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==Environmental impact==
Water requirements for PSH are small:<ref name=":1">{{Cite journal |last1=Blakers |first1=Andrew |last2=Stocks |first2=Matthew |last3=Lu |first3=Bin |last4=Cheng |first4=Cheng |date=2021-03-25 |title=A review of pumped hydro energy storage |journal=Progress in Energy |volume=3 |issue=2 |pages=022003 |doi=10.1088/2516-1083/abeb5b |bibcode=2021PrEne...3b2003B |s2cid=233653750 |issn=2516-1083|doi-access=free |hdl=1885/296928 |hdl-access=free }}</ref> about 1 gigalitre of initial fill water per gigawatt-hour of storage. This water is recycled uphill and back downhill between the two reservoirs for many decades, but evaporation losses (beyond what rainfall and any inflow from local waterways provide) must be replaced. Land requirements are also small: about 10 hectares per gigawatt-hour of storage,<ref name=":1" /> which is much smaller than the land occupied by the solar and windfarms that the storage might support. Closed loop (off-river) pumped hydro storage has the smallest carbon emissions<ref>{{Cite web |last=Colthorpe |first=Andy |date=2023-08-21 |title=NREL: Closed-loop pumped hydro 'smallest emitter' among energy storage technologies |url=https://www.energy-storage.news/nrel-closed-loop-pumped-hydro-smallest-emitter-among-energy-storage-technologies/ |access-date=2023-08-26 |website=Energy-Storage.News |language=en-US}}</ref> per unit of storage of all candidates for large-scale energy storage.
== Potential technologies ==▼
===Seawater===▼
Pumped storage plants can operate with seawater, although there are additional challenges compared to using fresh water, such as saltwater corrosion and barnacle growth.<ref>{{cite Q|Q107212803}}</ref> Inaugurated in 1966, the 240 MW [[Rance Tidal Power Station|Rance tidal power station]] in France can partially work as a pumped-storage station. When high tides occur at off-peak hours, the turbines can be used to pump more seawater into the reservoir than the high tide would have naturally brought in. It is the only large-scale power plant of its kind.▼
In 1999, the 30 MW [[Okinawa Yanbaru Seawater Pumped Storage Power Station|Yanbaru project]] in Okinawa was the first demonstration of seawater pumped storage. It has since been decommissioned. A 300 MW seawater-based Lanai Pumped Storage Project was considered for Lanai, Hawaii, and seawater-based projects have been proposed in Ireland.<ref>{{Cite web |date=18 February 2012 |title=Massive Energy Storage, Courtesy of West Ireland |url=https://www.science.org/content/article/massive-energy-storage-courtesy-west-ireland |url-status=live |archive-url=https://web.archive.org/web/20170908034315/http://www.sciencemag.org/news/2012/02/massive-energy-storage-courtesy-west-ireland |archive-date=8 September 2017 |access-date=21 June 2017 |website=sciencemag.org}}</ref> A pair of proposed projects in the [[Atacama Desert]] in northern Chile would use 600 MW of photovoltaic solar (Skies of Tarapacá) together with 300 MW of pumped storage (Mirror of Tarapacá) lifting seawater {{convert|600|m}} up a coastal cliff.<ref>{{Cite web |date=11 March 2015 |title=Project Espejo de Tarapacá |url=http://valhalla.cl/espejo-de-tarapaca/ |url-status=live |archive-url=https://web.archive.org/web/20170618160703/http://valhalla.cl/espejo-de-tarapaca/ |archive-date=18 June 2017 |access-date=19 June 2017 |website=Valhalla}}</ref><ref>{{Cite web |date=4 May 2016 |title=The Mirror of Tarapaca: Chilean power project harnesses both sun and sea |url=https://www.power-technology.com/features/featurethe-mirror-of-tarapaca-chilean-power-project-harnesses-both-sun-and-sea-4872272/ |url-status=live |archive-url=https://web.archive.org/web/20190504012539/https://www.power-technology.com/features/featurethe-mirror-of-tarapaca-chilean-power-project-harnesses-both-sun-and-sea-4872272/ |archive-date=4 May 2019 |access-date=4 May 2019}}</ref>▼
===Freshwater coastal reservoirs===▼
Freshwater from the river floods is stored in the sea area replacing seawater by constructing [[coastal reservoir]]s. The stored river water is pumped to uplands by constructing a series of embankment canals and pumped storage hydroelectric stations for the purpose of energy storage, irrigation, industrial, municipal, rejuvenation of exploited rivers, etc. These multipurpose coastal reservoir projects offer massive pumped-storage hydroelectric potential to utilize variable and intermittent solar and wind power that are carbon-neutral, clean, and renewable energy sources.<ref>{{Cite journal |last=Sasidhar |first=Nallapaneni |date=May 2023 |title=Multipurpose Freshwater Coastal Reservoirs and Their Role in Mitigating Climate Change |url=https://www.ijee.latticescipub.com/wp-content/uploads/papers/v3i1/A1842053123.pdf |access-date=2023-05-23 |journal=Indian Journal of Environment Engineering |issn=2582-9289 |volume=3 |issue=1|pages=30–45 |doi=10.54105/ijee.A1842.053123 |s2cid=258753397 }}</ref>▼
===Underground reservoirs===▼
The use of underground reservoirs has been investigated.<ref>{{Cite book |last=Pummer |first=Elena |url=http://publications.rwth-aachen.de/record/667419/files/667419.pdf |title=Hybrid Modelling of the Hydrodynamic Processes in Underground Pumped Storage Plants |publisher=RWTH Aachen University |year=2016 |location=Aachen, Germany |access-date=19 May 2020 |archive-url=https://web.archive.org/web/20201104044602/http://publications.rwth-aachen.de/record/667419/files/667419.pdf |archive-date=4 November 2020 |url-status=live}}</ref> Recent examples include the proposed Summit project in [[Norton, Ohio]], the proposed Maysville project in [[Kentucky]] (underground limestone mine), and the Mount Hope project in [[New Jersey]], which was to have used a former iron mine as the lower reservoir. The proposed energy storage at the [[Callio]] site in [[Pyhäjärvi]] ([[Finland]]) would utilize the deepest base metal mine in Europe, with {{Convert|1450|m|ft}} elevation difference.<ref>{{Cite news |title=Energy storage |language=en-US |work=Callio Pyhäjärvi |url=https://callio.info/energy-storage/opportunities/ |url-status=live |access-date=2018-03-14 |archive-url=https://web.archive.org/web/20180315050701/https://callio.info/energy-storage/opportunities/ |archive-date=15 March 2018}}</ref> Several new underground pumped storage projects have been proposed. Cost-per-kilowatt estimates for these projects can be lower than for surface projects if they use existing underground mine space. There are limited opportunities involving suitable underground space, but the number of underground pumped storage opportunities may increase if abandoned coal mines prove suitable.<ref>{{Cite web |date=17 March 2017 |title=German Coal Mine to Be Reborn as Giant Pumped Storage Hydro Facility |url=http://www.renewableenergyworld.com/articles/2017/03/german-coal-mine-to-be-reborn-as-giant-pumped-storage-hydro-facility.html |url-status=live |archive-url=https://web.archive.org/web/20190709081435/https://www.renewableenergyworld.com/articles/2017/03/german-coal-mine-to-be-reborn-as-giant-pumped-storage-hydro-facility.html |archive-date=9 July 2019 |access-date=20 March 2017}}</ref>▼
In [[Bendigo]], Victoria, Australia, the Bendigo Sustainability Group has proposed the use of the old gold mines under Bendigo for Pumped Hydro Energy Storage.<ref>{{Cite web |last=Smith |first=Trevor |title=Bendigo Mines Pumped Hydro Project |url=https://www.bsg.org.au/bendigo-pumped-hydro-project/ |url-status=live |archive-url=https://web.archive.org/web/20180715235943/https://www.bsg.org.au/bendigo-pumped-hydro-project/ |archive-date=15 July 2018 |access-date=2020-07-13 |website=Bendigo Sustainability Group |language=en-AU}}</ref> Bendigo has the greatest concentration of deep shaft hard rock mines anywhere in the world with over 5,000 shafts sunk under Bendigo in the second half of the 19th Century. The deepest shaft extends 1,406 metres vertically underground. A recent pre-feasibility study has shown the concept to be viable with a generation capacity of 30 MW and a run time of 6 hours using a water head of over 750 metres.▼
US-based start-up Quidnet Energy is exploring using abandoned oil and gas wells for pumped storage. If successful they hope to scale up, utilizing some of the 3 million abandoned wells in the US.<ref>{{Cite news |last=Lo |first=Chris |date=27 November 2016 |title=Could depleted oil wells be the next step in energy storage? |url=https://www.power-technology.com/analysis/featurecould-depleted-oil-wells-be-the-next-step-in-energy-storage-5680002/ |access-date=16 May 2022}}</ref><ref>{{Cite web |title=Press Release: CPS Energy & Quidnet Energy Announce Landmark Agreement to Build Grid-Scale, Long Duration, Geomechanical Pumped Storage Project in Texas |url=https://www.quidnetenergy.com/news/2022/03/cps-energy--quidnet-energy-announce-landmark-agreement-to-build-gridscale-long-duration-geomechanical-pumped-storage-project-in-texas/ |access-date=16 May 2022 |website=quidnetenergy.com}}</ref>▼
===Decentralised systems===▼
Small (or micro) applications for pumped storage could be built on streams and within infrastructures, such as drinking water networks<ref>{{Cite web |title=Senator Wash |url=http://www.iid.com/water/water-transportation-system/colorado-river-facilities/senator-wash |url-status=live |archive-url=https://web.archive.org/web/20160626043856/http://www.iid.com/water/water-transportation-system/colorado-river-facilities/senator-wash |archive-date=26 June 2016 |access-date=6 August 2016 |website=www.iid.com |publisher=Imperial Irrigation District |language=en}}</ref> and artificial snow-making infrastructures. In this regard, a storm-water basin has been concretely implemented as a cost-effective solution for a water reservoir in a micro-pumped hydro energy storage.<ref name=":1a" /> Such plants provide distributed [[energy storage]] and distributed flexible [[electricity production]] and can contribute to the decentralized integration of [[intermittent renewable energy]] technologies, such as [[wind power]] and [[solar power]]. Reservoirs that can be used for small pumped-storage hydropower plants could include<ref name="Thesis">{{Cite book |last=Crettenand |first=N. |url=https://infoscience.epfl.ch/record/176337?ln=en |title=The facilitation of mini and small hydropower in Switzerland: shaping the institutional framework. With a particular focus on storage and pumped-storage schemes |publisher=Ecole Polytechnique Fédérale de Lausanne |year=2012 |archive-url=https://web.archive.org/web/20180913040049/https://infoscience.epfl.ch/record/176337?ln=en |archive-date=13 September 2018 |type=PhD Thesis N° 5356.}}</ref> natural or artificial lakes, reservoirs within other structures such as irrigation, or unused portions of mines or underground military installations. In [[Switzerland]] one study suggested that the total installed capacity of small pumped-storage hydropower plants in 2011 could be increased by 3 to 9 times by providing adequate [[Market-based environmental policy instruments|policy instruments]].<ref name="Thesis" />▼
===Underwater reservoirs===▼
{{Further|Stored Energy at Sea}}▼
In March 2017, the research project StEnSea (Storing Energy at Sea) announced their successful completion of a four-week test of a pumped storage underwater reservoir. In this configuration, a hollow sphere submerged and anchored at great depth acts as the lower reservoir, while the upper reservoir is the enclosing body of water. Electricity is created when water is let in via a reversible turbine integrated into the sphere. During off-peak hours, the turbine changes direction and pumps the water out again, using "surplus" electricity from the grid. ▼
The quantity of power created when water is let in, grows proportionally to the height of the column of water above the sphere. In other words: the deeper the sphere is located, the more densely it can store energy.▼
As such, the energy storage capacity of the submerged reservoir is not governed by the [[gravitational energy]] in the traditional sense, but by the [[vertical pressure variation]].▼
===Home use===▼
Using a pumped-storage system of [[cistern]]s and small generators, [[pico hydro]] may also be effective for "closed loop" home energy generation systems.<ref name="sciencedaily">{{Cite web |date=2016-10-24 |title=Is energy storage via pumped hydro systems is possible on a very small scale? |url=https://www.sciencedaily.com/releases/2016/10/161024090454.htm |archive-url=https://web.archive.org/web/20170510054924/https://www.sciencedaily.com/releases/2016/10/161024090454.htm |archive-date=2017-05-10 |access-date=6 September 2018 |website=Science Daily}}</ref><ref name="homepower">{{Cite news |last=Root |first=Ben |date=December 2011 – January 2012 |title=Microhydro Myths & Misconceptions |volume=146 |page=77 |publisher=Home Power |url=https://www.homepower.com/articles/microhydro-power/design-installation/microhydro-myths-misconceptions |access-date=6 September 2018 |archive-url=https://web.archive.org/web/20180905214822/https://www.homepower.com/articles/microhydro-power/design-installation/microhydro-myths-misconceptions |archive-date=5 September 2018}}</ref>▼
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===Hydraulic Fracturing===▼
Using [[hydraulic fracturing]] pressure can be stored underground in [[Permeability_(Earth_sciences)|impermeable]] strata such as shale.<ref>{{cite journal|title= Is Hydraulic Fracturing the Next Big Breakthrough in Battery Tech?|journal= [[Society_of_Petroleum_Engineers#Magazines|Journal of Petroleum Technology]]|publisher= [[Society of Petroleum Engineers]]|volume= 75|number =10|date =October 2023|pages= 36–41|last= Jacobs|first= Trent}}</ref> The shale used contains no hydrocarbons.<ref name="TM91221">{{Cite news |last=Russell Gold |date=September 21, 2021 |title=Fracking Has a Bad Rep, but Its Tech Is Powering a Clean Energy Shift Texas start-ups are harnessing know-how born of the shale boom in pursuit of a greener future. |work=Texas Monthly |url=https://www.texasmonthly.com/news-politics/fracking-clean-energy-geothermal/ |url-status=live |access-date=September 23, 2021 |archive-url=https://web.archive.org/web/20210924171206/https://www.texasmonthly.com/news-politics/fracking-clean-energy-geothermal/ |archive-date=24 September 2021}}</ref>▼
===Electrolysis===▼
One idea to reduce pumping energy requirements is to use [[electrolysis of water|electricity to split water]] at a low elevation, and then pipe the lighter-than-air hydrogen to a high elevation where it could be burned with atmospheric oxygen to produce water. This high-elevation water could then be returned to the low elevation, potentially more than recovering efficiency losses by harvesting the gravitational potential energy of higher-altitude atmospheric oxygen (which is later harmlessly re-mixed by sun-powered wind).<ref>{{cite news |title=Recharging the power grid |page=13 |date=May 2003 |magazine=Technology Review |author=Charles I. Clausing}}</ref>▼
===High-density pumped hydro===▼
RheEnergise<ref name="RheEnergise">[https://www.rheenergise.com/ RheEnergise company website]</ref> aim to improve the efficiency of pumped storage by using fluid 2.5x denser than water ("a fine-milled suspended solid in water"<ref name="IoME article">[https://www.imeche.org/news/news-article/high-density-pumped-hydro-could-be-installed-on-thousands-of-small-hills]Institution of Mechanical Engineers article</ref>), such that "projects can be 2.5x smaller for the same power."<ref name="RheEnergise_how_it_works">[https://www.rheenergise.com/how-it-works] RheEnergise 'how it works' article</ref>▼
== History ==
Line 65 ⟶ 107:
== Worldwide use ==
===Summary===▼
{{See also|List of pumped-storage hydroelectric power stations}}
In 2009, world pumped storage generating capacity was 104 [[
The [[European Union [[Japan]] had 25.5 GW net capacity (24.5% of world capacity).<ref name=eia/> In 2010 the United States had 21.5 [[Watt|GW]] of pumped storage generating capacity (20.6% of world capacity).<ref>{{Cite web |title=Report: An Updated Annual Energy Outlook 2009 Reference Case Reflecting Provisions of the American Recovery and Reinvestment Act and Recent Changes in the Economic Outlook |url=http://www.eia.doe.gov/oiaf/servicerpt/stimulus/excel/aeostimtab_9.xls |archive-url=https://web.archive.org/web/20100528144341/http://www.eia.doe.gov/oiaf/servicerpt/stimulus/excel/aeostimtab_9.xls |archive-date=2010-05-28 |access-date=2010-10-29}}</ref> PSH contributed 21,073 GWh of energy in 2020 in the United States, but −5,321 GWh (net) because more energy is consumed in pumping than is generated.<ref>{{Cite web |title=Table 3.27 Gross/Net Generation by Energy Storage Technology: Total (All Sectors), 2010 - 2020 |url=https://www.eia.gov/electricity/annual/html/epa_03_27.html |url-status=live |archive-url=https://web.archive.org/web/20211115121948/https://www.eia.gov/electricity/annual/html/epa_03_27.html |archive-date=15 November 2021 |access-date=4 January 2022 |publisher=US Energy Information Administration}}</ref> Nameplate pumped storage capacity had grown to 21.6 GW by 2014, with pumped storage comprising 97% of grid-scale energy storage in the United States. As of late 2014, there were 51 active project proposals with a total of 39 GW of new nameplate capacity across all stages of the FERC licensing process for new pumped storage hydroelectric plants in the United States, but no new plants were currently under construction in the United States at the time.<ref>{{Cite web |title=2014 Hydropower Market Report Highlights |url=https://www.energy.gov/sites/prod/files/2015/04/f22/Hydropower-Market-Report-Highlights.pdf |url-status=live |archive-url=https://web.archive.org/web/20170220092655/https://www.energy.gov/sites/prod/files/2015/04/f22/Hydropower-Market-Report-Highlights.pdf |archive-date=20 February 2017 |access-date=19 February 2017 |publisher=U.S. Department of Energy}}</ref><ref>{{Cite web |title=2014 Hydropower Market Report |url=https://www.energy.gov/sites/prod/files/2015/05/f22/2014%20Hydropower%20Market%20Report_20150512_rev6.pdf |url-status=live |archive-url=https://web.archive.org/web/20170201035749/https://energy.gov/sites/prod/files/2015/05/f22/2014%20Hydropower%20Market%20Report_20150512_rev6.pdf |archive-date=1 February 2017 |access-date=19 February 2017 |publisher=U.S. Department of Energy}}</ref>▼
The six largest operational pumped-storage plants are listed below ''(for a detailed list see [[List of pumped-storage hydroelectric power stations]])'':
Line 150 ⟶ 191:
In September 2022, a pumped hydroelectric storage (PHES) scheme was announced at Pioneer-Burdekin in central Queensland that has the potential to be the largest PHES in the world at 5 GW.
China has the largest capacity of pumped-storage hydroelectricity in the world.
In January 2019, the [[State Grid Corporation of China]] announced plans to invest US$5.7 billion in five pumped hydro storage plants with a total 6 GW capacity, to be located in Hebei, Jilin, Zhejiang, Shandong provinces, and in Xinjiang Autonomous Region. China is seeking to build 40 GW of pumped hydro capacity installed by 2020.<ref>{{Cite news |last=Shen |first=Feifei |date=January 9, 2019 |title=China's State Grid to Spend $5.7 Billion on Pumped Hydro Plants |work=Bloomberg.com |url=https://www.bloomberg.com/news/articles/2019-01-09/china-s-state-grid-to-spend-5-7-billion-on-pumped-hydro-plants |url-status=live |access-date=2019-01-18 |archive-url=https://web.archive.org/web/20190119121201/https://www.bloomberg.com/news/articles/2019-01-09/china-s-state-grid-to-spend-5-7-billion-on-pumped-hydro-plants |archive-date=19 January 2019}}</ref>▼
=== Norway ===
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The largest one, Saurdal, which is part of the [[Ulla-Førre]] complex, has four 160 MW [[Francis turbine]]s, but only two are reversible. The lower reservoir is at a higher elevation than the station itself, and thus the water pumped up can only be used once before it has to flow to the next station, Kvilldal, further down the tunnel system. And in addition to the lower reservoir, it will receive water that can be pumped up from 23 river/stream and small reservoir intakes. Some of which will have already gone through a smaller power station on its way.
===United States===
In 2010, the United States had 21.5 GW of pumped storage generating capacity (20.6% of world capacity).<ref>{{Cite web |title=Report: An Updated Annual Energy Outlook 2009 Reference Case Reflecting Provisions of the American Recovery and Reinvestment Act and Recent Changes in the Economic Outlook |url=http://www.eia.doe.gov/oiaf/servicerpt/stimulus/excel/aeostimtab_9.xls |archive-url=https://web.archive.org/web/20100528144341/http://www.eia.doe.gov/oiaf/servicerpt/stimulus/excel/aeostimtab_9.xls |archive-date=2010-05-28 |access-date=2010-10-29}}</ref>
▲
==Hybrid systems==
Conventional hydroelectric dams may also make use of pumped storage in a hybrid system that both generates power from water naturally flowing into the reservoir as well as storing water pumped back to the reservoir from below the dam. The [[Grand Coulee Dam]] in the United States was expanded with a pump-back system in 1973.<ref>{{Cite book |title=Alternative Energy and Shale Gas Encyclopedia |publisher=Wiley |year=2016 |isbn=978-0470894415 |editor-last=Lehr |editor-first=Jay H. |edition=1st |page=424 |editor-last2=Keeley |editor-first2=Jack}}</ref> Existing dams may be repowered with reversing turbines thereby extending the length of time the plant can operate at capacity. Optionally a pump back powerhouse such as the [[Richard B. Russell Dam|Russell Dam]] (1992) may be added to a dam for increased generating capacity. Making use of an existing dam's upper reservoir and transmission system can expedite projects and reduce costs.
▲In January 2019, the [[State Grid Corporation of China]] announced plans to invest US$5.7 billion in five pumped hydro storage plants with a total 6 GW capacity, to be located in Hebei, Jilin, Zhejiang, Shandong provinces, and in Xinjiang Autonomous Region. China is seeking to build 40 GW of pumped hydro capacity installed by 2020.<ref>{{Cite news |last=Shen |first=Feifei |date=January 9, 2019 |title=China's State Grid to Spend $5.7 Billion on Pumped Hydro Plants |work=Bloomberg.com |url=https://www.bloomberg.com/news/articles/2019-01-09/china-s-state-grid-to-spend-5-7-billion-on-pumped-hydro-plants |url-status=live |access-date=2019-01-18 |archive-url=https://web.archive.org/web/20190119121201/https://www.bloomberg.com/news/articles/2019-01-09/china-s-state-grid-to-spend-5-7-billion-on-pumped-hydro-plants |archive-date=19 January 2019}}</ref>
▲== Potential technologies ==
▲===Seawater===
▲Pumped storage plants can operate with seawater, although there are additional challenges compared to using fresh water, such as saltwater corrosion and barnacle growth.<ref>{{cite Q|Q107212803}}</ref> Inaugurated in 1966, the 240 MW [[Rance Tidal Power Station|Rance tidal power station]] in France can partially work as a pumped-storage station. When high tides occur at off-peak hours, the turbines can be used to pump more seawater into the reservoir than the high tide would have naturally brought in. It is the only large-scale power plant of its kind.
▲In 1999, the 30 MW [[Okinawa Yanbaru Seawater Pumped Storage Power Station|Yanbaru project]] in Okinawa was the first demonstration of seawater pumped storage. It has since been decommissioned. A 300 MW seawater-based Lanai Pumped Storage Project was considered for Lanai, Hawaii, and seawater-based projects have been proposed in Ireland.<ref>{{Cite web |date=18 February 2012 |title=Massive Energy Storage, Courtesy of West Ireland |url=https://www.science.org/content/article/massive-energy-storage-courtesy-west-ireland |url-status=live |archive-url=https://web.archive.org/web/20170908034315/http://www.sciencemag.org/news/2012/02/massive-energy-storage-courtesy-west-ireland |archive-date=8 September 2017 |access-date=21 June 2017 |website=sciencemag.org}}</ref> A pair of proposed projects in the [[Atacama Desert]] in northern Chile would use 600 MW of photovoltaic solar (Skies of Tarapacá) together with 300 MW of pumped storage (Mirror of Tarapacá) lifting seawater {{convert|600|m}} up a coastal cliff.<ref>{{Cite web |date=11 March 2015 |title=Project Espejo de Tarapacá |url=http://valhalla.cl/espejo-de-tarapaca/ |url-status=live |archive-url=https://web.archive.org/web/20170618160703/http://valhalla.cl/espejo-de-tarapaca/ |archive-date=18 June 2017 |access-date=19 June 2017 |website=Valhalla}}</ref><ref>{{Cite web |date=4 May 2016 |title=The Mirror of Tarapaca: Chilean power project harnesses both sun and sea |url=https://www.power-technology.com/features/featurethe-mirror-of-tarapaca-chilean-power-project-harnesses-both-sun-and-sea-4872272/ |url-status=live |archive-url=https://web.archive.org/web/20190504012539/https://www.power-technology.com/features/featurethe-mirror-of-tarapaca-chilean-power-project-harnesses-both-sun-and-sea-4872272/ |archive-date=4 May 2019 |access-date=4 May 2019}}</ref>
▲===Freshwater coastal reservoirs===
▲Freshwater from the river floods is stored in the sea area replacing seawater by constructing [[coastal reservoir]]s. The stored river water is pumped to uplands by constructing a series of embankment canals and pumped storage hydroelectric stations for the purpose of energy storage, irrigation, industrial, municipal, rejuvenation of exploited rivers, etc. These multipurpose coastal reservoir projects offer massive pumped-storage hydroelectric potential to utilize variable and intermittent solar and wind power that are carbon-neutral, clean, and renewable energy sources.<ref>{{Cite journal |last=Sasidhar |first=Nallapaneni |date=May 2023 |title=Multipurpose Freshwater Coastal Reservoirs and Their Role in Mitigating Climate Change |url=https://www.ijee.latticescipub.com/wp-content/uploads/papers/v3i1/A1842053123.pdf |access-date=2023-05-23 |journal=Indian Journal of Environment Engineering |issn=2582-9289 |volume=3 |issue=1|pages=30–45 |doi=10.54105/ijee.A1842.053123 |s2cid=258753397 }}</ref>
▲===Underground reservoirs===
▲The use of underground reservoirs has been investigated.<ref>{{Cite book |last=Pummer |first=Elena |url=http://publications.rwth-aachen.de/record/667419/files/667419.pdf |title=Hybrid Modelling of the Hydrodynamic Processes in Underground Pumped Storage Plants |publisher=RWTH Aachen University |year=2016 |location=Aachen, Germany |access-date=19 May 2020 |archive-url=https://web.archive.org/web/20201104044602/http://publications.rwth-aachen.de/record/667419/files/667419.pdf |archive-date=4 November 2020 |url-status=live}}</ref> Recent examples include the proposed Summit project in [[Norton, Ohio]], the proposed Maysville project in [[Kentucky]] (underground limestone mine), and the Mount Hope project in [[New Jersey]], which was to have used a former iron mine as the lower reservoir. The proposed energy storage at the [[Callio]] site in [[Pyhäjärvi]] ([[Finland]]) would utilize the deepest base metal mine in Europe, with {{Convert|1450|m|ft}} elevation difference.<ref>{{Cite news |title=Energy storage |language=en-US |work=Callio Pyhäjärvi |url=https://callio.info/energy-storage/opportunities/ |url-status=live |access-date=2018-03-14 |archive-url=https://web.archive.org/web/20180315050701/https://callio.info/energy-storage/opportunities/ |archive-date=15 March 2018}}</ref> Several new underground pumped storage projects have been proposed. Cost-per-kilowatt estimates for these projects can be lower than for surface projects if they use existing underground mine space. There are limited opportunities involving suitable underground space, but the number of underground pumped storage opportunities may increase if abandoned coal mines prove suitable.<ref>{{Cite web |date=17 March 2017 |title=German Coal Mine to Be Reborn as Giant Pumped Storage Hydro Facility |url=http://www.renewableenergyworld.com/articles/2017/03/german-coal-mine-to-be-reborn-as-giant-pumped-storage-hydro-facility.html |url-status=live |archive-url=https://web.archive.org/web/20190709081435/https://www.renewableenergyworld.com/articles/2017/03/german-coal-mine-to-be-reborn-as-giant-pumped-storage-hydro-facility.html |archive-date=9 July 2019 |access-date=20 March 2017}}</ref>
▲In [[Bendigo]], Victoria, Australia, the Bendigo Sustainability Group has proposed the use of the old gold mines under Bendigo for Pumped Hydro Energy Storage.<ref>{{Cite web |last=Smith |first=Trevor |title=Bendigo Mines Pumped Hydro Project |url=https://www.bsg.org.au/bendigo-pumped-hydro-project/ |url-status=live |archive-url=https://web.archive.org/web/20180715235943/https://www.bsg.org.au/bendigo-pumped-hydro-project/ |archive-date=15 July 2018 |access-date=2020-07-13 |website=Bendigo Sustainability Group |language=en-AU}}</ref> Bendigo has the greatest concentration of deep shaft hard rock mines anywhere in the world with over 5,000 shafts sunk under Bendigo in the second half of the 19th Century. The deepest shaft extends 1,406 metres vertically underground. A recent pre-feasibility study has shown the concept to be viable with a generation capacity of 30 MW and a run time of 6 hours using a water head of over 750 metres.
▲US-based start-up Quidnet Energy is exploring using abandoned oil and gas wells for pumped storage. If successful they hope to scale up, utilizing some of the 3 million abandoned wells in the US.<ref>{{Cite news |last=Lo |first=Chris |date=27 November 2016 |title=Could depleted oil wells be the next step in energy storage? |url=https://www.power-technology.com/analysis/featurecould-depleted-oil-wells-be-the-next-step-in-energy-storage-5680002/ |access-date=16 May 2022}}</ref><ref>{{Cite web |title=Press Release: CPS Energy & Quidnet Energy Announce Landmark Agreement to Build Grid-Scale, Long Duration, Geomechanical Pumped Storage Project in Texas |url=https://www.quidnetenergy.com/news/2022/03/cps-energy--quidnet-energy-announce-landmark-agreement-to-build-gridscale-long-duration-geomechanical-pumped-storage-project-in-texas/ |access-date=16 May 2022 |website=quidnetenergy.com}}</ref>
▲===Decentralised systems===
▲Small (or micro) applications for pumped storage could be built on streams and within infrastructures, such as drinking water networks<ref>{{Cite web |title=Senator Wash |url=http://www.iid.com/water/water-transportation-system/colorado-river-facilities/senator-wash |url-status=live |archive-url=https://web.archive.org/web/20160626043856/http://www.iid.com/water/water-transportation-system/colorado-river-facilities/senator-wash |archive-date=26 June 2016 |access-date=6 August 2016 |website=www.iid.com |publisher=Imperial Irrigation District |language=en}}</ref> and artificial snow-making infrastructures. In this regard, a storm-water basin has been concretely implemented as a cost-effective solution for a water reservoir in a micro-pumped hydro energy storage.<ref name=":1a" /> Such plants provide distributed [[energy storage]] and distributed flexible [[electricity production]] and can contribute to the decentralized integration of [[intermittent renewable energy]] technologies, such as [[wind power]] and [[solar power]]. Reservoirs that can be used for small pumped-storage hydropower plants could include<ref name="Thesis">{{Cite book |last=Crettenand |first=N. |url=https://infoscience.epfl.ch/record/176337?ln=en |title=The facilitation of mini and small hydropower in Switzerland: shaping the institutional framework. With a particular focus on storage and pumped-storage schemes |publisher=Ecole Polytechnique Fédérale de Lausanne |year=2012 |archive-url=https://web.archive.org/web/20180913040049/https://infoscience.epfl.ch/record/176337?ln=en |archive-date=13 September 2018 |type=PhD Thesis N° 5356.}}</ref> natural or artificial lakes, reservoirs within other structures such as irrigation, or unused portions of mines or underground military installations. In [[Switzerland]] one study suggested that the total installed capacity of small pumped-storage hydropower plants in 2011 could be increased by 3 to 9 times by providing adequate [[Market-based environmental policy instruments|policy instruments]].<ref name="Thesis" />
▲===Underwater reservoirs===
▲{{Further|Stored Energy at Sea}}
▲In March 2017, the research project StEnSea (Storing Energy at Sea) announced their successful completion of a four-week test of a pumped storage underwater reservoir. In this configuration, a hollow sphere submerged and anchored at great depth acts as the lower reservoir, while the upper reservoir is the enclosing body of water. Electricity is created when water is let in via a reversible turbine integrated into the sphere. During off-peak hours, the turbine changes direction and pumps the water out again, using "surplus" electricity from the grid.
▲The quantity of power created when water is let in, grows proportionally to the height of the column of water above the sphere. In other words: the deeper the sphere is located, the more densely it can store energy.
▲As such, the energy storage capacity of the submerged reservoir is not governed by the [[gravitational energy]] in the traditional sense, but by the [[vertical pressure variation]].
▲===Home use===
▲Using a pumped-storage system of [[cistern]]s and small generators, [[pico hydro]] may also be effective for "closed loop" home energy generation systems.<ref name="sciencedaily">{{Cite web |date=2016-10-24 |title=Is energy storage via pumped hydro systems is possible on a very small scale? |url=https://www.sciencedaily.com/releases/2016/10/161024090454.htm |archive-url=https://web.archive.org/web/20170510054924/https://www.sciencedaily.com/releases/2016/10/161024090454.htm |archive-date=2017-05-10 |access-date=6 September 2018 |website=Science Daily}}</ref><ref name="homepower">{{Cite news |last=Root |first=Ben |date=December 2011 – January 2012 |title=Microhydro Myths & Misconceptions |volume=146 |page=77 |publisher=Home Power |url=https://www.homepower.com/articles/microhydro-power/design-installation/microhydro-myths-misconceptions |access-date=6 September 2018 |archive-url=https://web.archive.org/web/20180905214822/https://www.homepower.com/articles/microhydro-power/design-installation/microhydro-myths-misconceptions |archive-date=5 September 2018}}</ref>
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▲===Hydraulic Fracturing===
▲Using [[hydraulic fracturing]] pressure can be stored underground in [[Permeability_(Earth_sciences)|impermeable]] strata such as shale.<ref>{{cite journal|title= Is Hydraulic Fracturing the Next Big Breakthrough in Battery Tech?|journal= [[Society_of_Petroleum_Engineers#Magazines|Journal of Petroleum Technology]]|publisher= [[Society of Petroleum Engineers]]|volume= 75|number =10|date =October 2023|pages= 36–41|last= Jacobs|first= Trent}}</ref> The shale used contains no hydrocarbons.<ref name="TM91221">{{Cite news |last=Russell Gold |date=September 21, 2021 |title=Fracking Has a Bad Rep, but Its Tech Is Powering a Clean Energy Shift Texas start-ups are harnessing know-how born of the shale boom in pursuit of a greener future. |work=Texas Monthly |url=https://www.texasmonthly.com/news-politics/fracking-clean-energy-geothermal/ |url-status=live |access-date=September 23, 2021 |archive-url=https://web.archive.org/web/20210924171206/https://www.texasmonthly.com/news-politics/fracking-clean-energy-geothermal/ |archive-date=24 September 2021}}</ref>
▲===Electrolysis===
▲One idea to reduce pumping energy requirements is to use [[electrolysis of water|electricity to split water]] at a low elevation, and then pipe the lighter-than-air hydrogen to a high elevation where it could be burned with atmospheric oxygen to produce water. This high-elevation water could then be returned to the low elevation, potentially more than recovering efficiency losses by harvesting the gravitational potential energy of higher-altitude atmospheric oxygen (which is later harmlessly re-mixed by sun-powered wind).<ref>{{cite news |title=Recharging the power grid |page=13 |date=May 2003 |magazine=Technology Review |author=Charles I. Clausing}}</ref>
▲===High-density pumped hydro===
▲RheEnergise<ref name="RheEnergise">[https://www.rheenergise.com/ RheEnergise company website]</ref> aim to improve the efficiency of pumped storage by using fluid 2.5x denser than water ("a fine-milled suspended solid in water"<ref name="IoME article">[https://www.imeche.org/news/news-article/high-density-pumped-hydro-could-be-installed-on-thousands-of-small-hills]Institution of Mechanical Engineers article</ref>), such that "projects can be 2.5x smaller for the same power."<ref name="RheEnergise_how_it_works">[https://www.rheenergise.com/how-it-works] RheEnergise 'how it works' article</ref>
== See also ==
Line 211 ⟶ 217:
== References ==
{{Reflist
== External links ==
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