Geothermal energy

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials (in currently uncertain[1] but possibly roughly equal[2] proportions). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots γη (ge), meaning earth, and θερμος (thermos), meaning hot.

Earth's internal heat is thermal energy generated from radioactive decay and continual heat loss from Earth's formation.[3] Temperatures at the core–mantle boundary may reach over 4000 °C (7,200 °F).[4] The high temperature and pressure in Earth's interior cause some rock to melt and solid mantle to behave plastically, resulting in portions of the mantle convecting upward since it is lighter than the surrounding rock. Rock and water is heated in the crust, sometimes up to 370 °C (700 °F).[5]

With water from hot springs, geothermal energy has been used for bathing since Paleolithic times and for space heating since ancient Roman times, but it is now better known for electricity generation. Worldwide, 11,700 megawatts (MW) of geothermal power was available in 2013.[6] 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.[7]

Geothermal power is cost-effective, reliable, sustainable, and environmentally friendly,[8] but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels.

The Earth's geothermal resources are theoretically more than adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited. Drilling and exploration for deep resources is very expensive. 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 Program[9] show that customers would be willing to pay a little more for a renewable energy source like geothermal. But as a result of government assisted research and industry experience, the cost of generating geothermal power has decreased by 25% over the past two decades.[10] In 2001, geothermal energy costs between two and ten US cents per kWh.[11]

History

Oldest geothermal
The oldest known pool fed by a hot spring, built in the Qin dynasty in the 3rd century BC

Hot springs have been used for bathing at least since Paleolithic times.[12] The oldest known spa is a stone pool on China's Lisan mountain built in the Qin Dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built. In the first century AD, 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 14th century.[13] 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.[14] 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.[15] 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.

Geothermal capacity
Global geothermal electric capacity. Upper red line is installed capacity;[16] lower green line is realized production.[7]

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.[17] 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.[18]

Lord Kelvin invented the heat pump in 1852, and Heinrich Zoelly had patented the idea of using it to draw heat from the ground in 1912.[19] But it was not until the late 1940s that the geothermal heat pump was successfully implemented. The earliest one was probably Robert C. Webber's home-made 2.2 kW direct-exchange system, but sources disagree as to the exact timeline of his invention.[19] J. Donald Kroeker designed the first commercial geothermal heat pump to heat the Commonwealth Building (Portland, Oregon) and demonstrated it in 1946.[20][21] Professor Carl Nielsen of Ohio State University built the first residential open loop version in his home in 1948.[22] The technology became popular in Sweden as a result of the 1973 oil crisis, and has been growing slowly in worldwide acceptance since then. The 1979 development of polybutylene pipe greatly augmented the heat pump's economic viability.[20]

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.[23] The original turbine lasted for more than 30 years and produced 11 MW net power.[24]

The binary cycle power plant was first demonstrated in 1967 in the USSR and later introduced to the US in 1981.[23] 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 57 °C (135 °F).[25]

Electricity

Direct Use Data 2015
Country Usage (MWt) 2015

[26]

United States 17,415.91
Philippines 3.30
Indonesia 2.30
Mexico 155.82
Italy 1,014.00
New Zealand 487.45
Iceland 2,040.00
Japan 2,186.17
Iran 81.50
El Salvador 3.36
Kenya 22.40
Costa Rica 1.00
Russia 308.20
Turkey 2,886.30
Papua-New Guinea 0.10
Guatemala 2.31
Portugal 35.20
China 17,870.00
France 2,346.90
Ethiopia 2.20
Germany 2,848.60
Austria 903.40
Australia 16.09
Thailand 128.51

The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of geothermal power in 24 countries is online, which was expected to generate 67,246 GWh of electricity in 2010.[27] This represents a 20% increase in online capacity since 2005. IGA projects growth to 18,500 MW by 2015, due to the projects presently under consideration, often in areas previously assumed to have little exploitable resources.[27]

In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants.[28] The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California.[29] The Philippines is the second highest producer, with 1,904 MW of capacity online. Geothermal power makes up approximately 27% of Philippine electricity generation.[28]

In 2016, Indonesia set in third with 1,647 MW online behind USA at 3,450 MW and the Philippines at 1,870 MW, but Indonesia will become second due to an additional online 130 MW at the end of 2016 and 255 MW in 2017. Indonesia's 28,994 MW are the largest geothermal reserves in the world, and it is predicted to overtake the US in the next decade.[30]

Installed geothermal electric capacity
Country Capacity (MW)
2007[16]
Capacity (MW)
2010[31]
Percentage of national
electricity production
Percentage of global
geothermal production
United States 2687 3086 0.3 29
Philippines 1969.7 1904 27 18
Indonesia 992 1197 3.7 11
Mexico 953 958 3 9
Italy 810.5 843 1.5 8
New Zealand 471.6 628 10 6
Iceland 421.2 575 30 5
Japan 535.2 536 0.1 5
Iran 250 250
El Salvador 204.2 204 25
Kenya 128.8 167 11.2
Costa Rica 162.5 166 14
Nicaragua 87.4 88 10
Russia 79 82
Turkey 38 82
Papua-New Guinea 56 56
Guatemala 53 52
Portugal 23 29
China 27.8 24
France 14.7 16
Ethiopia 7.3 7.3
Germany 8.4 6.6
Austria 1.1 1.4
Australia 0.2 1.1
Thailand 0.3 0.3
TOTAL 9,981.9 10,959.7

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.[32] 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.[33]

The thermal efficiency of geothermal electric plants is low, around 10–23%, because geothermal fluids do not reach the high temperatures of steam from boilers. The laws of thermodynamics limits the efficiency of heat engines in extracting useful energy. Exhaust heat is wasted, unless it can be used directly and locally, for example in greenhouses, timber mills, and district heating. System efficiency does not materially affect operational costs as it would for plants that use fuel, but it does affect return on the capital used to build the plant. In order to produce more energy than the pumps consume, electricity generation requires relatively hot 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.[34] The global average was 73% in 2005.

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 200 °C (392 °F) 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 MWe. Steam is separated from 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 MWe from temperatures reaching 350 °C (662 °F). The Salton Sea field in Southern California offers the potential of generating 2000 MWe.[18]

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.[18][35]

Thermal energy

Lower temperature sources produce the energy equivalent of 100M BBL per year. 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. Heat pumps extract energy from shallow sources at 10–20 °C in 43 countries for use in space heating and cooling. Home heating is the fastest-growing means of exploiting geothermal energy, with global annual growth rate of 30% in 2005[36] and 20% in 2012.[18][35]

Approximately 270 petajoules (PJ) of geothermal heating was used in 2004. More than half went for space heating, and another third for heated pools. The remainder supported industrial and agricultural applications. Global installed capacity was 28 GW, but capacity factors tend to be low (30% on average) since heat is mostly needed in winter. Some 88 PJ for space heating was extracted by an estimated 1.3 million geothermal heat pumps with a total capacity of 15 GW.[7]

Heat for these purposes may also be extracted from co-generation at a geothermal electrical plant.

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 hot, dry ground, earth tubes or downhole heat exchangers can collect the heat. However, even in areas where the ground is colder than room temperature, heat can often be extracted with a geothermal heat pump more cost-effectively and cleanly than by conventional furnaces.[37] These devices draw on much shallower and colder resources than traditional geothermal techniques. They frequently combine functions, including air conditioning, seasonal thermal energy storage, solar energy collection, and electric heating. Heat pumps can be used for space heating essentially anywhere.

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.[38] Once known as the most polluted city in the world, it is now one of the cleanest.[39]

Enhanced geothermal

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.[18]

Small-scale EGS have been installed in the Rhine Graben at Soultz-sous-Forêts in France and at Landau and Insheim in Germany.[18]

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.[40]

Sonoma Plant at The Geysers 4778
A power plant at The Geysers

In total, electrical plant construction and well drilling cost about €2–5 million per MW of electrical capacity, while the break–even price is 0.04–0.10 € per kW·h.[16] Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4 million per MW and break–even above $0.054 per kW·h in 2007.[41] Direct heating applications can use much shallower wells with lower temperatures, so smaller systems with lower costs and risks are feasible. Residential geothermal heat pumps with a capacity of 10 kilowatt (kW) are routinely installed for around $1–3,000 per kilowatt. District heating systems may benefit from economies of scale if demand is geographically dense, as in cities and greenhouses, but otherwise piping installation dominates capital costs. The capital cost of one such district heating system in Bavaria was estimated at somewhat over 1 million € per MW.[42] Direct systems of any size are much simpler than electric generators and have lower maintenance costs per kW·h, but they must consume electricity to run pumps and compressors. Some governments subsidize geothermal projects.

Geothermal power is highly scalable: from a rural village to an entire city.[43]

The most developed geothermal field in the United States is The Geysers in Northern California.[44]

Geothermal projects have several stages of development. Each phase has associated risks. At the early stages of reconnaissance and geophysical surveys, many projects are cancelled, making that phase unsuitable for traditional lending. Projects moving forward from the identification, exploration and exploratory drilling often trade equity for financing.[45]

Resources

EGS diagram
Enhanced geothermal system 1:Reservoir 2:Pump house 3:Heat exchanger 4:Turbine hall 5:Production well 6:Injection well 7:Hot water to district heating 8:Porous sediments 9:Observation well 10:Crystalline bedrock

The Earth's internal thermal energy flows to the surface by conduction at a rate of 44.2 terawatts (TW),[46] and is replenished by radioactive decay of minerals at a rate of 30 TW.[47] These power rates are more than double humanity's current energy consumption from all primary sources, but most of this energy flow is not recoverable. In addition to the internal heat flows, the top layer of the surface to a depth of 10 meters (33 ft) is heated by solar energy during the summer, and releases that energy and cools during the winter.

Outside of the seasonal variations, the geothermal gradient of temperatures through the crust is 25–30 °C (77–86 °F) per kilometer of depth in most of the world. The conductive heat flux averages 0.1 MW/km2. These values are much higher near tectonic plate boundaries where the crust is thinner. They may be further augmented by fluid circulation, either through magma conduits, hot springs, hydrothermal circulation or a combination of these.

A geothermal heat pump can extract enough heat from shallow ground anywhere in the world to provide home heating, but industrial applications need the higher temperatures of deep resources.[13] The thermal efficiency and profitability of electricity generation is particularly sensitive to temperature. The most demanding applications receive the greatest benefit from a high natural heat flux, ideally from using a hot spring. The next best option is to drill a well into a hot aquifer. If no adequate aquifer is available, an artificial one may be built by injecting water to hydraulically fracture the bedrock. This last 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.[32]

Estimates of the potential for electricity generation from geothermal energy vary sixfold, from .035to2TW depending on the scale of investments.[7] Upper estimates of geothermal resources assume enhanced geothermal wells as deep as 10 kilometres (6 mi), whereas existing geothermal wells are rarely more than 3 kilometres (2 mi) deep.[7] Wells of this depth are now common in the petroleum industry. The deepest research well in the world, the Kola superdeep borehole, is 12 kilometres (7 mi) deep.[48]

Myanmar Engineering Society has identified at least 39 locations (in Myanmar) capable of geothermal power production and some of these hydrothermal reservoirs lie quite close to Yangon which is a significant underutilized resource.[49]

Production

According to the Geothermal Energy Association (GEA) installed geothermal capacity in the United States grew by 5%, or 147.05 MW, since the last annual survey in March 2012. This increase came from seven geothermal projects that began production in 2012. GEA also revised its 2011 estimate of installed capacity upward by 128 MW, bringing current installed U.S. geothermal capacity to 3,386 MW.[50]

Renewability and sustainability

Geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth's heat content. The Earth has an internal heat content of 1031 joules (3·1015 TW·hr), approximately 100 billion times the 2010 worldwide annual energy consumption.[7] About 20% of this is residual heat from planetary accretion, and the remainder is attributed to higher radioactive decay rates that existed in the past.[3] Natural heat flows are not in equilibrium, and the planet is slowly cooling down on geologic timescales. Human extraction taps a minute fraction of the natural outflow, often without accelerating it.

Geothermal power is also considered to be sustainable thanks to its power to sustain the Earth's intricate ecosystems. By using geothermal sources of energy present generations of humans will not endanger the capability of future generations to use their own resources to the same amount that those energy sources are presently used.[51] Further, due to its low emissions geothermal energy is considered to have excellent potential for mitigation of global warming.

Even though geothermal power is globally sustainable, extraction must still be monitored to avoid local depletion.[47] Over the course of decades, individual wells draw down local temperatures and water levels until a new equilibrium is reached with natural flows. The three oldest sites, at Larderello, Wairakei, and the Geysers have experienced reduced output because of local depletion. Heat and water, in uncertain proportions, were extracted faster than they were replenished. 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,[52] and at The Geysers field in California since 1960.[53]

Geothermal.Electricity.NZ.Poihipi
Electricity Generation at Poihipi, New Zealand
Geothermal.Electricity.NZ.Ohaaki
Electricity Generation at Ohaaki, New Zealand
Geothermal.Electricity.NZ.Wairakei
Electricity Generation at Wairakei, New Zealand

Falling electricity production may be boosted through drilling additional supply boreholes, as at Poihipi and Ohaaki. The Wairakei power station has been running much longer, with its first unit commissioned in November 1958, and it attained its peak generation of 173MW in 1965, but already the supply of high-pressure steam was faltering, in 1982 being derated to intermediate pressure and the station managing 157MW. Around the start of the 21st century it was managing about 150MW, then in 2005 two 8MW isopentane systems were added, boosting the station's output by about 14MW. Detailed data are unavailable, being lost due to re-organisations. One such re-organisation in 1996 causes the absence of early data for Poihipi (started 1996), and the gap in 1996/7 for Wairakei and Ohaaki; half-hourly data for Ohaaki's first few months of operation are also missing, as well as for most of Wairakei's history.

Environmental effects

Puhagan geothermal plant
Geothermal power station in the Philippines
Krafla Geothermal Station
Krafla Geothermal Station in northeast Iceland

Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide (CO
2
), hydrogen sulfide (H
2
S
), methane (CH
4
) and ammonia (NH
3
). These pollutants contribute to global warming, acid rain, and noxious smells if released. Existing geothermal electric plants emit an average of 122 kilograms (269 lb) of CO
2
per megawatt-hour (MW·h) of electricity, a small fraction of the emission intensity of conventional fossil fuel plants.[54] Plants that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust.

In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic elements such as mercury, arsenic, boron, and antimony.[55] These chemicals precipitate as the water cools, and can cause environmental damage if released. The modern practice of injecting cooled geothermal fluids back into the Earth to stimulate production has the side benefit of reducing this environmental risk.

Direct geothermal heating systems contain pumps and compressors, which may consume energy from a polluting source. This parasitic load is normally a fraction of the heat output, so it is always less polluting than electric heating. However, if the electricity is produced by burning fossil fuels, then the net emissions of geothermal heating may be comparable to directly burning the fuel for heat. For example, a geothermal heat pump powered by electricity from a combined cycle natural gas plant would produce about as much pollution as a natural gas condensing furnace of the same size.[37] Therefore, the environmental value of direct geothermal heating applications is highly dependent on the emissions intensity of the neighboring electric grid.

Plant construction can adversely affect land stability. Subsidence has occurred in the Wairakei field in New Zealand.[13] In Staufen im Breisgau, Germany, tectonic uplift occurred instead, due to a previously isolated anhydrite layer coming in contact with water and turning into gypsum, doubling its volume.[56][57][58] Enhanced geothermal systems can trigger earthquakes 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.[59]

Geothermal has minimal land and freshwater requirements. Geothermal plants use 3.5 square kilometres (1.4 sq mi) per gigawatt of electrical production (not capacity) versus 32 square kilometres (12 sq mi) and 12 square kilometres (4.6 sq mi) for coal facilities and wind farms respectively.[13] They use 20 litres (5.3 US gal) of freshwater per MW·h versus over 1,000 litres (260 US gal) per MW·h for nuclear, coal, or oil.[13]

Legal frameworks

Some of the legal issues raised by geothermal energy resources include questions of ownership and allocation of the resource, the grant of exploration permits, exploitation rights, royalties, and the extent to which geothermal energy issues have been recognized in existing planning and environmental laws. Other questions concern overlap between geothermal and mineral or petroleum tenements. Broader issues concern the extent to which the legal framework for encouragement of renewable energy assists in encouraging geothermal industry innovation and development.

See also

References

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Bibliography

Energy in Mexico

Energy in Mexico describes energy and electricity production, consumption and import in Mexico.

In 2008, Mexico produced 234 TWh of electricity, of which, 86 TWh was from thermal plants, 39 TWh from hydropower, 18 TWh from coal, 9.8 TWh from nuclear power, 7 TWh from geothermal power and 0.255 TWh from wind power. Mexico is among the world's top oil producers and exporters.

Geothermal energy in the United States

Geothermal energy in the United States was first used for electric power production in 1960. The Geysers in California was developed into what is now the largest geothermal steam electrical plant in the world, at 750 megawatts. Other geothermal steam fields are known in the western United States and Alaska. Geothermally-generated electric power can be dispatchable to follow the demands of changing loads. Environmental impact of this energy source includes hydrogen sulfide emissions, corrosive or saline chemicals discharged in waste water, possible seismic effects from water injection into rock formations, wast heat and noise.

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 6 metres (20 ft) the undisturbed ground temperature is consistently at the Mean Annual Air Temperature and it may be extracted with a heat pump.

Geothermal power

Geothermal power is power generated by 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, while geothermal heating is in use in 70 countries.As of 2015, worldwide geothermal power capacity amounts to 12.8 gigawatts (GW), of which 28 percent or 3,548 megawatts (MW) 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.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.

Geothermal power in Australia

Geothermal power in Australia is little used but growing. There are known and potential locations near the centre of the country that have been shown to contain hot granites at depth which hold good potential for development of geothermal energy. Exploratory geothermal wells have been drilled to test for the presence of high temperature geothermal reservoir rocks and such hot granites were detected. As a result, projects will eventuate in the coming years and more exploration is expected to find new locations.

Geothermal power in Chile

Chile represents one of the largest undeveloped geothermal areas of the world. Despite Chile's good economic performance in the late 1980s and 1990s, geothermal energy did not develop, and Chile has been surpassed by other Latin American countries such as El Salvador and Costa Rica in terms of geothermal development and technology. Currently Chile has only one geothermal power plant.

The first geothermal explorations in Chile were carried out by Italians living in the city of Antofagasta in 1908, but it was not until 1968 that systematic exploration started in the north of the country. These later explorations occurred amidst a global wave of research and development of the geothermal power. The exploration were carried out after an agreement between the Government of Chile and United Nations Development Programme were state agency CORFO (Production Development Corporation) created a comité to direct and carry out exploration in the northern regions of Chile. These explorations did however end in 1976 when the military government headed by Pinochet withdrew Chile from the cooperation program.

High prices of oil, unreliability in gas imports from Argentina and a continuously growing electricity demand have led the Chilean governments to further promote new energy sources in the late 1990s and 2000s. New interest in geothermal energy resulted in 2000 in the promulgation of the Law of Geothermal Concessions that regulates exploitation and exploration of geothermal resources.

Geothermal power in China

Geothermal exploration began in China in the 1970s. It was initially handled by national bodies with public investments, and productive wells were transferred free of charge to the final user. Since the mid-1980s, under the framework of privatization and liberalization of the economy, national investment in exploration has been reduced. No new plants have been commissioned in the period 2000–2005 (Zheng et al., 2005; Battocletti et al., 2000). The only electricity-producing fields are located in Tibet. According to the "2005 Chinese Geothermal Environment Bulletin" by China's Ministry of Land and Resources, the direct utilization of geothermal energy in China will reach 13.76 cubic meters per second, and the geothermal energy will reach 10,779 megawatts, ranking first in the world.

Geothermal power in Iceland

Due to the geological location of Iceland (over a rift in continental plates), the high concentration of volcanoes in the area is often an advantage in the generation of geothermal energy, the heating and making of electricity. During winter, pavements near these areas (such as Reykjavik and Akureyri) are heated up.

Five major geothermal power plants exist in Iceland, which produce approximately 26.2% (2010) of the nation's electricity. In addition, geothermal heating meets the heating and hot water requirements of approximately 87% of all buildings in Iceland. Apart from geothermal energy, 73.8% of the nation’s electricity is generated by hydro power, and 0.1% from fossil fuels. Hydrogen sulfide (H2S) from geothermal energy has impacted the health of Icelanders.Consumption of primary geothermal energy in 2004 was 79.7 petajoules (PJ), approximately 53.4% of the total national consumption of primary energy, 149.1 PJ. The corresponding share for hydro power was 17.2%, petroleum was 26.3%, and coal was 3%. Plans are underway to turn Iceland into a 100% fossil-fuel-free nation in the near future. For example, Iceland's abundant geothermal energy has enabled renewable energy initiatives, such as Carbon Recycling International's carbon dioxide to methanol fuel process.Geothermal energy also provides tourist attractions such as the Blue Lagoon. The geothermal water originates 2,000 metres below the surface, where freshwater and seawater combine at extreme temperatures. It is then harnessed via drilling holes at a nearby geothermal power plant, Svartsengi, to create electricity and hot water for nearby communities. This Blue Lagoon is entirely powered by geothermal energy.The following are the six largest power stations in Iceland:

Hellisheiði Power Station (303 MW)

Nesjavellir Geothermal Power Station (120 MW)

Reykjanes Power Station (100 MW)

Svartsengi Power Station (76.5 MW)

Krafla Power Station (60 MW)

Þeistareykir Power Station (45 MW)

Geothermal power in Kenya

Geothermal power is very cost-effective in the Great Rift Valley of Kenya, East Africa. As of 2019, Kenya has 690 MW of installed geothermal capacity. Kenya was the first African country to build geothermal energy sources. The Kenya Electricity Generating Company, which is 74% state-owned, has built three plants to exploit the Olkaria geothermal resource, Olkaria I (195 MW), Olkaria II (105 MW) and Olkaria IV (150 MW, 75 MW Wellhead generation plants, with a third private plant Olkaria III (139 MW). Additionally, a pilot wellhead plant of 2.5 MW has been commissioned at Eburru and two small scale plants have been built by the Oserian Development Company to power their rose farm facilities with a total of 4 MW.

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 17% of the country's electricity with installed capacity of over 900MW. New Zealand, like only a small number of other countries worldwide, has numerous geothermal sites that could be developed for exploitation, and also boasts some of the earliest large-scale use of geothermal energy in the world.

Geothermal energy has been described as New Zealand's most reliable renewable energy source, above wind, solar and even hydroelectricity, due to its lack of dependence on the weather. It has also been described as the currently (2000s and 2010s) most attractive new source of energy for New Zealand, as petrochemical fuel prices rise and easy hydro power sites have been tapped - it has been estimated that another 1000MW of geothermal resource can be used for generating electricity.

Geothermal power in Romania

Geothermal energy in Romania is mainly located, in the western part of the country, in the Banat region and the western part of the Apuseni Mountains with the most important source located in the Bihor County especially around the city of Oradea, that has been using geothermal energy for more than a hundred years. Theoretically Romania has the third highest potential geothermal capacity in Europe after Greece and Italy.

The direct-use heating has been mostly district heating serving 5,500 residences in Oradea and the city of Beiuş is the only city in Romania entirely heated by geothermal energy. Romania has a total of 200 drilled wells at depths between 800 m (2,600 ft) and 3,400 m (11,200 ft) and a capacity of 480 MWt with a utilisation of 7,975 TJ/year or 2,215 GWh/year.

Geothermal power in Russia

Geothermal energy is the second most used form of renewable energy in Russia but represents less than 1% of the total energy production. The first geothermal power plant in Russia,which was the first Binary cycle power station in world, was built at Pauzhetka, Kamchatka, in 1966, with a capacity of 5 MW.the first binary cycle power station The total geothermal installed capacity is 81.9 MW, with 50 MW coming from a plant at Verkhne-Mutnovsky.Two other plants were built on the Kamchatka Peninsula in 1999 and 2002. Two smaller additional plants were installed on the islands of Kunashir and Iturup in 2007. Russia is currently developing a 100 MW plant at Mutnovsky and a 50 MW plant in Kaliningrad. Most geothermal resources are currently used for heating settlements in the North Caucasus and Kamchatka.

Half of the geothermal production is used to heat homes and industrial buildings, one third is used to heat greenhouses and 13% is used for industrial processes.Five major geothermal power plants exist in Russia.Russia currently deveploing a new 100 MW geothermal power plant at Mutnovsky and a 50 MW plant in Kaliningrad.Potential resources include the Northern Caucasus, Western Siberia, Lake Baikal, and in Kamchatka and the Kuril Islands.

Geothermal power in the United Kingdom

The potential for exploiting geothermal energy in the United Kingdom on a commercial basis was initially examined by the Department of Energy in the wake of the 1973 oil crisis. Several regions of the country were identified, but interest in developing them was lost as petroleum prices fell. Although the UK is not actively volcanic, a large heat resource is potentially available via shallow geothermal ground source heat pumps, shallow aquifers and deep saline aquifers in the mesozoic basins of the UK. Geothermal energy is plentiful beneath the UK, although it is not readily accessible currently except in specific locations.

Renewable energy in Albania

Renewable energy in Albania includes biomass, geothermal, hydropower, solar, and wind energy. Albania relies mostly on hydroelectric resources, therefore, it has difficulties when water levels are low. The climate in Albania is Mediterranean, so it possesses considerable potential for solar energy production. Mountain elevations provide good areas for wind projects. There is also potentially usable geothermal energy because Albania has natural wells.

Renewable energy in Bangladesh

Renewable energy in Bangladesh refers to the use of renewable energy to generate electricity in Bangladesh. The current renewable energy comes from biogas that is originated from biomass, hydro power, solar and wind.

Renewable energy in Colombia

Colombia has 28.1 Megawatt installed capacity of renewable energy (excluding large hydropower), consisting mainly of wind power. The country has significant wind and solar resources that remain largely unexploited. According to a study by the World Bank’s Energy Sector Management Assistance Program (ESMAP), exploitation of the country’s significant wind potential alone could cover more than the country’s current total energy needs.

Renewable energy in Ethiopia

Ethiopia generates most of its electricity from renewable energy, mainly hydropower.

Renewable energy in Hungary

Hungary is a member of the European Union and thus takes part in the EU strategy to increase its share of renewable energy. The EU has adopted the 2009 Renewable Energy Directive, which included a 20% renewable energy target by 2020 for the EU. By 2030 wind should produce in average 26-35% of the EU's electricity and save Europe €56 billion a year in avoided fuel costs.

The national authors of Hungary forecast is 14.7% renewables in gross energy consumption by 2020, exceeding their 13% binding target by 1.7 percentage points. Hungary is the EU country with the smallest forecast penetration of renewables of the electricity demand in 2020, namely only 11% (including biomass 6% and wind power 3%).

Renewable energy in Lithuania

In 2016 Renewable energy in Lithuania constituted 27.9% of the country's overall electricity generation. Previously, the Lithuanian government aimed to generate 23% of total power from renewable resources by 2020, a goal was achieved in 2014 (23.9).

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