Geothermal power

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,^[1][2] while geothermal heating is in use in 70 countries.^[3]

Krafla, a geothermal power station in Iceland

Countries with installed and/or developing geothermal power projects

As of 2019, worldwide geothermal power capacity amounts to 15.4 gigawatts (GW), of which 23.9% (3.68 GW) are installed in the United States.^[4] International markets grew at an average annual rate of 5 percent over the three years to 2015, and global geothermal power capacity is expected to reach 14.5–17.6 GW by 2020.^[5] Based on current geologic knowledge and technology the Geothermal Energy Association (GEA) publicly discloses, the GEA estimates that only 6.9% of total global potential has been tapped so far, while the IPCC reported geothermal power potential to be in the range of 35 GW to 2 TW.^[3] Countries generating more than 15 percent of their electricity from geothermal sources include El Salvador, Kenya, the Philippines, Iceland, New Zealand,^[6] and Costa Rica. Indonesia has an estimated potential of 29 GW of geothermal energy resources, the largest in the world; in 2017, its installed capacity was 1.8 GW.

Geothermal power is considered to be a sustainable, renewable source of energy because the heat extraction is small compared with the Earth's heat content.^[7] The greenhouse gas emissions of geothermal electric stations average 45 grams of carbon dioxide per kilowatt-hour of electricity, or less than 5% of those of conventional coal-fired plants.^[8]

As a source of renewable energy for both power and heating, geothermal has the potential to meet 3 to 5% of global demand by 2050. With economic incentives, it is estimated that by 2100 it will be possible to meet 10% of global demand with geothermal power.^[6]

History and development

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.^[9] 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.

 

Trends in the top five geothermal electricity-generating countries, 1980–2012 (US EIA)

 

Global geothermal electric capacity. Upper red line is installed capacity;^[10] lower green line is realized production.^[3]

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.^[11] 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.^[6]

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.^[12] The original turbine lasted for more than 30 years and produced 11 MW net power.^[13]

The binary cycle power station was first demonstrated in 1967 in the Soviet Union and later introduced to the United States in 1981,^[12] 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 °C (135 °F).^[14]

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.^[15] 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.^[16]

The thermal efficiency of geothermal electric stations is low, around 7–10%,^[17] 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]} 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.^[18] However the global average capacity factor was 74.5% in 2008, according to the IPCC.^[19]

Resources

 

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

The Earth's heat content is about 1×10¹⁹ TJ (2.8×10¹⁵ TWh).^[3] This heat naturally flows to the surface by conduction at a rate of 44.2 TW^[20] and is replenished by radioactive decay at a rate of 30 TW.^[7] 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 25–30 °C per kilometre (km) of depth in most of the world, so wells would have to be several kilometres deep to permit electricity generation.^[3] 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.^[15] 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.^[15]

Estimates of the electricity generating potential of geothermal energy vary from 35 to 2000 GW depending on the scale of investments.^[3] 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.^[15] The MIT report estimated that over 200×10⁹ TJ (200 ZJ; 5.6×10⁷ TWh) 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.^[15]

At present, geothermal wells are rarely more than 3 km (1.9 mi) deep.^[3] Upper estimates of geothermal resources assume wells as deep as 10 km (6.2 mi). 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 12.261 km (7.619 mi) deep.^[21] Wells drilled to depths greater than 4 km (2.5 mi) generally incur drilling costs in the tens of millions of dollars.^[22] 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.^[7] 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,^[23] and at the Geysers field in California since 1960.^[24]

Power station types

 

 

 

Dry steam (left), flash steam (centre), and binary cycle (right) power stations.

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 power stations

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.^[25] At these sites, there may be liquid water present in the reservoir, but only steam, not water, is produced to the surface.^[25] Dry steam power directly uses geothermal steam of 150 °C or greater to turn turbines.^[3] As the turbine rotates it powers a generator that produces electricity and adds to the power field.^[26] Then, the steam is emitted to a condenser, where it turns back into a liquid, which then cools the water.^[27] 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.^[28]

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 °C, usually more. This is the most common type of station in operation today.^{[citation needed]} Flash steam plants use geothermal reservoirs of water with temperatures greater than 360 °F (182 °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.^{[29] [30]}

Binary cycle power stations

Main article: Binary cycle

Binary cycle power stations are the most recent development, and can accept fluid temperatures as low as 57 °C.^[14] 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.^[31] Both Organic Rankine and Kalina cycles are used. The thermal efficiency of this type of station is typically about 10–13%.^[32] 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.^[33]

Worldwide production

 

Installed geothermal energy capacity, 2022^[34]

 

Cracks at the historic Town Hall of Staufen im Breisgau presumed due to damage from geothermal drilling

 

A geothermal power station in Negros Oriental, Philippines

 

Geothermal power center in the Usulután Department, El Salvador

The International Renewable Energy Agency has reported that 14,438 megawatts (MW) of geothermal power was online worldwide at the end of 2020, generating 94,949 GWh of electricity. ^[35] 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.^[36]

In 2021, the United States led the world in geothermal electricity production with 3,889 MW of installed capacity, a substantial increase from 2020 when it produced 2,587 MW. Indonesia follows the US as the second highest producer of geothermal power in the world, with 2,277 MW of capacity online in 2021.

Al Gore said in The Climate Project Asia Pacific Summit that Indonesia could become a super power country in electricity production from geothermal energy.^[37] 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.^[38]

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.^[39]

The geography of Japan is uniquely 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.^[40]

Utility-grade stations

See also: List of geothermal power stations

 

Yearly geothermal generation by continent^[41]

 

Geothermal generation by country, 2021^[41]

The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California, United States.^[42] As of 2021, five countries (Kenya, Iceland, El Salvador, New Zealand, and Nicaragua) generate more than 15% of their electricity from geothermal sources.^[41]

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.^[41] Only includes countries with more than 0.01 TWh of generation. Links for each location go to the relevant geothermal power page, when available.

Country	Gen (TWh)	% gen.	Cap. (GW)	% cap. growth	Cap. fac.
World	91.80	0.3%	14.67	1.7	71%
United States	16.24	0.4%	2.60	1.0	71%
Indonesia	15.90	5.2%	2.28	6.9	80%
Philippines	10.89	10.1%	1.93	0	64%
Turkey	10.77	3.4%	1.68	3.9	73%
New Zealand	7.82	18.0%	1.27	0	70%
Iceland	5.68	29.4%	0.76	0	86%
Italy	5.53	2.0%	0.77	0	82%
Kenya	5.12	43.4%	0.86	0	68%
Mexico	4.28	1.3%	1.03	0	47%
Japan	3.02	0.3%	0.48	0	72%
Costa Rica	1.60	12.6%	0.26	0	70%
El Salvador	1.58	23.9%	0.20	0	88%
Nicaragua	0.78	16.9%	0.15	0	58%
Russia	0.45	0.04%	0.07	0	69%
Papua New Guinea	0.40	8.2%	0.06	0	82%
Chile	0.33	0.4%	0.04	0	94%
Guatemala	0.32	2.2%	0.05	0	73%
Honduras	0.31	2.6%	0.04	0	91%
Germany	0.25	0.04%	0.05	15.0	62%
Portugal	0.18	0.4%	0.03	0	70%
France	0.13	0.03%	0.02	0	95%
China	0.13	0.002%	0.03	0	55%
Croatia	0.07	0.5%	0.01	0	85%

Environmental impact

 

The 120-MW_e Nesjavellir power station in southwest Iceland

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 CO
₂ equivalent emissions per megawatt-hour of generated electricity (kg CO
₂eq/MW·h). For comparison, a coal-fired power plant emits 1,001 kg of CO
₂ equivalent per megawatt-hour when not coupled with carbon capture and storage (CCS).^[8] 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.^[43]

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^[43] and in the CarbFix project in Iceland.

Other stations like the Kızıldere geothermal power plant, exhibit the capability to utilize geothermal fluids to process carbon dioxide gas into dry ice at two nearby plants resulting in very little environmental impact.^[44]

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.^[45] 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.^[46] 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.^[47] 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 GW·h versus 3,632 and 1,335 square meters for coal facilities and wind farms respectively.^[46] They use 20 litres of freshwater per MW·h versus over 1000 litres per MW·h for nuclear, coal, or oil.^[46]

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.

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.^[48]

While volcanic activity produces geothermal energy, it is also risky. As of 2022^[update] the Puna Geothermal Venture has still not returned to full capacity after the 2018 lower Puna eruption.^[49]

Economics

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 megawatts (MW) of electricity generation and costs about $10 million to drill, with a 20% failure rate.^[22] 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 kW·h.^[10] Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4 million per MW and levelized costs above $0.054 per kW·h in 2007.^[50]

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.^[51][52]

Geothermal power is highly scalable: a small power station can supply a rural village, though initial capital costs can be high.^[53]

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.^[54]

See also

•  Renewable energy portal
•  Energy portal

• 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

References

1. Geothermal Energy Association. Geothermal Energy: International Market Update 25 May 2017 at the Wayback Machine May 2010, p. 4-6.
2. Bassam, Nasir El; Maegaard, Preben; Schlichting, Marcia (2013). Distributed Renewable Energies for Off-Grid Communities: Strategies and Technologies Toward Achieving Sustainability in Energy Generation and Supply. Newnes. p. 187. ISBN 978-0-12-397178-4. from the original on 11 May 2021. Retrieved 25 October 2020.
3. Fridleifsson, Ingvar B.; Bertani, Ruggero; Huenges, Ernst; Lund, John W.; Ragnarsson, Arni; Rybach, Ladislaus (11 February 2008). O. Hohmeyer and T. Trittin (ed.). The possible role and contribution of geothermal energy to the mitigation of climate change (PDF). IPCC Scoping Meeting on Renewable Energy Sources. Luebeck, Germany. pp. 59–80. Retrieved 27 August 2022.
4. Richter, Alexander (27 January 2020). "The Top 10 Geothermal Countries 2019 – based on installed generation capacity (MWe)". Think GeoEnergy - Geothermal Energy News. from the original on 26 January 2021. Retrieved 19 February 2021.
5. "The International Geothermal Market At a Glance – May 2015" (PDF). GEA—Geothermal Energy Association. May 2015. (PDF) from the original on 6 October 2021. Retrieved 23 November 2021.
6. Craig, William; Gavin, Kenneth (2018). Geothermal Energy, Heat Exchange Systems and Energy Piles. London: ICE Publishing. pp. 41–42. ISBN 9780727763983. from the original on 21 August 2018. Retrieved 21 August 2018.
7. Rybach, Ladislaus (September 2007), "Geothermal Sustainability" (PDF), Geo-Heat Centre Quarterly Bulletin, vol. 28, no. 3, Klamath Falls, Oregon: Oregon Institute of Technology, pp. 2–7, ISSN 0276-1084, (PDF) from the original on 17 February 2012, retrieved 9 May 2009
8. Moomaw, W., P. Burgherr, G. Heath, M. Lenzen, J. Nyboer, A. Verbruggen, 2011: Annex II: Methodology. In IPCC: Special Report on Renewable Energy Sources and Climate Change Mitigation (ref. page 10) 27 June 2013 at the Wayback Machine
9. Tiwari, G. N.; Ghosal, M. K. Renewable Energy Resources: Basic Principles and Applications. Alpha Science Int'l Ltd., 2005 ISBN 1-84265-125-0
10. Bertani, Ruggero (September 2007), "World Geothermal Generation in 2007" (PDF), Geo-Heat Centre Quarterly Bulletin, vol. 28, no. 3, Klamath Falls, Oregon: Oregon Institute of Technology, pp. 8–19, ISSN 0276-1084, (PDF) from the original on 17 February 2012, retrieved 12 April 2009
11. . IPENZ Engineering Heritage. Archived from Wairakei Geothermal Power Development the original on 22 June 2013. Retrieved 4 February 2023. {{cite web}}: Check |url= value (help)
12. Lund, J. (September 2004), "100 Years of Geothermal Power Production" (PDF), Geo-Heat Centre Quarterly Bulletin, vol. 25, no. 3, Klamath Falls, Oregon: Oregon Institute of Technology, pp. 11–19, ISSN 0276-1084, (PDF) from the original on 17 June 2010, retrieved 13 April 2009
13. McLarty, Lynn; Reed, Marshall J. (October 1992), "The U.S. Geothermal Industry: Three Decades of Growth" (PDF), Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 14 (4), London: Taylor & Francis: 443–455, doi:10.1080/00908319208908739, archived from the original (PDF) on 16 May 2016, retrieved 29 July 2013
14. Erkan, K.; Holdmann, G.; Benoit, W.; Blackwell, D. (2008), "Understanding the Chena Hot Springs, Alaska, geothermal system using temperature and pressure data", Geothermics, 37 (6): 565–585, doi:10.1016/j.geothermics.2008.09.001, ISSN 0375-6505
15. Tester, Jefferson W.; et al., The Future of Geothermal Energy (PDF), Impact, vol. of Enhanced Geothermal Systems (Egs) on the United States in the 21st Century: An Assessment, Idaho Falls: Idaho National Laboratory, ISBN 0-615-13438-6, archived from the original (PDF) on 10 March 2011, retrieved 7 February 2007
16. Bertani, Ruggero (2009). "Geothermal Energy: An Overview on Resources and Potential" (PDF). Proceedings of the International Conference on National Development of Geothermal Energy Use. Slovakia. (PDF) from the original on 16 July 2011. Retrieved 28 May 2010.
17. Schavemaker, Pieter; van der Sluis, Lou (2008). Electrical Power Systems Essentials. John Wiley & Sons, Ltd. ISBN 978-0470-51027-8.
18. Lund, John W. (2003), "The USA Geothermal Country Update", Geothermics, European Geothermal Conference 2003, 32 (4–6), Elsevier Science Ltd.: 409–418, Bibcode:2003Geoth..32..409L, doi:10.1016/S0375-6505(03)00053-1
19. Goldstein, B., G. Hiriart, R. Bertani, C. Bromley, L. Gutiérrez-Negrín, E. Huenges, H. Muraoka, A. Ragnarsson, J. Tester, V. Zui (2011) "Geothermal Energy" 5 June 2012 at the Wayback Machine. 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.
20. Pollack, H.N.; S. J. Hurter, and J. R. Johnson; Johnson, Jeffrey R. (1993), "Heat Flow from the Earth's Interior: Analysis of the Global Data Set", Rev. Geophys., vol. 30, no. 3, pp. 267–280, Bibcode:1993RvGeo..31..267P, doi:10.1029/93RG01249, from the original on 3 March 2012, retrieved 1 November 2009
21. "Kola". www.icdp-online.org. ICDP. from the original on 27 May 2018. Retrieved 27 May 2018.
22. (PDF), New York: Glacier Partners, October 2009, archived from the original (PDF) on 21 May 2013, retrieved 17 October 2009
23. Thain, Ian A. (September 1998), (PDF), Geo-Heat Centre Quarterly Bulletin, vol. 19, no. 3, Klamath Falls, Oregon: Oregon Institute of Technology, pp. 1–4, ISSN 0276-1084, archived from the original (PDF) on 14 June 2011, retrieved 2 June 2009
24. Axelsson, Gudni; Stefánsson, Valgardur; Björnsson, Grímur; Liu, Jiurong (April 2005), "Sustainable Management of Geothermal Resources and Utilization for 100 – 300 Years" (PDF), Proceedings World Geothermal Congress 2005, International Geothermal Association, retrieved 27 August 2022
25. Tabak, John (2009). Solar and Geothermal Energy. New York: Facts On File, Inc. pp. 97–183. ISBN 978-0-8160-7086-2.
26. "Geothermal Energy". National Geographic. National Geographic Society. 20 November 2012. from the original on 11 November 2020. Retrieved 9 March 2018.
27. Gawell, Karl (June 2014). "Economic Costs and Benefits of Geothermal Power" (PDF). Geothermal Energy Association. (PDF) from the original on 18 November 2017. Retrieved 9 March 2018.
28. The Future of Energy: Earth, Wind and Fire. Scientific American. 8 April 2013. pp. 160–. ISBN 978-1-4668-3386-9. from the original on 8 May 2019. Retrieved 20 December 2016.
29. . US DOE EERE. Archived from the original on 6 December 2010. Retrieved 4 February 2023.
30. . Environment. 19 October 2009. Archived from the original on 8 January 2021. Retrieved 4 February 2023.
31. . Office of Energy Efficiency and Renewable Energy. Archived from the original on 4 October 2008. Retrieved 1 October 2008.
32. DiPippo, Ronald (2016). Geothermal Power Plants (4th ed.). Butterworth-Heinemann. p. 203. ISBN 978-0-08-100879-9.
33. Tomarov, G. V.; Shipkov, A. A. (1 April 2017). "Modern geothermal power: Binary cycle geothermal power plants". Thermal Engineering. 64 (4): 243–250. Bibcode:2017ThEng..64..243T. doi:10.1134/S0040601517040097. ISSN 1555-6301. S2CID 255304218.
34. "Installed geothermal energy capacity". Our World in Data. Retrieved 15 August 2023.
35. "Renewable Energy Statistics 2022". /publications/2022/Jul/Renewable-Energy-Statistics-2022. 18 July 2022. Retrieved 22 October 2022.
36. Fouad Saad (2016). The Shock of Energy Transition. Partridge Publishing Singapore. ISBN 9781482864953.
37. antaranews.com. . Antara News. Archived from the original on 5 June 2019. Retrieved 4 February 2023.
38. "India's 1st geothermal power plant to come up in Chhattisgarh". Economic Times. 17 February 2013. Archived from the original on 15 May 2016. Retrieved 4 February 2023.
39. Morphet, Suzanne (March–April 2012), , Innovation Magazine (Journal of the Association of Professional Engineers and Geoscientists of BC): 22, archived from the original on 27 July 2012, retrieved 5 April 2012
40. Carol Hager; Christoph H. Stefes, eds. (2017). Germany's Energy Transition: A Comparative Perspective. Palgrave Macmillan US. p. 191. ISBN 9781137442888.
41. 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. "International". eia.gov. Retrieved 2 January 2024.
42. Kagel, Alyssa; Diana Bates; Karl Gawell. A Guide to Geothermal Energy and the Environment (PDF). Geothermal Energy Association. Retrieved 9 February 2014.
43. Wannan, Olivia (13 August 2022). "Geothermal energy is already reliable - soon it might be carbon-neutral, too". Stuff.co.nz. Retrieved 14 August 2022.
44. Dipippo, Ronald (2012). Ph.D. Massachusetts; Dartmouth: Elsevier Ltd. pp. 437–438. ISBN 9780080982069.
45. Bargagli1, R.; Cateni, D.; Nelli, L.; Olmastroni, S.; Zagarese, B. (August 1997), "Environmental Impact of Trace Element Emissions from Geothermal Power Plants", Environmental Contamination Toxicology, 33 (2), New York: 172–181, doi:10.1007/s002449900239, PMID 9294245, S2CID 30238608{{citation}}: CS1 maint: numeric names: authors list (link)
46. Lund, John W. (June 2007), "Characteristics, Development and utilization of geothermal resources" (PDF), Geo-Heat Centre Quarterly Bulletin, vol. 28, no. 2, Klamath Falls, Oregon: Oregon Institute of Technology, pp. 1–9, ISSN 0276-1084, (PDF) from the original on 17 June 2010, retrieved 16 April 2009
47. Deichmann, N.; Mai, M.; Bethmann, F.; Ernst, J.; Evans, K.; Fäh, D.; Giardini, D.; Häring, M.; Husen, S.; Kästli, P.; Bachmann, C.; Ripperger, J.; Schanz, U.; Wiemer, S. (2007), "Seismicity Induced by Water Injection for Geothermal Reservoir Stimulation 5 km Below the City of Basel, Switzerland", American Geophysical Union, Fall Meeting, 53: V53F–08, Bibcode:2007AGUFM.V53F..08D
48. Дядькин, Ю. Д. (2001). "Извлечение и использование тепла земли". Горный информационно-аналитический бюллетень (научно-технический журнал). from the original on 27 January 2021. Retrieved 3 October 2020.
49. Penn, Ivan (31 May 2022). "Stung by High Energy Costs, Hawaii Looks to the Sun". The New York Times. p. B1. ISSN 0362-4331. Retrieved 31 May 2022.
50. Sanyal, Subir K.; Morrow, James W.; Butler, Steven J.; Robertson-Tait, Ann (22 January 2007). "Cost of Electricity from Enhanced Geothermal Systems" (PDF). Proc. Thirty-Second Workshop on Geothermal Reservoir Engineering. Stanford, California. (PDF) from the original on 18 April 2008. Retrieved 1 November 2009.
51. Brahambhatt, Rupendra (9 September 2022). "In a world first, scientists propose geothermal power plants that also work as valuable clean energy reservoirs". interestingengineering.com. Retrieved 20 October 2022.
52. Ricks, Wilson; Norbeck, Jack; Jenkins, Jesse (1 May 2022). "The value of in-reservoir energy storage for flexible dispatch of geothermal power". Applied Energy. 313: 118807. doi:10.1016/j.apenergy.2022.118807. ISSN 0306-2619. S2CID 247302205.
    • University press release: Waters, Sharon. "Study shows geothermal could be an ideal energy storage technology". Princeton University via techxplore.com. Retrieved 20 October 2022.
53. Lund, John W.; Boyd, Tonya (June 1999), "Small Geothermal Power Project Examples" (PDF), Geo-Heat Centre Quarterly Bulletin, vol. 20, no. 2, Klamath Falls, Oregon: Oregon Institute of Technology, pp. 9–26, ISSN 0276-1084, (PDF) from the original on 14 June 2011, retrieved 2 June 2009
54. (Press release). Reuters. Archived from the original on 14 November 2012. Retrieved 14 October 2009.

External links

• Articles on Geothermal Energy 26 October 2020 at the Wayback Machine
• The Geothermal Collection by the University of Hawaii at Manoa
• GRC Geothermal Library