Geothermal power#Power station types

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

File:geothermal capacity.svg

In 1958, New Zealand became the second major industrial producer of geothermal electricity when its Wairakei station was commissioned. Wairakei was the first station to use flash steam technology.{{cite web |title=IPENZ Engineering Heritage |url=http://www.ipenz.org.nz/heritage/itemdetail.cfm?itemid=84 |url-status=dead |archive-url=https://web.archive.org/web/20130622092009/http://www.ipenz.org.nz/heritage/itemdetail.cfm?itemid=84 |archive-date=22 June 2013 |access-date=February 4, 2023 |publisher=IPENZ Engineering Heritage}} Over the past 60 years, net fluid production has been in excess of 2.5 km³. Subsidence at Wairakei-Tauhara has been an issue in a number of formal hearings related to environmental consents for expanded development of the system as a source of renewable energy.

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.{{Citation |last=Lund |first=J. |title=100 Years of Geothermal Power Production |date=September 2004 |periodical=Geo-Heat Centre Quarterly Bulletin |volume=25 |issue=3 |pages=11–19 |url=http://geoheat.oit.edu/bulletin/bull25-3/art2.pdf |access-date=13 April 2009 |archive-url=https://web.archive.org/web/20100617221828/http://geoheat.oit.edu/bulletin/bull25-3/art2.pdf |archive-date=17 June 2010 |url-status=live |location=Klamath Falls, Oregon |publisher=Oregon Institute of Technology |issn=0276-1084}} The original turbine lasted for more than 30 years and produced 11 MW net power.

{{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

|bibcode= 1992EneSA..14..443M

|access-date= 29 July 2013

|archive-url= http://arquivo.pt/wayback/20160516221028/http://geotherm.inel.gov/publications/articles/mclarty/mclarty%2Dreed.pdf

|archive-date= 16 May 2016

|url-status= dead

|df= dmy-all

}}

An organic fluid based binary cycle power station was first demonstrated in 1967 in the Soviet Union and later introduced to the United States in 1981{{Citation needed|date=September 2024}}, following the 1970s energy crisis and significant changes in regulatory policies. This technology allows the use of temperature resources as low as {{cvt|81|C|F}}. In 2006, a binary cycle station in Chena Hot Springs, Alaska, came on-line, producing electricity from a record low fluid temperature of {{cvt|57|C|F}}.

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 plants and improvements in drilling and extraction technology may enable enhanced geothermal systems over a much greater geographical range.

{{Citation

|last= Tester

|first= Jefferson W.

|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

|access-date= 7 February 2007

|display-authors= etal

|archive-url= https://wayback.archive-it.org/all/20110310030646/http://geothermal.inel.gov/publications/future_of_geothermal_energy.pdf

|archive-date= 10 March 2011

|url-status= dead

|df= dmy-all

}} 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.{{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

|access-date=28 May 2010

|archive-date=16 July 2011

|archive-url=https://web.archive.org/web/20110716082354/http://pangea.stanford.edu/ERE/pdf/IGAstandard/ISS/2009Slovakia/I.1.Bertani.pdf

|url-status=live

}}

The thermal efficiency of geothermal electric stations is low, around 7 to 10%,{{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}} because geothermal fluids are at a low temperature compared with steam from boilers. By the laws of thermodynamics this low temperature limits the efficiency of heat engines in extracting useful energy during the generation of electricity. Exhaust heat is wasted, unless it can be used directly and locally, for example in greenhouses, timber mills, and district heating. The efficiency of the system does not affect operational costs as it would for a coal or other fossil fuel plant, but it does factor into the viability of the 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.

{{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

|bibcode=2003Geoth..32..409L

}} However the global average capacity factor was 74.5% in 2008, according to the IPCC.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"] {{Webarchive|url=https://web.archive.org/web/20120605105149/http://srren.ipcc-wg3.de/report/IPCC_SRREN_Ch04.pdf |date=5 June 2012 }}. 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.

File:EGS diagram.svg

The Earth's heat content is about 1 E31 J. This heat naturally flows to the surface by conduction at a rate of 44.2 TW{{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.

|access-date=1 November 2009

|archive-date=3 March 2012

|archive-url=https://web.archive.org/web/20120303113553/http://www.agu.org/pubs/crossref/1993/93RG01249.shtml

|url-status=live

}} and is replenished by radioactive decay at a rate of 30 TW.{{Citation

|last=Rybach

|first=Ladislaus

|date=September 2007

|title=Geothermal Sustainability

|periodical=Geo-Heat Centre Quarterly Bulletin

|location=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

|access-date=9 May 2009

|archive-date=17 February 2012

|archive-url=https://web.archive.org/web/20120217184740/http://geoheat.oit.edu/bulletin/bull28-3/art2.pdf

|url-status=live

}} These power rates are more than double humanity's current energy consumption from primary sources, but most of this power is too diffuse (approximately 0.1 W/m² on average) to be recoverable. The Earth's crust effectively acts as a thick insulating blanket which must be pierced by fluid conduits (of 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 conduits, hot springs, hydrothermal circulation, oil wells, 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 a hot spring is not available, a well must be drilled into a hot aquifer. Away from tectonic plate boundaries the geothermal gradient is 25 to 30 °C per kilometre (70 to 85 °F per mile) of depth in most of the world, so wells would have to be several kilometres deep to permit electricity generation. The quantity and quality of recoverable resources improves with drilling depth and proximity to tectonic plate boundaries.

In ground that is hot but dry, or where water pressure is inadequate, injected fluid can stimulate production. Developers bore two holes into a candidate site, and fracture the rock between them with explosives or high-pressure water. Then they pump water or liquefied carbon dioxide down one borehole, and it comes up the other borehole as a gas. This approach is called hot dry rock geothermal energy in Europe, or enhanced geothermal systems in North America. Much greater potential may be available from this approach than from conventional tapping of natural aquifers.

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

At present, geothermal wells are rarely more than {{convert|3|km|mi|abbr=on|0}} deep. Upper estimates of geothermal resources assume wells as deep as {{convert|10|km|mi|abbr=on|0}}. 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.{{cite web|title=Kola|url=https://www.icdp-online.org/projects/world/europe/kola-russia/|website=www.icdp-online.org|publisher=ICDP|access-date=2018-05-27|archive-date=27 May 2018|archive-url=https://web.archive.org/web/20180527202146/https://www.icdp-online.org/projects/world/europe/kola-russia/|url-status=live}}

Wells drilled to depths greater than {{convert|4|km|mi|1|abbr=on}} generally incur drilling costs in the tens of millions of dollars. The technological challenges are to drill wide bores at low cost and to break larger volumes of rock.

Geothermal power is considered to be sustainable because the heat extraction is small compared to the Earth's heat content, but extraction must still be monitored to avoid local depletion. Although geothermal sites are capable of providing heat for many decades, individual wells may cool down or run out of water. The three oldest sites, at Larderello, Wairakei, and the Geysers have all reduced production from their peaks. It is not clear whether these 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 Larderello field in Italy since 1913, at the Wairakei field in New Zealand since 1958,{{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

|location=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

|access-date=2 June 2009

|archive-date=14 June 2011

|archive-url=https://web.archive.org/web/20110614115823/http://geoheat.oit.edu/bulletin/bull19-3/art1.pdf

|url-status=dead

}} and at the Geysers field in California since 1960.

{{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= https://www.geothermal-energy.org/pdf/IGAstandard/WGC/2005/0507.pdf

|access-date= 27 August 2022

}}

{{Multiple image|total_width=700

| 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 stations in that heat from a fuel source (in geothermal's case, the Earth's core) is used to heat water or another working fluid. The working fluid is then used to turn a turbine of a generator, thereby producing electricity. The fluid is then cooled and returned to the heat source.

Dry steam stations are the simplest and oldest design. There are few power stations of this type, because they require a resource that produces dry steam, but they are the most efficient, with the simplest facilities.{{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=[https://archive.org/details/solargeothermale00taba_0/page/97 97–183]|url-access=registration|url=https://archive.org/details/solargeothermale00taba_0/page/97}} At these sites, there may be liquid water present in the reservoir, but only steam, not water, is produced to the surface. Dry steam power directly uses geothermal steam of {{cvt|150|C|F|-1}} or greater to turn turbines.{{Cite conference |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=https://www.eartheclipse.com/wp-content/uploads/2016/03/Fridleifsson_et_al_IPCC_Geothermal_paper_2008.pdf |access-date=27 August 2022 |df=dmy}} As the turbine rotates it powers a generator that produces electricity and adds to the power field.{{cite web|title=Geothermal Energy |url= https://education.nationalgeographic.org/resource/geothermal-energy/ |website=National Geographic|publisher=National Geographic Society|access-date=9 March 2018 |date=20 November 2012|archive-date=11 November 2020|archive-url= https://web.archive.org/web/20201111224353/https://www.nationalgeographic.org/encyclopedia/geothermal-energy/|url-status=live}} Then, the steam is emitted to a condenser, where it turns back into a liquid, which then cools the water.{{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|access-date=9 March 2018|agency=Geothermal Energy Association|date=June 2014|archive-date=18 November 2017|archive-url=https://web.archive.org/web/20171118004007/http://geo-energy.org/reports/Economic%20Cost%20and%20Benfits_Publication_6_16.pdf|url-status=live}} 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 30 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 1990s and 2000s, including utilization of effluent from nearby municipal sewage treatment facilities.{{cite book |url={{google books |plainurl=y |id=pGfQmBtXYx0C|page=160}} |title=The Future of Energy: Earth, Wind and Fire |date=8 April 2013 |publisher=Scientific American |isbn=978-1-4668-3386-9 |pages=160– |access-date=20 December 2016 |archive-url=https://web.archive.org/web/20190508102146/https://books.google.com/books?id=pGfQmBtXYx0C&pg=PT160 |archive-date=8 May 2019 |url-status=live}}

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 {{cvt|180|C|F|-1}}, usually more. As of 2022, flash steam stations account for 36.7% of all geothermal power plants and 52.7% of the installed capacity in the world. {{cite journal |last1=Gutiérrez-Negrín |first1=L. C. A. |date=2024-05-12 |title=Evolution of worldwide geothermal power 2020–2023 |journal=Geothermal Energy |language=en |volume=12 |issue=1 |article-number= 14 |publisher=Springer Nature |doi=10.1186/s40517-024-00290-w |doi-access=free |bibcode=2024GeoE...12...14G }} Flash steam plants use geothermal reservoirs of water with temperatures greater than 180 °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 is transformed 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.{{cite web|url=http://www1.eere.energy.gov/geothermal/powerplants.html |title=Hydrothermal Power Systems|publisher=US DOE EERE |archive-url=https://web.archive.org/web/20101206192842/http://www1.eere.energy.gov/geothermal/powerplants.html |archive-date=6 December 2010 |access-date=February 4, 2023}}

{{Cite web |date=2009-10-19 |title=Geothermal Energy Information and Facts |url=https://www.nationalgeographic.com/environment/article/geothermal-energy |access-date=2023-02-04 |website=Environment |language=en|archive-url=https://web.archive.org/web/20210108131328/https://www.nationalgeographic.com/environment/global-warming/geothermal-energy/ |archive-date=8 January 2021 }}

{{Main|Binary cycle}}

Binary cycle power stations are the most recent development, and can accept fluid temperatures as low as {{cvt|57|C|F}}.

{{Citation

|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

}} 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.{{cite web|url=http://www1.eere.energy.gov/geothermal/geothermal_basics.html|title=Geothermal Basics Overview|publisher=Office of Energy Efficiency and Renewable Energy|access-date=1 October 2008|url-status=dead|archive-url=https://web.archive.org/web/20081004020606/http://www1.eere.energy.gov/geothermal/geothermal_basics.html|archive-date=4 October 2008|df=dmy-all}} Both Organic Rankine and Kalina cycles are used. The thermal efficiency of this type of station is typically about 10–13%.{{Cite book |last=DiPippo |first=Ronald |title=Geothermal Power Plants |publisher=Butterworth-Heinemann |year=2016 |isbn=978-0-08-100879-9 |edition=4th |pages=203 |language=English}} Binary cycle power plants have an average unit capacity of 6.3 MW, 30.4 MW at single-flash power plants, 37.4 MW at double-flash plants, and 45.4 MW at power plants working on superheated steam.{{Cite journal |last1=Tomarov |first1=G. V. |last2=Shipkov |first2=A. A. |date=2017-04-01 |title=Modern geothermal power: Binary cycle geothermal power plants |url=https://doi.org/10.1134/S0040601517040097 |journal=Thermal Engineering |language=en |volume=64 |issue=4 |pages=243–250 |doi=10.1134/S0040601517040097 |bibcode=2017ThEng..64..243T |s2cid=255304218 |issn=1555-6301}}

File:Installed geothermal energy capacity.png

File:Staufen.Cracks.jpg presumed due to damage from geothermal drilling]]

File:Puhagan geothermal plant.jpg, Philippines]]

File:Central Geotérmica de Berlín 05.JPG, El Salvador]]

The International Renewable Energy Agency has reported that 14,438 MW of geothermal power was online worldwide at the end of 2020, generating 94,949 GWh of electricity.{{Cite web |title=Renewable Energy Statistics 2022 |url=https://www.irena.org/publications/2022/Jul/Renewable-Energy-Statistics-2022 |access-date=2022-10-22 |website=/publications/2022/Jul/Renewable-Energy-Statistics-2022 |date=18 July 2022 }} In theory, the world's geothermal resources are sufficient to supply humans with energy. However, only a tiny fraction of the world's geothermal resources can at present be explored on a profitable basis.{{Cite book|title= The Shock of Energy Transition | author1=Fouad Saad |publisher=Partridge Publishing Singapore |year=2016 |isbn= 9781482864953 | pages=}}

Al Gore said in The Climate Project Asia Pacific Summit that Indonesia could become a super power country in electricity production from geothermal energy.{{Cite web |last=antaranews.com |title=Indonesia can be super power on geothermal energy : Al Gore |date=9 January 2011 |url=https://en.antaranews.com/news/66789/indonesia-can-be-super-power-on-geothermal-energy--al-gore |access-date=2023-02-04 | publisher=Antara News|archive-url=https://web.archive.org/web/20190605051500/https://en.antaranews.com/news/66789/indonesia-can-be-super-power-on-geothermal-energy--al-gore |archive-date=5 June 2019 }} In 2013 the publicly owned electricity sector in India announced a plan to develop the country's first geothermal power facility in the landlocked state of Chhattisgarh.{{cite web|url=http://articles.economictimes.indiatimes.com/2013-02-17/news/37144613_1_geothermal-energy-geothermal-power-plant-national-thermal-power-corporation |title=India's 1st geothermal power plant to come up in Chhattisgarh |publisher=Economic Times |archive-url=http://arquivo.pt/wayback/20160515131851/http://articles.economictimes.indiatimes.com/2013-02-17/news/37144613_1_geothermal-energy-geothermal-power-plant-national-thermal-power-corporation |archive-date=15 May 2016 |date=17 February 2013|access-date=4 February 2023}}

Geothermal power in Canada has high potential due to its position on the Pacific Ring of Fire. 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.{{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 |access-date=5 April 2012 |archive-url=https://web.archive.org/web/20120727040857/http://innovation.digitalityworks.com/issues/2012/MarApr/issue.aspx |archive-date=27 July 2012 |url-status=dead |df=dmy-all}}

The geography of Japan is uniquely{{weasel inline|date=December 2024}} suited for geothermal power production. Japan has numerous hot springs that could provide fuel for geothermal power plants, but a massive investment in Japan's infrastructure would be necessary.{{Cite book|title= Germany's Energy Transition: A Comparative Perspective | editor1=Carol Hager | editor2= Christoph H. Stefes |publisher= Palgrave Macmillan US |year=2017 |isbn=9781137442888 | pages=191}}

{{see also|List of geothermal power stations}}

File:World geo generation yearly.png

File:World geothermal generation 2021.png

The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California, United States.{{cite book|last=Kagel|first=Alyssa|title=A Guide to Geothermal Energy and the Environment|publisher=Geothermal Energy Association|url=http://geo-energy.org/reports/environmental%20guide.pdf|author2=Diana Bates |author3=Karl Gawell |access-date=February 9, 2014}} As of 2021, five countries (Kenya, Iceland, El Salvador, New Zealand, and Nicaragua) generate more than 15% of their electricity from geothermal sources.

The following table lists these data for each country:

• total generation from geothermal in terawatt-hours,
• percent of that country's generation that was geothermal,
• total geothermal capacity in gigawatts,
• percent growth in geothermal capacity, and
• the geothermal capacity factor for that year.

Data are for the year 2021. Data are sourced from the EIA.Under "Electricity" select "More Electricity data". At the top right, under Generation select 'Total' and 'Geothermal' and under Capacity select 'Geothermal'. Choose the two most recent years. {{cite web |url = https://www.eia.gov/international/data/world |title = International |website = eia.gov |access-date = 2 Jan 2024}} Only includes countries with more than 0.01 TWh of generation. Links for each location go to the relevant geothermal power page, when available.

{{sticky header}}{{table alignment}}{{static row numbers}}{{sort under}}

File:NesjavellirPowerPlant edit2.jpg Nesjavellir power station in southwest Iceland]]

{{Renewable energy sources}}

Existing geothermal electric stations that fall within the 50th percentile of all total life cycle emissions studies reviewed by the IPCC produce on average 45 kg of {{chem|CO|2|}} equivalent emissions per megawatt-hour of generated electricity (kg {{chem|CO|2|}}eq/MWh).{{cite journal | url=https://doi.org/10.1016/j.renene.2024.120552 | doi=10.1016/j.renene.2024.120552 | title=Assessment of the geothermal potential zone of India utilizing GIS-based multi-criteria decision analysis technique | date=2024 | last1=Chouhan | first1=Avinash Kumar | last2=Kumar | first2=Rakesh | last3=Mishra | first3=Abhishek Kumar | journal=Renewable Energy | volume=227 | bibcode=2024REne..22720552C }} For comparison, a coal-fired power plant emits 1,001 kg of {{chem|CO|2|}} equivalent per megawatt-hour when not coupled with carbon capture and storage (CCS). As many geothermal projects are situated in volcanically active areas that naturally emit greenhouse gases, it is hypothesized that geothermal plants may actually decrease the rate of de-gassing by reducing the pressure on underground reservoirs.{{cite web |last1=Wannan |first1=Olivia |title=Geothermal energy is already reliable - soon it might be carbon-neutral, too |url=https://www.stuff.co.nz/environment/climate-news/129520035/geothermal-energy-is-already-reliable--soon-it-might-be-carbonneutral-too |website=Stuff.co.nz |access-date=14 August 2022 |language=en |date=13 August 2022}}

Stations that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust. Geothermal stations can also inject these gases back into the earth as a form of carbon capture and storage, such as in New Zealand and in the CarbFix project in Iceland.

Other stations, like the Kızıldere geothermal power plant, exhibit the capability to use geothermal fluids to process carbon dioxide gas into dry ice at two nearby plants, resulting in very little environmental impact.{{Cite book|last=Dipippo|first=Ronald|title=Ph.D.|publisher=Elsevier Ltd|year=2012|isbn=9780080982069|location=Massachusetts; Dartmouth|pages=437–438}}

In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic chemicals, such as mercury, arsenic, boron, antimony, and salt.

{{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

|bibcode=1997ArECT..33..172B

|s2cid=30238608

}} 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.{{Citation

|last=Lund

|first=John W.

|date=June 2007

|title=Characteristics, Development and utilization of geothermal resources

|periodical=Geo-Heat Centre Quarterly Bulletin

|location=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

|access-date=16 April 2009

|archive-date=17 June 2010

|archive-url=https://web.archive.org/web/20100617215822/http://geoheat.oit.edu/bulletin/bull28-2/art1.pdf

|url-status=live

}} Enhanced geothermal systems can trigger earthquakes 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.{{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 km Below the City of Basel, Switzerland |year=2007 |journal=American Geophysical Union, Fall Meeting |bibcode=2007AGUFM.V53F..08D |volume=53 |pages=V53F–08 }} The risk of geothermal drilling leading to uplift has been experienced in Staufen im Breisgau.

Geothermal has minimal land and freshwater requirements. Geothermal stations use 404 square meters per GWh versus 3,632 and 1,335 square meters for coal facilities and wind farms respectively. They use 20 litres of freshwater per MWh versus over 1000 litres per MWh for nuclear, coal, or oil.

Local climate cooling is possible as a result of the work of the geothermal circulation systems. However, according to an estimation given by Leningrad Mining Institute in 1980s, possible cool-down will be negligible compared to natural climate fluctuations.{{cite journal|last1=Дядькин|first1=Ю. Д.|date=2001|title=Извлечение и использование тепла земли|url=https://cyberleninka.ru/article/n/izvlechenie-i-ispolzovanie-tepla-zemli|journal=Горный информационно-аналитический бюллетень (научно-технический журнал)|access-date=3 October 2020|archive-date=27 January 2021|archive-url=https://web.archive.org/web/20210127050707/https://cyberleninka.ru/article/n/izvlechenie-i-ispolzovanie-tepla-zemli|url-status=live}}

While volcanic activity produces geothermal energy, it is also risky. {{as of|2022}} the Puna Geothermal Venture has still not returned to full capacity after the 2018 lower Puna eruption.{{Cite news |last=Penn |first=Ivan |date=2022-05-31 |title=Stung by High Energy Costs, Hawaii Looks to the Sun |language=en-US |page=B1 |work=The New York Times |url=https://www.nytimes.com/2022/05/30/business/hawaii-solar-energy.html |access-date=2022-05-31 |issn=0362-4331}}

{{See also|Cost of electricity by source}}

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 MW of electricity generation and costs about $10 million to drill, with a 20% failure rate.

{{Citation

|date= October 2009

|title= Geothermal Economics 101, Economics of a 35 MW Binary Cycle Geothermal Plant

|location= New York

|publisher= Glacier Partners

|url= http://www.georestore.com/cms_files/Geothermal%20Economics%20101%20-%20Glacier%20Partners.pdf

|access-date= 17 October 2009

|url-status= usurped

|archive-url= https://web.archive.org/web/20130521174852/http://www.georestore.com/cms_files/Geothermal%20Economics%20101%20-%20Glacier%20Partners.pdf

|archive-date= 21 May 2013

|df= dmy-all

}}

In total, electrical station construction and well drilling costs about 2–5 million € per MW of electrical capacity, while the levelised energy cost is 0.04–0.10 € per kWh. Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4 million per MW and levelized costs above $0.054 per kWh in 2007.{{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

|access-date=1 November 2009

|archive-date=18 April 2008

|archive-url=https://web.archive.org/web/20080418210431/http://pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2007/sanyal1.pdf

|url-status=live

}}

Research suggests in-reservoir storage could increase the economic viability of enhanced geothermal systems in energy systems with a large share of variable renewable energy sources.{{cite news |last1=Brahambhatt |first1=Rupendra |title=In a world first, scientists propose geothermal power plants that also work as valuable clean energy reservoirs |url=https://interestingengineering.com/science/geothermal-power-plants-clean-energy-reservoirs |access-date=20 October 2022 |work=interestingengineering.com |date=9 September 2022}}{{cite journal |last1=Ricks |first1=Wilson |last2=Norbeck |first2=Jack |last3=Jenkins |first3=Jesse |title=The value of in-reservoir energy storage for flexible dispatch of geothermal power |journal=Applied Energy |date=1 May 2022 |volume=313 |pages=118807 |doi=10.1016/j.apenergy.2022.118807 |s2cid=247302205 |url=https://zenodo.org/record/6385742 |language=en |issn=0306-2619|doi-access=free |bibcode=2022ApEn..31318807R }}

• University press release: {{cite news |last1=Waters |first1=Sharon |title=Study shows geothermal could be an ideal energy storage technology |url=https://techxplore.com/news/2022-09-geothermal-ideal-energy-storage-technology.html |access-date=20 October 2022 |work=Princeton University via techxplore.com |language=en}}

Geothermal power is highly scalable: a small power station can supply a rural village, though initial capital costs can be high.{{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

|location=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

|access-date=2 June 2009

|archive-date=14 June 2011

|archive-url=https://web.archive.org/web/20110614115853/http://geoheat.oit.edu/bulletin/bull20-2/art2.pdf

|url-status=live

}}

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 MW.

{{cite press release

|title=Calpine Corporation (CPN) (NYSE Arca) Profile

|publisher=Reuters

|url=https://www.reuters.com/finance/stocks/companyProfile?rpc=66&symbol=CPN

|archive-url=https://web.archive.org/web/20121114114321/http://www.reuters.com/finance/stocks/companyProfile?rpc=66&symbol=CPN

|url-status=dead

|archive-date=14 November 2012

|access-date=14 October 2009

}}

{{Portal|Renewable energy|Energy}}

• Enhanced geothermal system
• Geothermal heating
• Hot dry rock geothermal energy
• Iceland Deep Drilling Project
• List of renewable energy topics by country
• Ocean thermal energy conversion
• Thermal battery
• Renewable white hydrogen - renewable hydrogen produced from using the Earth's mantle

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{{Reflist|30em}}

• [https://www.geni.org/globalenergy/library/articles-renewable-energy-transmission/geothermal.shtml Articles on Geothermal Energy] {{Webarchive|url=https://web.archive.org/web/20201026130618/https://www.geni.org/globalenergy/library/articles-renewable-energy-transmission/geothermal.shtml |date=26 October 2020 }}
• [https://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}}

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