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|image1=Krafla geothermal power station wiki.jpg
|image2=World map of geothermal power countries installed and developing.svg
|caption1=[[Krafla Geothermal Power Station|Krafla]], a geothermal power station in Iceland
|caption2=Countries with installed and/or developing geothermal power projects
}}
{{Sustainable energy}}


'''Geothermal power''' is [[electricity generation|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 24 countries,<ref name=gea2010/> while [[geothermal heating]] is in use in 70 countries.<ref name="IPCC"/>

As of 2015, worldwide geothermal power capacity amounts to 12.8 [[gigawatt]]s (GW), of which 28 percent or 3,548 megawatts are installed in the [[Geothermal energy in the United States|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&nbsp;GW by 2020.<ref>{{cite web |url=http://geo-energy.org/reports/2015/Int'lMarketataGlanceMay2015Final5_14_15.pdf |title=The International Geothermal Market At a Glance – May 2015 |publisher=GEA—Geothermal Energy Association |date=May 2015}}</ref> Based on current geologic knowledge and technology the GEA publicly discloses, the [[Geothermal Energy Association]] (GEA) estimates that only 6.5 percent of total global potential has been tapped so far, while the [[IPCC]] reported geothermal power potential to be in the range of 35&nbsp;GW to 2&nbsp;[[terawatt|TW]].<ref name="IPCC" /> Countries generating more than 15 percent of their electricity from geothermal sources include [[Geothermal power in El Salvador|El Salvador]], [[Geothermal power in Kenya|Kenya]], the [[Geothermal power in the Philippines|Philippines]], [[Geothermal power in Iceland|Iceland]] and [[Costa Rica]].

Geothermal power is considered to be a [[sustainability|sustainable]], [[renewable energy|renewable]] source of energy because the heat extraction is small compared with the [[Earth's internal heat budget|Earth's heat content]].<ref name="sustainability" /> The [[Life-cycle greenhouse-gas emissions of energy sources|greenhouse gas emissions]] of geothermal electric stations are on average 45&nbsp;grams of [[carbon dioxide]] per kilowatt-hour of electricity, or less than 5 percent of that of conventional coal-fired plants.<ref name="IPCC Annex II">Moomaw, W., P. Burgherr, G. Heath, M. Lenzen, J. Nyboer, A. Verbruggen, [http://srren.ipcc-wg3.de/report/IPCC_SRREN_Annex_II.pdf 2011: Annex II: Methodology. In IPCC: Special Report on Renewable Energy Sources and Climate Change Mitigation (ref. page 10)]</ref>

== History and development ==
In the 20th&nbsp;century, demand for electricity led to the consideration of geothermal power as a generating source. [[Piero Ginori Conti|Prince Piero Ginori Conti]] tested the first geothermal power generator on 4 July 1904 in [[Larderello]], Italy. It successfully lit four light bulbs.<ref>Tiwari, G. N.; Ghosal, M. K. ''Renewable Energy Resources: Basic Principles and Applications.'' Alpha Science Int'l Ltd., 2005 {{ISBN|1-84265-125-0}}</ref> Later, in 1911, the world's first commercial geothermal power station 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.

[[File:Top 5 Geothermal-Electric Countries.png|thumb|left|Trends in the top five geothermal electricity-generating countries, 1980–2012 (US EIA)]]
[[File:geothermal capacity.svg|thumb|left|Global geothermal electric capacity. Upper red line is installed capacity;<ref name="Bertani"/> lower green line is realized production.<ref name="IPCC" />]]

In 1958, New Zealand became the second major industrial producer of geothermal electricity when its [[Wairakei Power Station|Wairakei station]] was commissioned. Wairakei was the first station to use flash steam technology.<ref>[http://www.ipenz.org.nz/heritage/itemdetail.cfm?itemid=84 IPENZ Engineering Heritage]. Ipenz.org.nz. Retrieved 13 December 2013.</ref>

In 1960, [[Pacific Gas and Electric]] began operation of the first successful geothermal electric power station in the United States at The Geysers in California.<ref name="100years" /> The original turbine lasted for more than 30&nbsp;years and produced 11&nbsp;[[Megawatt|MW]] net power.<ref>
{{Citation
|last1=McLarty |first1=Lynn
|last2=Reed |first2=Marshall J.
|title=The U.S. Geothermal Industry: Three Decades of Growth
|journal=Energy Sources, Part A: Recovery, Utilization, and Environmental Effects
|volume=14
|issue=4
|pages=443–455
|publisher=Taylor & Francis
|location=London
|date=October 1992
|url=http://geotherm.inel.gov/publications/articles/mclarty/mclarty-reed.pdf| doi = 10.1080/00908319208908739
}}</ref>

The binary cycle power station was first demonstrated in 1967 in Russia and later introduced to the USA in 1981,<ref name="100years">{{Citation
|last =Lund |first=J.
|date=September 2004
|title=100 Years of Geothermal Power Production
|periodical=Geo-Heat Centre Quarterly Bulletin
|publication-place =Klamath Falls, Oregon
|publisher=Oregon Institute of Technology
|volume=25
|issue=3
|pages=11–19
|url=http://geoheat.oit.edu/bulletin/bull25-3/art2.pdf
|issn=0276-1084
|accessdate=13 April 2009
}}</ref> 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 station in [[Chena Hot Springs, Alaska]], came on-line, producing electricity from a record low fluid temperature of 57&nbsp;°C (135&nbsp;°F).<ref name="Chena"/>

Geothermal electric stations have until recently been built exclusively where high temperature geothermal resources are available near the surface. The development of [[binary cycle power plant]]s and improvements in drilling and extraction technology may enable [[enhanced geothermal systems]] over a much greater geographical range.<ref name="INEL" /> 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 [[Geothermal power in Australia|Australia]], the [[United Kingdom]], and the [[United States of America]].<ref>
{{cite web
|first = Ruggero |last=Bertani
|title=Geothermal Energy: An Overview on Resources and Potential
|url=http://pangea.stanford.edu/ERE/pdf/IGAstandard/ISS/2009Slovakia/I.1.Bertani.pdf
|series=Proceedings of the International Conference on National Development of Geothermal Energy Use
|year=2009
|place=Slovakia
}}</ref>

The [[thermal efficiency]] of geothermal electric stations is low, around 7–10%,<ref>{{cite book|last1=Schavemaker|first1=Pieter|last2=van der Sluis|first2=Lou|title=Electrical Power Systems Essentials|date=2008|publisher=John Wiley & Sons, Ltd|isbn=978-0470-51027-8}}</ref> 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 [[Cycle efficiency|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 station. In order to produce more energy than the pumps consume, electricity generation requires high temperature geothermal fields and specialized heat cycles.{{Citation needed|date=May 2010}} 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.<ref>
{{Citation
|last=Lund |first=John W.
|title=The USA Geothermal Country Update
|journal=Geothermics
|volume=32
|issue=4–6
|pages=409–418
|publisher=Elsevier Science Ltd.
|series=European Geothermal Conference 2003
|year=2003
|doi=10.1016/S0375-6505(03)00053-1
}}</ref> However the global average [[capacity factor]] was 74.5% in 2008, according to the [[IPCC]].<ref>Goldstein, B., G. Hiriart, R. Bertani, C. Bromley, L. Gutiérrez-Negrín, E. Huenges, H. Muraoka, A. Ragnarsson, J. Tester, V. Zui (2011) [http://srren.ipcc-wg3.de/report/IPCC_SRREN_Ch04.pdf "Geothermal Energy"]. In ''IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation'', Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA Geothermal Energy. p. 404.</ref>

== Resources ==
[[File:EGS diagram.svg|thumb|left|'''Enhanced geothermal system''' 1:Reservoir 2:Pump&nbsp;house 3:Heat&nbsp;exchanger 4:Turbine&nbsp;hall 5:Production&nbsp;well 6:Injection&nbsp;well 7:Hot water to district heating 8:Porous&nbsp;sediments 9:Observation&nbsp;well 10:Crystalline&nbsp;bedrock]]
The Earth’s heat content is about [[1 E31 J|{{Convert|1E19|TJ|TWh|lk=off|abbr=on}}]].<ref name="IPCC" /> This heat naturally flows to the surface by conduction at a rate of 44.2 [[terawatts|TW]]<ref name=pollack_et_al>
{{Citation
|last=Pollack |first=H.N.
|author2=S. J. Hurter, and J. R. Johnson
|year=1993
|title=Heat Flow from the Earth's Interior: Analysis of the Global Data Set
|url=http://www.agu.org/pubs/crossref/1993/93RG01249.shtml
|volume=30
|issue=3
|pages=267–280
|periodical=Rev. Geophys.
|doi=10.1029/93RG01249
|bibcode=1993RvGeo..31..267P
|last3=Johnson
|first3=Jeffrey R.
}}</ref> and is replenished by radioactive decay at a rate of 30&nbsp;TW.<ref name="sustainability">
{{Citation
|last=Rybach |first=Ladislaus
|date=September 2007
|title=Geothermal Sustainability
|periodical=Geo-Heat Centre Quarterly Bulletin
|publication-place=Klamath Falls, Oregon
|publisher=Oregon Institute of Technology
|volume=28
|issue=3
|pages=2–7
|url=http://geoheat.oit.edu/bulletin/bull28-3/art2.pdf
|issn=0276-1084
|accessdate=9 May 2009
}}</ref> 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/m<sup>2</sup> on average) to be recoverable. The [[Earth's crust]] effectively acts as a thick insulating blanket which must be pierced by fluid conduits (of [[magma]], 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 conduit]]s, [[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&nbsp;°C per kilometre (km) of depth in most of the world, so wells would have to be several kilometres deep to permit electricity generation.<ref name="IPCC" /> 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.<ref name="INEL" /> 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.<ref name="INEL" />

Estimates of the electricity generating potential of geothermal energy vary from 35 to 2000&nbsp;GW depending on the scale of investments.<ref name="IPCC"/> This does not include non-electric heat recovered by co-generation, geothermal heat pumps and other direct use. A 2006 report by [[MIT|the Massachusetts Institute of Technology]] (MIT) that included the potential of enhanced geothermal systems estimated that investing 1&nbsp;billion US&nbsp;dollars in research and development over 15&nbsp;years would allow the creation of 100&nbsp;GW of electrical generating capacity by 2050 in the United States alone.<ref name="INEL"/> The MIT report estimated that over {{Convert|200E9|TJ|ZJ TWh|abbr=on}} would be extractable, with the potential to increase this to over 2,000&nbsp;ZJ with technology improvements – sufficient to provide all the world's present energy needs for several [[Millennium|millennia]].<ref name="INEL" />

At present, geothermal wells are rarely more than {{convert|3|km|mi|1|abbr=on}} deep.<ref name="IPCC" /> Upper estimates of geothermal resources assume wells as deep as {{convert|10|km|mi|1|abbr=on}}. Drilling near 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]] (KSDB-3), is {{Convert|12.261|km|mi|abbr=on}} deep.<ref name="ICDP_KSDB3">{{cite web|title=Kola|url=https://www.icdp-online.org/projects/world/europe/kola-russia/|website=www.icdp-online.org|publisher=ICDP|accessdate=2018-05-27}}</ref> This record has recently been imitated by commercial oil wells, such as [[Exxon]]'s Z-12 well in the Chayvo field, [[Sakhalin-I|Sakhalin]].<ref>
{{Citation
|last=Watkins
|first=Eric
|title=ExxonMobil drills record extended-reach well at Sakhalin-1
|newspaper=Oil & Gas Journal
|date=11 February 2008
|url=http://www.mapsearch.com/news/display.html?id=319813
|accessdate=31 October 2009
|dead-url=yes
|archiveurl=https://web.archive.org/web/20100305092919/http://www.mapsearch.com/news/display.html?id=319813
|archivedate=2010-03-05}}</ref>
Wells drilled to depths greater than {{convert|4|km|mi|1|abbr=on}} generally incur drilling costs in the tens of millions of dollars.<ref name="econ101" /> 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.<ref name="sustainability" /> 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#Geothermal field|Wairakei]], and the Geysers have all reduced production from their peaks. It is not clear whether these stations 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,<ref name="Wairakei">
{{Citation
|last=Thain |first=Ian A.
|date=September 1998
|title=A Brief History of the Wairakei Geothermal Power Project
|periodical=Geo-Heat Centre Quarterly Bulletin
|publication-place=Klamath Falls, Oregon
|publisher=Oregon Institute of Technology
|volume=19
|issue=3
|pages=1–4
|url=http://geoheat.oit.edu/bulletin/bull19-3/art1.pdf
|issn=0276-1084
|accessdate=2 June 2009
}}</ref> and at The Geysers field in California since 1960.<ref name="300years">
{{Citation
|last1=Axelsson |first1=Gudni
|last2=Stefánsson |first2=Valgardur
|last3=Björnsson |first3=Grímur
|last4=Liu |first4=Jiurong
|date=April 2005
|title=Sustainable Management of Geothermal Resources and Utilization for 100 – 300 Years
|periodical=Proceedings World Geothermal Congress 2005
|publisher=International Geothermal Association
|url=http://iga.igg.cnr.it/geoworld/pdf/WGC/2005/0507.pdf
|accessdate=2 June 2009
}}</ref>

== Power station types ==
{{Multiple image|total_width=750
| image1 = Diagram VaporDominatedGeothermal inturperated version.svg|width1=485|height1=612
| image2 = Diagram HotWaterGeothermal inturperated version.svg|width2=200|height2=255
| image3 = Geothermal Binary System.svg|width3=324|height3=500
| footer = Dry steam (left), flash steam (centre), and binary cycle (right) power stations.
| footer_align = center
}}

Geothermal power stations are similar to other steam turbine [[thermal power station]]s in that heat from a fuel source (in geothermal's case, the Earth's core) is used to heat water or another [[Working fluids|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 stations ===
Dry steam stations are the simplest and oldest design. This type of power station is not found very often, because it requires a resource that produces dry steam, but is the most efficient, with the simplest facilities.<ref>{{cite book|last1=Tabak|first1=John|title=Solar and Geothermal Energy|date=2009|publisher=Facts On File, Inc.|location=New York|isbn=978-0-8160-7086-2|pages=97-183|accessdate=9 March 2018}}</ref> In these sites, there may be liquid water present in the reservoir, but no water is produced to the surface, only steam. <ref>{{cite book|last1=Tabak|first1=John|title=Solar and Geothermal Energy|date=2009|publisher=Facts On File, Inc.|location=New York|isbn=978-0-8160-7086-2|pages=97-183|accessdate=9 March 2018}}</ref> Dry Steam Power directly uses geothermal steam of 150&nbsp;°C or greater to turn turbines.<ref name="IPCC">{{Citation|first1=Ingvar B. |last1=Fridleifsson, |first2=Ruggero |last2=Bertani |first3=Ernst |last3=Huenges |first4=John W. |last4=Lund |first5=Arni |last5=Ragnarsson |first6=Ladislaus |last6=Rybach |date=11 February 2008 |title=The possible role and contribution of geothermal energy to the mitigation of climate change |conference=IPCC Scoping Meeting on Renewable Energy Sources |editor=O. Hohmeyer and T. Trittin |location=Luebeck, Germany |pages=59–80 |url=http://iga.igg.cnr.it/documenti/IGA/Fridleifsson_et_al_IPCC_Geothermal_paper_2008.pdf |format=PDF |accessdate=6 April 2009 |df=dmy }}{{dead link|date=February 2017|bot=medic}}{{cbignore|bot=medic}}</ref> As the turbine rotates it powers a generator which then produces electricity and adds to the power field. <ref>{{cite web|title=Geothermal Energy|url=https://www.nationalgeographic.org/encyclopedia/geothermal-energy/|website=National Geographic|publisher=National Geographic Society|accessdate=9 March 2018}}</ref> Then, the steam is emitted to a condenser. Here the steam turns back into a liquid which then cools the water.<ref>{{cite news|last1=Gawell|first1=Karl|title=Economic Costs and Benefits of Geothermal Power|url=http://geo-energy.org/reports/Economic%20Cost%20and%20Benfits_Publication_6_16.pdf|accessdate=9 March 2018|agency=Geothermal Energy Assosiation|date=June 2014}}</ref> After the water is cooled it flows down a pipe that conducts the condensate back into deep wells, where it can be reheated and produced again. At [[The Geysers]] in California, after the first thirty years of power production, the steam supply had depleted and generation was substantially reduced. To restore some of the former capacity, supplemental water injection was developed during the 1990's and 2000's, including utilization of effluent from nearby municipal sewage treatment facilities.<ref>{{cite book|author=Scientific American Editors|title=The Future of Energy: Earth, Wind and Fire|url=https://books.google.com/books?id=pGfQmBtXYx0C&pg=PT160|date=8 April 2013|publisher=Scientific American|isbn=978-1-4668-3386-9|pages=160–}}</ref>


=== Flash steam power stations ===
Flash steam stations 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&nbsp;°C, usually more. This is the most common type of station in operation today. Flash steam plants use geothermal reservoirs of water with temperatures greater than 360&nbsp;°F (182&nbsp;°C). The hot water flows up through wells in the ground under its own pressure. As it flows upward, the pressure decreases and some of the hot water boils into steam. The steam is then separated from the water and used to power a turbine/generator. Any leftover water and condensed steam may be injected back into the reservoir, making this a potentially sustainable resource.<ref>[http://www1.eere.energy.gov/geothermal/powerplants.html US DOE EERE Hydrothermal Power Systems]. eere.energy.gov (22 February 2012). Retrieved 2013-12-13.</ref>
<ref>[http://environment.nationalgeographic.com/environment/global-warming/geothermal-profile/ Geothermal Energy]. National Geographic.</ref>
=== Binary cycle power stations ===
{{Main|Binary cycle}}
Binary cycle power stations are the most recent development, and can accept fluid temperatures as low as 57&nbsp;°C.<ref name="Chena">
{{Citation
|url=http://linkinghub.elsevier.com/retrieve/pii/S0375650508000576
|title=Understanding the Chena Hot Springs, Alaska, geothermal system using temperature and pressure data
|year=2008
|journal=Geothermics
|pages=565–585
|volume=37
|issue=6
|last1=Erkan |first1=K.
|last2=Holdmann |first2=G.
|last3=Benoit |first3=W.
|last4=Blackwell |first4=D.
|doi=10.1016/j.geothermics.2008.09.001
|issn=0375-6505
|accessdate=11 April 2009
}}</ref> 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 station being constructed today.<ref name="EERE1">{{cite web|url=http://www1.eere.energy.gov/geothermal/geothermal_basics.html|title=Geothermal Basics Overview|publisher=Office of Energy Efficiency and Renewable Energy|accessdate=1 October 2008|deadurl=yes|archiveurl=https://web.archive.org/web/20081004020606/http://www1.eere.energy.gov/geothermal/geothermal_basics.html|archivedate=4 October 2008|df=dmy-all}}</ref> Both [[Organic Rankine]] and [[Kalina cycle]]s are used. The thermal efficiency of this type station is typically about 10–13%.

== Worldwide production ==
[[File:Larderello 001.JPG|thumb|right|250px|[[Larderello]] Geothermal Station, in Italy]]

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.<ref name=gea2010/> This represents a 20% increase in geothermal power online capacity since 2005. IGA projected this would grow to 18,500 MW by 2015, due to the large number of projects that were under consideration, often in areas previously assumed to have little exploitable resource.<ref name=gea2010>Geothermal Energy Association. [http://www.geo-energy.org/pdf/reports/GEA_International_Market_Report_Final_May_2010.pdf Geothermal Energy: International Market Update] May 2010, p. 4-6.</ref>

In 2010, the [[Geothermal energy in the United States|United States]] led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power stations;<ref name=geap7/> the largest group of geothermal [[power plant]]s in the world is located at [[The Geysers]], a geothermal field in [[California]].<ref name="Khan">
{{Citation
|first1 = M. Ali
|last = Khan
|year = 2007
|title = The Geysers Geothermal Field, an Injection Success Story
|series = Annual Forum of the Groundwater Protection Council
|url = http://www.gwpc.org/meetings/forum/2007/proceedings/Papers/Khan,%20Ali%20Paper.pdf
|format = PDF
|accessdate = 25 January 2010
|deadurl = yes
|archiveurl = https://web.archive.org/web/20110726135113/http://www.gwpc.org/meetings/forum/2007/proceedings/Papers/Khan%2C%20Ali%20Paper.pdf
|archivedate = 26 July 2011
|df = dmy-all
}}</ref> 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 27% of the country's electricity generation.<ref name=geap7>Geothermal Energy Association. [http://www.geo-energy.org/pdf/reports/GEA_International_Market_Report_Final_May_2010.pdf Geothermal Energy: International Market Update] May 2010, p. 7.</ref>

[[Al Gore]] said in The Climate Project Asia Pacific Summit that Indonesia could become a super power country in electricity production from geothermal energy.<ref>[http://www.antaranews.com/en/news/1294577958/indonesia-can-be-super-power-on-geothermal-energy-al-gore Indonesia can be super power on geothermal energy : Al Gore]. ANTARA News (9 January 2011). Retrieved 2013-12-13.</ref> India has announced a plan to develop the country's first geothermal power facility in Chhattisgarh.<ref>[http://articles.economictimes.indiatimes.com/2013-02-17/news/37144613_1_geothermal-energy-geothermal-power-plant-national-thermal-power-corporation India's 1st geothermal power plant to come up in Chhattisgarh – Economic Times]. ''The Economic Times''. (17 February 2013). Retrieved 2013-12-13.</ref>

Canada is the only major country on the [[Pacific Ring of Fire]] which has not yet developed geothermal power. The region of greatest potential is the [[Canadian Cordillera]], stretching from [[British Columbia]] to the Yukon, where estimates of generating output have ranged from 1,550 MW to 5,000 MW.<ref>{{Citation| last=Morphet| first=Suzanne| title=Exploring BC's Geothermal Potential| journal=Innovation Magazine (Journal of the Association of Professional Engineers and Geoscientists of BC)|date=March–April 2012| url=http://innovation.digitalityworks.com/issues/2012/MarApr/issue.aspx| page=22}}</ref>

=== Utility-grade stations ===
[[File:Puhagan geothermal plant.jpg|thumb|250px|right|A geothermal power station in [[Negros Oriental]], [[Philippines]].]]

The largest group of geothermal [[power plant]]s in the world is located at [[The Geysers]], a geothermal field in [[California]], [[Geothermal energy in the United States|United States]].<ref name="calpine">
{{cite press release
|title=Calpine Corporation (CPN) (NYSE Arca) Profile
|agency=Reuters
|url=https://www.reuters.com/finance/stocks/companyProfile?rpc=66&symbol=CPN
|accessdate=14 October 2009
}}</ref> As of 2004, five countries ([[Geothermal power in El Salvador|El Salvador]], [[Geothermal power in Kenya|Kenya]], [[Geothermal power in the Philippines|the Philippines]], [[Geothermal power in Iceland|Iceland]], and [[Costa Rica]]) generate more than 15% of their electricity from geothermal sources.<ref name="IPCC" />

Geothermal electricity is generated in the 24 countries listed in the table below. During 2005, contracts were placed for an additional 500 [[Megawatt|MW]] of electrical capacity in the United States, while there were also stations under construction in 11 other countries.<ref name="INEL">
{{Citation
|last=Tester
|first=Jefferson W. ([[Massachusetts Institute of Technology]])
|title=The Future of Geothermal Energy
|volume=of Enhanced Geothermal Systems (Egs) on the United States in the 21st Century: An Assessment
|publisher=Idaho National Laboratory
|location=Idaho Falls
|series=Impact
|isbn=0-615-13438-6
|url=http://geothermal.inel.gov/publications/future_of_geothermal_energy.pdf
|format=PDF
|accessdate=7 February 2007
|displayauthors=etal
}}</ref> 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.

{| style="font-size:95%; text-align:right;" class="wikitable sortable"
|+'''Installed geothermal electric capacity'''
!width=135 |Country
!Capacity (MW)<br>2007<ref name="Bertani">{{Citation| last =Bertani | first =Ruggero| date =September 2007| title =World Geothermal Generation in 2007
| periodical =Geo-Heat Centre Quarterly Bulletin| publication-place =Klamath Falls, Oregon| publisher =Oregon Institute of Technology| volume =28| issue =3| pages =8–19
| url =http://geoheat.oit.edu/bulletin/bull28-3/art3.pdf| issn =0276-1084| accessdate =12 April 2009}}</ref>

!Capacity (MW)<br>2010<ref name="Holm">{{Citation| last =Holm | first =Alison| date =May 2010
| title =Geothermal Energy:International Market Update| publisher =Geothermal Energy Association| page =7
| url =http://www.geo-energy.org/pdf/reports/GEA_International_Market_Report_Final_May_2010.pdf| accessdate =24 May 2010}}</ref>

!Capacity (MW)<br>2013<ref name="Matek">{{Citation| last =Matek | first =Benjamin| date =September 2013
| title =Geothermal Power:International Market Overview| publisher =Geothermal Energy Association| pages =10, 11
| url =http://geo-energy.org/events/2013%20International%20Report%20Final.pdf| accessdate =11 October 2013}}</ref>

!Capacity (MW)<br>2015<ref>Bertani, Ruggero (April 2015) [https://pangea.stanford.edu/ERE/db/WGC/papers/WGC/2015/01001.pdf Geothermal Power Generation in the World 2010–2014 Update Report]. Proceedings World Geothermal Congress 2015, Melbourne, Australia, 19–25 April 2015. pp. 2, 3</ref>
!data-sort-type="number" |Share of national <br/>generation (%)
|-
|align=left| [[Geothermal energy in the United States|USA]] ||2687||3086||3389||3450||0.3
|-
|align=left| [[Geothermal power in the Philippines|Philippines]] ||1969.7||1904||1894||1870||27.0
|-
|align=left| [[Geothermal power in Indonesia|Indonesia]] ||992||1197||1333||1340||3.7
|-
|align=left| [[Geothermal power in Mexico|Mexico]] ||953||958||980||1017||3.0
|-
|align=left| [[Geothermal power in New Zealand|New Zealand]] ||471.6||628||895||1005||14.5<ref name="NZEnergy2013">{{cite web| url=http://www.med.govt.nz/sectors-industries/energy/energy-modelling/publications/energy-in-new-zealand-2014| title=Energy in New Zealand| publisher= New Zealand Ministry of Economic Development| date=September 2014 |accessdate= 22 April 2015}}</ref>
|-
|align=left| [[Geothermal power in Italy|Italy]] ||810.5||843||901||916||1.5
|-
|align=left| [[Geothermal power in Iceland|Iceland]] ||421.2||575||664||665||30.0
|-
|align=left| [[Geothermal power in Kenya|Kenya]] ||128.8||167||215||594||51.0<ref>[https://af.reuters.com/article/investingNews/idAFKBN0LK1AM20150216 Geothermal overtakes hydro as Kenya's main power source in January: KenGen]. Reuters. 16 February 2015</ref>
|-
|align=left| [[Geothermal power in Japan|Japan]] ||535.2||536||537||519||0.1
|-
|align=left| [[Geothermal power in Turkey|Turkey]] ||38||82||163||397||0.3
|-
|align=left| [[Geothermal energy in Costa Rica|Costa Rica]] ||162.5||166||208||207||14.0
|-
|align=left| [[Geothermal energy in El Salvador|El Salvador]] ||204.4||204||204||204||25.0<ref>{{Citation |url=http://www.geothermal-energy.org/229,welcome_to_our_page_with_data_for_el_salvador_-_electricity_generation.html |title=Generacion Electricidad El Salvador |newspaper=IGA |accessdate=30 August 2011 }}</ref><ref>{{Citation |url=http://www.eclac.org/publicaciones/xml/3/43373/2011-021-Mercados_mayoristas_de_electricidad-L1010.pdf |title=CENTROAMÉRICA: MERCADOS MAYORISTAS DE ELECTRICIDAD Y TRANSACCIONES EN EL MERCADO ELÉCTRICO REGIONAL, 2010 |newspaper=CEPAL |accessdate=30 August 2011 }}</ref>
|-
|align=left| [[Electricity sector in Nicaragua|Nicaragua]] ||79||82||97||82||9.9
|-
|align=left| [[Geothermal power in Papua New Guinea|Papua New Guinea]] ||56||56||56||50||
|-
|align=left| [[Geothermal power in Guatemala|Guatemala]] ||53||52||42||52||
|-
|align=left| [[Geothermal power in Portugal|Portugal]] ||23||29||28||29||
|-
|align=left| [[Geothermal power in Russia|Russia]] ||79||79||82||82||
|-
|align=left| [[Geothermal power in China|China]] ||27.8||24||27||27||
|-
|align=left| [[Geothermal power in Germany|Germany]] ||8.4||6.6||13||27||
|-
|align=left| [[Geothermal power in France|France]] ||14.7||16||15||16||
|-
|align=left| [[Geothermal power in Ethiopia|Ethiopia]] ||7.3||7.3||8||7.3||
|-
|align=left| [[Geothermal power in Austria|Austria]] ||1.1||1.4||1||1.2||
|-
|align=left| [[Geothermal power in Australia|Australia]] ||0.2||1.1||1||1.1||
|-
|align=left| [[Geothermal power in Thailand|Thailand]] ||0.3||0.3||0.3||0.3||
|- class="sortbottom"
!Total
!9,731.9||10,709.7||11,765||12,635.9||&ndash;
|}

== Environmental impact ==
[[File:NesjavellirPowerPlant edit2.jpg|thumb|The 120-[[MWe|MW<sub>e</sub>]] [[Nesjavellir Geothermal Power Station|Nesjavellir]] power station in southwest Iceland]]

Fluids drawn from the deep earth carry a mixture of gases, notably [[carbon dioxide]] ({{chem|CO|2|}}), [[hydrogen sulfide]] ({{chem|H|2|S|}}), [[methane]] ({{chem|CH|4|}}), [[ammonia]] ({{chem|NH|3|}}) and [[radon]] ({{chem|Rn|}}). These pollutants contribute to [[global warming]], [[acid rain]], radiation and noxious smells if released.{{not in citation given|date=January 2018}}

Existing geothermal electric stations, that fall within the [[Percentile|50th percentile]] of all total life cycle emissions studies reviewed by the [[IPCC]], produce on average 45&nbsp;kg of {{chem|CO|2|}} equivalent emissions per megawatt-hour of generated electricity (kg {{chem|CO|2|}}eq/[[megawatt-hour|MW·h]]). For comparison, a coal-fired power plant emits 1,001&nbsp;kg of {{chem|CO|2|}} per megawatt-hour when not coupled with [[carbon capture and storage]] (CCS).<ref name="IPCC Annex II" />

Stations that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust. Geothermal stations 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 (element)|mercury]], [[arsenic]], [[boron]], [[antimony]], and salt.<ref name="toxic">
{{Citation
|last1=Bargagli1 |first1=R.
|last2=Cateni |first2=D.
|last3=Nelli |first3 = L.
|last4=Olmastroni |first4=S.
|last5=Zagarese |first5=B.
|title=Environmental Impact of Trace Element Emissions from Geothermal Power Plants
|journal=Environmental Contamination Toxicology
|volume=33
|issue=2
|pages=172–181
|location=New York
|date=August 1997
|doi=10.1007/s002449900239
|pmid=9294245
}}</ref> 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.

Station construction can adversely affect land stability. [[Subsidence]] has occurred in the [[Wairakei field]] in New Zealand.<ref name="utilization">{{Citation
|last=Lund |first=John W.
|date=June 2007
|title=Characteristics, Development and utilization of geothermal resources
|periodical=Geo-Heat Centre Quarterly Bulletin
|publication-place=Klamath Falls, Oregon
|publisher=Oregon Institute of Technology
|volume=28
|issue=2
|pages=1–9
|url=http://geoheat.oit.edu/bulletin/bull28-2/art1.pdf
|issn=0276-1084
|accessdate=16 April 2009
}}</ref> [[Enhanced geothermal systems]] can trigger [[induced seismicity|earthquake]]s due to water injection. 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.<ref>{{Citation |author1=Deichmann, N. |author2=Mai, M. |author3=Bethmann, F. |author4=Ernst, J. |author5=Evans, K. |author6=Fäh, D. |author7=Giardini, D. |author8=Häring, M. |author9=Husen, S. |author10=Kästli, P. |author11=Bachmann, C. |author12=Ripperger, J. |author13=Schanz, U. |author14=Wiemer, S. |title=Seismicity Induced by Water Injection for Geothermal Reservoir Stimulation 5&nbsp;km Below the City of Basel, Switzerland |year=2007 |journal=American Geophysical Union |publisher=American Geophysical Union |bibcode=2007AGUFM.V53F..08D |volume=53 |page=8 }}</ref> The risk of geothermal drilling leading to [[Tectonic uplift|uplift]] has been experienced in [[Staufen im Breisgau]].

Geothermal has minimal land and freshwater requirements. Geothermal stations use 404&nbsp;square&nbsp;meters per&nbsp;[[gigawatt-hour|GW·h]] versus 3,632 and 1,335&nbsp;square&nbsp;meters for coal facilities and wind farms respectively.<ref name="utilization" /> They use 20&nbsp;litres of freshwater per MW·h versus over 1000&nbsp;litres per&nbsp;MW·h for nuclear, coal, or oil.<ref name="utilization" />

Geothermal power stations can also disrupt the natural cycles of geysers. For example, the [[Beowawe, Nevada]] geysers, which were uncapped geothermal wells, stopped erupting due to the development of the dual-flash station.

== 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 [[megawatts]] (MW) of electricity generation and costs about $10 million to drill, with a 20% failure rate.<ref name="econ101">
{{Citation
|date = October 2009
|title = Geothermal Economics 101, Economics of a 35 MW Binary Cycle Geothermal Plant
|publication-place = New York
|publisher = Glacier Partners
|url = http://www.georestore.com/cms_files/Geothermal%20Economics%20101%20-%20Glacier%20Partners.pdf
|accessdate = 17 October 2009
|deadurl = yes
|archiveurl = https://web.archive.org/web/20130521174852/http://www.georestore.com/cms_files/Geothermal%20Economics%20101%20-%20Glacier%20Partners.pdf
|archivedate = 21 May 2013
|df = dmy-all
}}</ref>
In total, electrical station construction and well drilling costs about 2–5&nbsp;million&nbsp;€ per&nbsp;MW of electrical capacity, while the [[levelised energy cost]] is 0.04–0.10&nbsp;€ per&nbsp;kW·h.<ref name="Bertani" /> Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4&nbsp;million per&nbsp;MW and levelized costs above $0.054 per&nbsp;kW·h in 2007.<ref>{{cite web
|first1=Subir K. |last1=Sanyal
|first2=James W. |last2=Morrow
|first3=Steven J. |last3=Butler
|first4=Ann |last4=Robertson-Tait
|title=Cost of Electricity from Enhanced Geothermal Systems
|url=http://pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2007/sanyal1.pdf
|series=Proc. Thirty-Second Workshop on Geothermal Reservoir Engineering
|date=22 January 2007
|place=Stanford, California
}}</ref>

Geothermal power is highly scalable: a small power station can supply a rural village, though initial capital costs can be high.<ref name="small">
{{Citation
|last1=Lund |first1=John W.
|last2=Boyd |first2=Tonya
|date=June 1999
|title=Small Geothermal Power Project Examples
|periodical=Geo-Heat Centre Quarterly Bulletin
|publication-place=Klamath Falls, Oregon
|publisher=Oregon Institute of Technology
|volume=20
|issue=2
|pages=9–26
|url=http://geoheat.oit.edu/bulletin/bull20-2/art2.pdf
|issn=0276-1084
|accessdate=2 June 2009
}}</ref>

The most developed geothermal field is the Geysers in California. In 2008, this field supported 15 stations, all owned by [[Calpine]], with a total generating capacity of 725&nbsp;MW.<ref name="calpine" />

== See also ==
{{Portal|Renewable energy|Energy}}
* [[Geothermal heating]]
* [[Hot dry rock geothermal energy|Enhanced geothermal system]]
* [[Iceland Deep Drilling Project]]
* [[List of renewable energy topics by country|Renewable energy by country]]
{{Clear}}

== References ==
{{Reflist|30em}}

== External links ==
* [http://www.geni.org/globalenergy/library/articles-renewable-energy-transmission/geothermal.shtml Articles on Geothermal Energy]
* [http://scholarspace.manoa.hawaii.edu/handle/10125/21320 The Geothermal Collection by the University of Hawaii at Manoa]
* [https://www.geothermal-library.org/ GRC Geothermal Library]

{{Geothermal power}}
{{Renewable energy by country}}
{{DEFAULTSORT:Geothermal Power}}
{{DEFAULTSORT:Geothermal Power}}
[[Category:Power station technology]]
[[Category:Power station technology]]

Revision as of 09:29, 6 June 2018

it will kill u

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