An enhanced geothermal system (EGS) generates geothermal electricity without natural convective hydrothermal resources. Traditionally, geothermal power systems operated only where naturally occurring heat, water, and rock permeability are sufficient to allow energy extraction. [1] However, most geothermal energy within reach of conventional techniques is in dry and impermeable rock. [2] EGS technologies expand the availability of geothermal resources through stimulation methods, such as 'hydraulic stimulation'.
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In many rock formations natural cracks and pores do not allow water to flow at economic rates. Permeability can be enhanced by hydro-shearing, pumping high-pressure water down an injection well into naturally-fractured rock. The injection increases the fluid pressure in the rock, triggering shear events that expand pre-existing cracks and enhance the site's permeability. As long as the injection pressure is maintained, high permeability is not required, nor are hydraulic fracturing proppants required to maintain the fractures in an open state. [3]
Hydro-shearing is different from hydraulic tensile fracturing, used in the oil and gas industry, which can create new fractures in addition to expanding existing fractures. [4]
Water passes through the fractures, absorbing heat until forced to the surface as hot water. The water's heat is converted into electricity using either a steam turbine or a binary power plant system, which cools the water. [5] The water is cycled back into the ground to repeat the process.
EGS plants are baseload resources that produce power at a constant rate. Unlike hydrothermal, EGS is apparently feasible anywhere in the world, depending on the resource depth. Good locations are typically over deep granite covered by a 3–5 kilometres (1.9–3.1 mi) layer of insulating sediments that slow heat loss. [6]
Advanced drilling techniques penetrate hard crystalline rock at depths of up to or exceeding 15 km, which give access to higher-temperature rock (400 °C and above), as temperature increases with depth. [7]
EGS plants are expected to have an economic lifetime of 20–30 years. [8]
EGS systems are under development in Australia, France, Germany, Japan, Switzerland, and the United States. The world's largest EGS project is a 25-megawatt demonstration plant in Cooper Basin, Australia. Cooper Basin has the potential to generate 5,000–10,000 MW.
EGS technologies use a variety of methods to create additional flow paths. EGS projects have combined hydraulic, chemical, thermal, and explosive stimulation methods. Some EGS projects operate at the edges of hydrothermal sites where drilled wells intersect hot, yet impermeable, reservoir rocks. Stimulation methods enhance that permeability. The table below shows EGS projects around the world. [9] [10]
Name | Country | State/region | Year Start | Stimulation method | References |
---|---|---|---|---|---|
Mosfellssveit | Iceland | 1970 | Thermal and hydraulic | [11] | |
Fenton Hill | USA | New Mexico | 1973 | Hydraulic and chemical | [12] |
Bad Urach | Germany | 1977 | Hydraulic | [13] | |
Falkenberg | Germany | 1977 | Hydraulic | [14] | |
Rosemanowes | UK | 1977 | Hydraulic and explosive | [15] | |
Le Mayet | France | 1978 | Hydraulic | , [16] [17] | |
East Mesa | USA | California | 1980 | Hydraulic | [18] |
Krafla | Iceland | 1980 | Thermal | [19] | |
Baca | USA | New Mexico | 1981 | Hydraulic | [18] |
Geysers Unocal | USA | California | 1981 | Explosive | [18] |
Beowawe | USA | Nevada | 1983 | Hydraulic | [18] |
Bruchal | Germany | 1983 | Hydraulic | [20] | |
Fjällbacka | Sweden | 1984 | Hydraulic and chemical | [21] | |
Neustadt-Glewe | Germany | 1984 | [20] | ||
Hijiori | Japan | 1985 | Hydraulic | [22] | |
Soultz | France | 1986 | Hydraulic and chemical | [23] | |
Altheim | Austria | 1989 | Chemical | [24] | |
Hachimantai | Japan | 1989 | Hydraulic | [25] | |
Ogachi | Japan | 1989 | Hydraulic | [26] | |
Sumikawa | Japan | 1989 | Thermal | [27] | |
Tyrnyauz | Russia | ` | 1991 | Hydraulic | , [28] [29] |
Bacman | Philippines | 1993 | Chemical | [30] | |
Seltjarnarnes | Iceland | 1994 | Hydraulic | [31] | |
Mindanao | Philippines | 1995 | Chemical | [32] | |
Bouillante | France | 1996 | Thermal | [33] | |
Leyte | Philippines | 1996 | Chemical | [34] | |
Hunter Valley | Australia | 1999 | [8] | ||
Groß Schönebeck | Germany | 2000 | Hydraulic and chemical | [35] | |
Tiwi | Philippines | 2000 | Chemical | [36] | |
Berlin | El Salvador | 2001 | Chemical | [37] | |
Cooper Basin: Habanero | Australia | 2002 | Hydraulic | [38] | |
Cooper Basin: Jolokia 1 | Australia | 2002 | Hydraulic | [38] | |
Coso | USA | California | 1993, 2005 | Hydraulic and chemical | [39] |
Hellisheidi | Iceland | 1993 | Thermal | [40] | |
Genesys: Horstberg | Germany | 2003 | Hydraulic | [41] | |
Landau | Germany | 2003 | Hydraulic | [42] | |
Unterhaching | Germany | 2004 | Chemical | [43] | |
Salak | Indonesia | 2004 | Chemical, thermal, hydraulic and cyclic pressure loading | [44] | |
Olympic Dam | Australia | 2005 | Hydraulic | [45] | |
Paralana | Australia | 2005 | Hydraulic and chemical | [46] | |
Los Azufres | Mexico | 2005 | Chemical | [47] | |
Basel | Switzerland | 2006 | Hydraulic | [48] | |
Larderello | Italy | 1983, 2006 | Hydraulic and chemical | [49] | |
Insheim | Germany | 2007 | Hydraulic | [50] | |
Desert Peak | USA | Nevada | 2008 | Hydraulic and chemical | [51] |
Brady Hot Springs | USA | Nevada | 2008 | Hydraulic | [52] |
Southeast Geysers | USA | California | 2008 | Hydraulic | [53] |
Genesys: Hannover | Germany | 2009 | Hydraulic | [54] | |
St. Gallen | Switzerland | 2009 | Hydraulic and chemical | [55] | |
New York Canyon | USA | Nevada | 2009 | Hydraulic | [56] |
Northwest Geysers | USA | California | 2009 | Thermal | [57] |
Newberry | USA | Oregon | 2010 | Hydraulic | [58] |
Mauerstetten | Germany | 2011 | Hydraulic and chemical | [59] | |
Soda Lake | USA | Nevada | 2011 | Explosive | [60] |
Raft River | USA | Idaho | 1979, 2012 | Hydraulic and thermal | [61] |
Blue Mountain | USA | Nevada | 2012 | Hydraulic | [62] |
Rittershoffen | France | 2013 | Thermal, hydraulic and chemical | [63] | |
Klaipėda | Lithuania | 2015 | Jetting | [64] | |
Otaniemi | Finland | 2016 | Hydraulic | [65] | |
South Hungary EGS Demo | Hungary | 2016 | Hydraulic | [66] | |
Pohang | South Korea | 2016 | Hydraulic | [67] | |
FORGE Utah | USA | Utah | 2016 | Hydraulic | [68] |
Reykjanes | Iceland | 2006, 2017 | Thermal | [69] | |
Roter Kamm (Schneeberg) | Germany | 2018 | Hydraulic | [70] | |
United Downs Deep Geothermal Power (Redruth) | UK | 2018 | Hydraulic | [71] | |
Eden (St Austell) | UK | 2018 | Hydraulic | [72] | |
Qiabuqia | China | 2018 | Thermal and hydraulic | [73] | |
Vendenheim | France | 2019 | [74] |
The Australian government has provided research funding for the development of Hot Dry Rock technology. Projects include Hunter Valley (1999), Cooper Basin: Habanero (2002), Cooper Basin: Jolokia 1 (2002), and Olympic Dam (2005). [75]
This section needs to be updated.(June 2022) |
The EU's EGS R&D project at Soultz-sous-Forêts, France, connects a 1.5 MW demonstration plant to the grid. The Soultz project explored the connection of multiple stimulated zones and the performance of triplet well configurations (1 injector/2 producers). Soultz is in the Alsace.
Induced seismicity in Basel led to the cancellation of the EGS project there.[ citation needed ]
The Portuguese government awarded, in December 2008, an exclusive license to Geovita Ltd to prospect and explore geothermal energy in one of the best areas in continental Portugal. Geovita is studying an area of about 500 square kilometers together with the Earth Sciences department of the University of Coimbra's Science and Technology faculty.[ citation needed ]
The Pohang EGS project started in December 2010, with the goal of producing 1 MW. [76]
The 2017 Pohang earthquake may have been linked to the activity of the Pohang EGS project. All research activities were stopped in 2018.
The first EGS effort — then termed Hot Dry Rock — took place at Fenton Hill, New Mexico with a project run by the federal Los Alamos Laboratory. [79] It was the first attempt to make a deep, full-scale EGS reservoir.
The EGS reservoir at Fenton Hill was completed in 1977 at a depth of about 2.6 km, exploiting rock temperatures of 185 °C. In 1979 the reservoir was enlarged with additional hydraulic stimulation and was operated for about 1 year. The results demonstrated that heat could be extracted at reasonable rates from a hydraulically stimulated region of low-permeability hot crystalline rock. In 1986, a second reservoir was prepared for initial hydraulic circulation and heat extraction testing. In a 30-day flow test with a constant reinjection temperature of 20 °C, the production temperature steadily increased to about 190 °C, corresponding to a thermal power level of about 10 MW. Budget cuts ended the study.
In 2009, The US Department of Energy (USDOE) issued two Funding Opportunity Announcements (FOAs) related to enhanced geothermal systems. Together, the two FOAs offered up to $84 million over six years. [80]
The DOE opened another FOA in 2009 using stimulus funding from the American Reinvestment and Recovery Act for $350 million, including $80 million aimed specifically at EGS projects, [81]
Developing EGS in conjunction with a district heating system is a part in Cornell University's Climate Action Plan for their Ithaca campus. [84] The project began in 2018 to determine feasibility, gain funding and monitor baseline seismicity. [85] The project received $7.2 million in USDOE funding. [86] A test well was to be drilled in spring of 2021, at a depth of 2.5 –5 km targeting rock with a temperature > 85 °C. The site is planned to supply 20% of the campus' annual heating load. Promising geological locations for reservoir were proposed in the Trenton-Black River formation (2.2 km) or in basement crystalline rock (3.5 km). [87] The 2 mile deep borehole was completed in 2022. [88]
In September 2022, the Geothermal Technologies Office within the Department of Energy's Office of Energy Efficiency and Renewable Energy announced an "Enhanced Geothermal Shot" as part of their Energy Earthshots campaign. [89] The goal of the Earthshot is to reduce the cost of EGS by 90%, to $45/megawatt hour by 2035. [90]
The Infrastructure Investment and Jobs Act authorized $84 million to support EGS development through four demonstration projects. [91] The Inflation Reduction Act extended the production tax credit (PTC) for renewable energy sources (including geothermal) until 2024 and included geothermal energy in the new Clean Electricity PTC to begin in 2024. [92]
Induced seismicity is earth tremors caused by human activity. Seismicity is common in EGS, because of the high pressures involved. [93] [94] Seismicity events at the Geysers geothermal field in California are correlated with injection activity. [95]
Induced seismicity in Basel led the city to suspend its project and later cancel the project. [96]
According to the Australian government, risks associated with "hydrofracturing induced seismicity are low compared to that of natural earthquakes, and can be reduced by careful management and monitoring" and "should not be regarded as an impediment to further development". [97] Induced seismicity varies from site to site and should be assessed before large scale fluid injection.
A 2006 report by MIT, [8] funded by the U.S. Department of Energy, conducted the most comprehensive analysis to date on EGS. The report offered several significant conclusions:
Hot dry rock (HDR) is an abundant source of geothermal energy, but it is typically difficult to access. Hot, dry crystalline basement rocks are found almost everywhere sufficiently far beneath the surface. [98] One extraction method originated at Los Alamos National Laboratory in 1970. Laboratory researchers were awarded a US patent covering it. [99] HDR consists of a pressurized HDR reservoir, boreholes, and injection pumps and associated plumbing. An associated power plant turns the hot water into electricity.
This technology has been tested with multiple deep wells drilled around the world, including the US, Japan, Australia, France, and the UK. [100]
HDR is the focus of multiple research studies. Thermal energy has been recovered in reasonably sustainable tests over periods of years and in some cases electrical power generation has been achieved. Ongoing efforts are underway to further develop and test EGS technologies in hot dry rock systems. [101] EGS in hot dry rock has not been commercialized, but one estimate suggests a price of $20–35 per MWh given sufficient experience. [102]
Whereas hydrothermal energy production can exploit already present hot fluids, HDR recovers heat from dry rock via the closed-loop circulation of pressurized fluid. This fluid, injected from the surface under high pressure, expands pre-existing joints in the rock, creating a reservoir that can be as much as a cubic kilometer in size.
The idea of deep hot dry rocks heat mining was described by Konstantin Tsiolkovsky (1898), Charles Parsons (1904), and Vladimir Obruchev (1920). [103]
In 1963 in Paris, a geothermal heating system that used the heat of natural fractured rocks was built. [103]
The Fenton Hill project was the first system for extracting HDR geothermal energy from an artificial formed reservoir; it was created in 1977. [103]
As the reservoir is formed by the pressure-dilation of the joints, the elastic response of the surrounding rock mass results in a region of tightly compressed, sealed rock at the periphery—making the HDR reservoir totally confined and contained. Such a reservoir is therefore fully engineered, in that the physical characteristics (size, depth at which it is created) as well as the operating parameters (injection and production pressures, production temperature, etc.) can be pre-planned and closely controlled. On the other hand, the tight compression and confined nature of the reservoir severely limits that amount and the rate at which energy can be extracted.
As described by Brown, [104] an HDR geothermal energy system is developed, first, by using conventional drilling to access a region of deep, hot basement rock. Once it has been determined the selected region contains no open faults or joints (by far the most common situation), an isolated section of the first borehole is pressurized at a level high enough to open several sets of previously sealed joints in the rock mass. By continuous pumping (hydraulic stimulation), a very large region of stimulated rock is created (the HDR reservoir) which consists of an interconnected array of joint flow paths within the rock mass. The opening of these flow paths causes movement along the pressure-activated joints, generating seismic signals (microearthquakes). Analysis of these signals yields information about the location and dimensions of the reservoir being developed.
Typically, an HDR reservoir forms in the shape of an ellipsoid, with its longest axis orthogonal to the least principal Earth stress. This pressure-stimulated region is then accessed by two production wells, drilled to intersect the HDR reservoir near the elongated ends of the stimulated region. In most cases, the initial borehole becomes the injection well for the three-well, pressurized water-circulating system.
In operation, fluid is injected at pressures high enough to hold open the interconnected network of joints against the Earth stresses, and to effectively circulate fluid through the HDR reservoir at a high rate. During routine energy production, the injection pressure is maintained at just below the level that would cause further pressure-stimulation of the surrounding rock mass, in order to maximize energy production while limiting further reservoir growth. However, the limited reservoir size limits reservoir energy. Meanwhile, high pressure operation adds significant cost to piping and pumping systems.
The volume of the newly created array of opened joints within the HDR reservoir is much less than 1% of the volume of the pressure-stimulated rock mass. As these joints continue to pressure and cooling -dilate, the overall flow impedance across the reservoir is reduced, leading to a high thermal productivity. If the cooling leads to cooling fractures in a way that exposes more rock then it is possible that these reservoirs may improve over time. To date reservoir energy growth is only reported to come from new expensive high pressure well stimulation efforts.
The feasibility of mining heat from the deep Earth was proven in two separate HDR reservoir flow demonstrations—each involving about one year of circulation—conducted by the Los Alamos National Laboratory between 1978 and 1995. These groundbreaking tests took place at the Laboratory's Fenton Hill HDR test site in the Jemez Mountains of north-central New Mexico, at depths of over 8,000 ft (2,400 m) and rock temperatures in excess of 180 °C. [105] The results of these tests demonstrated conclusively the engineering viability of the revolutionary new HDR geothermal energy concept. The two separate reservoirs created at Fenton Hill are still the only truly confined HDR geothermal energy reservoirs flow-tested anywhere in the world.
The first HDR reservoir tested at Fenton Hill, the Phase I reservoir, was created in June 1977 and then flow-tested for 75 days, from January to April 1978, at a thermal power level of 4 MW. [106] The final water loss rate, at a surface injection pressure of 900 psi (6.2 MPa), was 2 US gallons per minute (7.6 L/min) (2% of the injection rate). This initial reservoir was shown to essentially consist of a single pressure-dilated, near-vertical joint, with a vanishingly small flow impedance of 0.5 psi/US gal/min (0.91 kPa/L/min).
The initial Phase I reservoir was enlarged in 1979 and further flow-tested for almost a year in 1980. [107] Of greatest importance, this flow test confirmed that the enlarged reservoir was also confined, and exhibited a low water loss rate of 6 gpm. This reservoir consisted of the single near-vertical joint of the initial reservoir (which, as noted above, had been flow-tested for 75 days in early 1978) augmented by a set of newly pressure-stimulated near-vertical joints that were somewhat oblique to the strike of the original joint.[ citation needed ]
A deeper and hotter HDR reservoir (Phase II) was created during a massive hydraulic fracturing (MHF) operation in late 1983. [107] It was first flow-tested in the spring of 1985, by an initial closed-loop flow test (ICFT) that lasted a little over a month. [108] Information garnered from the ICFT provided the basis for a subsequent long-term flow test (LTFT), carried out from 1992 to 1995.
The LTFT comprised several individual steady-state flow runs, interspersed with numerous additional experiments. [109] In 1992–1993, two steady-state circulation periods were implemented, the first for 112 days and the second for 55 days. During both tests, water was routinely produced at a temperature of over 180 °C and a rate of 90–100 US gal/min (20–23 m3/h), resulting in continuous thermal energy production of approximately 4 MW. Over this time span, the reservoir pressure was maintained (even during shut-in periods) at a level of about 15 MPa.
Beginning in mid-1993, the reservoir was shut in for a period of nearly two years and the applied pressure was allowed to drop to essentially zero. In the spring of 1995, the system was re-pressurized and a third continuous circulation run of 66 days was conducted. [110] Remarkably, the production parameters observed in the two earlier tests were rapidly re-established, and steady-state energy production resumed at the same level as before. Observations during both the shut-in and operational phases of all these flow-testing periods provided clear evidence that the rock at the boundary of this man-made reservoir had been compressed by the pressurization and resultant expansion of the reservoir region.
As a result of the LTFT, water loss was eliminated as a major concern in HDR operations. [111] Over the period of the LTFT, water consumption fell to just 7% of the quantity of water injected; and data indicated it would have continued to decline under steady-state circulation conditions. Dissolved solids and gases in the produced fluid rapidly reached equilibrium values at low concentrations (about one-tenth the salinity of sea water), and the fluid remained geochemically benign throughout the test period. [112] Routine operation of the automated surface plant showed that HDR energy systems could be run using the same economical staffing schedules that a number of unmanned commercial hydrothermal plants already employ.
An advantage of an HDR reservoir is that its confined nature makes it highly suitable for load-following operations, whereby the rate of energy production is varied to meet the varying demand for electric power—a process that can greatly increase the economic competitiveness of the technology. [113]
In 1986 the HDR system project of France and Germany in Soultz-sous-Forêts was started. In 1991 wells were drilled to 2.2 km depth and were stimulated. However, the attempt to create a reservoir was unsuccessful as high water losses was observed. [114] [8]
In 1995 wells were deepened to 3.9 km and stimulated. A reservoir was created successfully in 1997 and a four-month circulation test with 25 L/s (6.6 USgal/s) flow rate without water loss was attained. [8]
In 2003 wells were deepened to 5.1 km. Stimulations were done to create a third reservoir, during circulation tests in 2005-2008 water was produced at a temperature of about 160 °C with low water loss. Construction of a power plant was begun. [115] The power plant started to produce electricity in 2016, it was installed with a gross capacity of 1.7 MWe. [116]
There have been numerous reports of the testing of unconfined geothermal systems pressure-stimulated in crystalline basement rock: for instance at the Rosemanowes quarry in Cornwall, England; [117] at the Hijiori [118] and Ogachi [119] calderas in Japan; and in the Cooper Basin, Australia. [120] However, all these “engineered” geothermal systems, while developed under programs directed toward the investigation of HDR technologies, have proven to be open—as evidenced by the high water losses observed during pressurized circulation. [121] In essence, they are all EGS or hydrothermal systems, not true HDR reservoirs.
The EGS concept was first described by Los Alamos researchers in 1990, at a geothermal symposium sponsored by the United States Department of Energy (DOE) [122] —many years before the DOE coined the term EGS in an attempt to emphasize the geothermal aspect of heat mining rather than the unique characteristics of HDR.
Hot Wet Rock (HWR) hydrothermal technology makes use of hot fluids found naturally in basement rock; but such HWR conditions are rare. [123] By far the bulk of the world's geothermal resource base (over 98%) is in the form of basement rock that is hot but dry—with no naturally available water. This means that HDR technology is applicable almost everywhere on Earth (hence the claim that HDR geothermal energy is ubiquitous). On the other hand, an uneconomic resource is actually just energy storage and not useful.
Typically, the temperature in those vast regions of the accessible crystalline basement rock increases with depth. This geothermal gradient, which is the principal HDR resource variable, ranges from less than 20 °C/km to over 60 °C/km, depending upon location. The concomitant HDR economic variable is the cost of drilling to depths at which rock temperatures are sufficiently high to permit the development of a suitable reservoir. [124] The advent of new technologies for drilling hard crystalline basement rocks, such as new PDC (polycrystalline diamond compact) drill bits, drilling turbines or fluid-driven percussive technologies (such as Mudhammer [125] ) may significantly improve HDR economics in the near future.[ citation needed ]
A definitive book on HDR development, including a full account of the experiments at Fenton Hill, was published by Springer-Verlag in April 2012. [105]
Geothermal energy is thermal energy extracted from the Earth's crust. It combines energy from the formation of the planet and from radioactive decay. Geothermal energy has been exploited as a source of heat and/or electric power for millennia.
Induced seismicity is typically earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth's crust. Most induced seismicity is of a low magnitude. A few sites regularly have larger quakes, such as The Geysers geothermal plant in California which averaged two M4 events and 15 M3 events every year from 2004 to 2009. The Human-Induced Earthquake Database (HiQuake) documents all reported cases of induced seismicity proposed on scientific grounds and is the most complete compilation of its kind.
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 since the heat is mostly needed in the winter.
Supercritical carbon dioxide is a fluid state of carbon dioxide where it is held at or above its critical temperature and critical pressure.
A binary cycle is a method for generating electrical power from geothermal resources and employs two separate fluid cycles, hence binary cycle. The primary cycle extracts the geothermal energy from the reservoir, and secondary cycle converts the heat into work to drive the generator and generate electricity.
Steam-assisted gravity drainage is an enhanced oil recovery technology for producing heavy crude oil and bitumen. It is an advanced form of steam stimulation in which a pair of horizontal wells are drilled into the oil reservoir, one a few metres above the other. High pressure steam is continuously injected into the upper wellbore to heat the oil and reduce its viscosity, causing the heated oil to drain into the lower wellbore, where it is pumped out. Dr. Roger Butler, engineer at Imperial Oil from 1955 to 1982, invented the steam assisted gravity drainage (SAGD) process in the 1970s. Butler "developed the concept of using horizontal pairs of wells and injected steam to develop certain deposits of bitumen considered too deep for mining". In 1983 Butler became director of technical programs for the Alberta Oil Sands Technology and Research Authority (AOSTRA), a crown corporation created by Alberta Premier Lougheed to promote new technologies for oil sands and heavy crude oil production. AOSTRA quickly supported SAGD as a promising innovation in oil sands extraction technology.
Petroleum is a fossil fuel that can be drawn from beneath the Earth's surface. Reservoirs of petroleum are formed through the mixture of plants, algae, and sediments in shallow seas under high pressure. Petroleum is mostly recovered from oil drilling. Seismic surveys and other methods are used to locate oil reservoirs. Oil rigs and oil platforms are used to drill long holes into the earth to create an oil well and extract petroleum. After extraction, oil is refined to make gasoline and other products such as tires and refrigerators. Extraction of petroleum can be dangerous and have led to oil spills.
Rosemanowes Quarry, near Penryn, Cornwall, England, was a granite quarry and the site of an early experiment in extracting geothermal energy from the earth using hot dry rock (HDR) technology.
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.
Geothermal energy was first used for electric power production in the United States in 1960. The Geysers in Sonoma and Lake counties, California was developed into the largest geothermal steam electrical plant in the world, at 1,517 megawatts. Other geothermal steam fields operate in the western US and Alaska.
The Geysers is the world's largest geothermal field, containing a complex of 18 geothermal power plants, drawing steam from more than 350 wells, located in the Mayacamas Mountains approximately 72 miles (116 km) north of San Francisco, California.
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, while geothermal heating is in use in 70 countries.
Canada has substantial potential for geothermal energy development. To date, development has all been for heating applications. Canada has 103,523 direct use installations as of 2013. There is currently no electricity being generated from geothermal sources in Canada although substantial potential exists in the Canadian Cordillera. The most advanced project exists as a test geothermal-electrical site at the Mount Meager massif in British Columbia, where a 100 MegaWatt (MW) facility could be developed. Potential for enhanced geothermal energy systems (EGS) exists throughout Canada. There are six geothermal power and two direct use projects listed with the Canadian Geothermal Energy Association.
The Iceland Deep Drilling Project (IDDP) is a geothermal project established in 2000 by a consortium of the National Energy Authority of Iceland (Orkustofnun/OS) and four of Iceland's leading energy companies: Hitaveita Suðurnesja (HS), Landsvirkjun, Orkuveita Reykjavíkur and Mannvit Engineering. The consortium is referred to as "Deep Vision".
AltaRock Energy Inc. is a privately held corporation that focuses on the development of geothermal energy resources and enhanced geothermal systems (EGS). It is headquartered in Seattle, Washington and has a technology development office in Sausalito, California. AltaRock has filed patent applications and holds exclusive licenses for related intellectual property related to EGS. In 2008 it started its first project near The Geysers in California to demonstrate the ability of EGS to be a reliable, renewable and clean source for the production of electric power.
United Downs Deep Geothermal Power is the United Kingdom's first geothermal electricity project. It is situated near Redruth in Cornwall, England. It is owned and operated by Geothermal Engineering (GEL), a private UK company. The drilling site is on the United Downs industrial estate, chosen for its geology, existing grid connection, proximity to access roads and limited impact on local communities. Energy is extracted by cycling water through a naturally hot reservoir and using the heated water to drive a turbine to produce electricity and for direct heating. The company plans to begin delivering electricity (2MMe) and heat (<10MWth) in 2024. A lithium resource was discovered in the well.
Induced seismicity in Basel led to suspension of its hot dry rock enhanced geothermal systems project. A seismic-hazard evaluation was then conducted, resulting in the cancellation of the project in December 2009. Basel, Switzerland sits atop a historically active fault and most of the city was destroyed in a magnitude 6.5 earthquake in 1356. But the Basel project, although it had established an operational approach for addressing induced earthquakes, had not performed a thorough seismic risk assessment before starting geothermal stimulation.
Geothermal exploration is the exploration of the subsurface in search of viable active geothermal regions with the goal of building a geothermal power plant, where hot fluids drive turbines to create electricity. Exploration methods include a broad range of disciplines including geology, geophysics, geochemistry and engineering.
Solar augmented geothermal energy (SAGE) is an advanced method of geothermal energy that creates a synthetic geothermal storage resource by heating a natural brine with solar energy and adding enough heat when the sun shines to generate power 24 hours a day. The earth is given enough energy in one hour to provide all electrical needs for a year. Available energy is not the issue, but energy storage is the problem and SAGE creates effective storage and electrical power delivery on demand. This technology is especially effective for geothermal wells that have demonstrated inconsistent heat or idle oil or gas fields that have demonstrated the proper geology and have an abundance of solar.
Frontier Observatory for Research in Geothermal Energy (FORGE) is a US government program supporting research into geothermal energy. The FORGE site is near Milford, Utah, funded for up to $140 million. As of 2023, numerous test wells had been drilled, and flux measurements had been conducted, but energy production had not commenced.
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