal power requires no fuel, it is therefore immune to fuel cost fluctuations. However, capital costs tend to be high. Drilling accounts for over half the costs, and exploration of deep resources entails significant risks. A typical well doublet in Nevada can support 4.5 megawatt (MW) of electricity generation and costs about $10 million to drill, with a 20% failure rate.In total, electrical plant construction and well drilling cost about 2-5 million € per MW of electrical capacity, while the levelised energy cost is 0.04-0.10 € per kW·h. Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4 million per MW and levelized costs above $0.054 per kW·h in 2007.
Geothermal power is highly scalable: a small power plant can supply a rural village, though capital can be high.
Chevron Corporation
Chevron Corporation
Chevron Corporation is an American multinational energy corporation headquartered in San Ramon, California, United States and active in more than 180 countries. It is engaged in every aspect of the oil, gas, and geothermal energy industries, including exploration and production; refining,...
is the world's largest private producer of geothermal electricity. The most developed geothermal field is the Geysers in California. In 2008, this field supported 15 plants, all owned by Calpine
Calpine
Calpine Corporation is a Fortune 500 power company founded in 1984 in San Jose, California.Calpine's headquarters were permanently moved from San Jose to Houston, Texas in 2009. The company's stock was traded on the New York Stock Exchange under the symbol CPN until it was delisted on December 5,...
, with a total generating capacity of 725 MW.