Editing Pumped-storage hydroelectricity (section)

{{Short description|Electric energy storage system}}
{{Redirect|Hydro-storage|storage of water for other purposes|Reservoir}}
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[[File:LudingtonPumpedHydro.png|thumb|[[Ludington Pumped Storage Power Plant]] in [[Michigan]] on [[Lake Michigan]]]]

'''Pumped-storage hydroelectricity''' ('''PSH'''), or '''pumped hydroelectric energy storage''' ('''PHES'''), is a type of [[hydroelectric]] [[energy storage]] used by [[electric power system]]s for [[load balancing (electrical power)|load balancing]]. 
A PSH system stores energy in the form of [[gravitational potential energy]] of water, pumped from a lower elevation [[reservoir]] to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through [[water turbine|turbine]]s to produce electric power.

Pumped-storage hydroelectricity allows energy from [[Intermittent energy source|intermittent sources]] (such as [[solar power|solar]], [[Wind power|wind]], and other renewables) or excess electricity from continuous base-load sources (such as coal or nuclear) to be saved for periods of higher demand.<ref>{{Cite web |title=Storage for a secure Power Supply from Wind and Sun |url=http://poppware.de/Storage_for_a_secure_Power_Supply_from_Wind_and_Sun.pdf |url-status=live |archive-url=https://web.archive.org/web/20110223053809/http://poppware.de/Storage_for_a_secure_Power_Supply_from_Wind_and_Sun.pdf |archive-date=23 February 2011 |access-date=21 January 2011}}</ref><ref>{{Cite journal |last1=Rehman |first1=Shafiqur |url=https://www.researchgate.net/publication/271539381 |title=Pumped hydro energy storage system: A technological review |last2=Al-Hadhrami |first2=Luai |last3=Alam |first3=Md |date=30 April 2015 |journal=Renewable and Sustainable Energy Reviews |volume=44 |pages=586–598 |doi=10.1016/j.rser.2014.12.040 |bibcode=2015RSERv..44..586R |access-date=15 November 2016 |archive-url=https://web.archive.org/web/20220208023518/https://www.researchgate.net/publication/271539381_Pumped_hydro_energy_storage_system_A_technological_review |archive-date=8 February 2022 |url-status=live |via=ResearchGate}}</ref>
The reservoirs used with pumped storage can be quite small, when contrasted with the lakes of conventional hydroelectric plants of similar power capacity, and generating periods are often less than half a day.

The [[round-trip efficiency]] of PSH varies between 70% and 80%. Although the losses of the pumping process make the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of [[peak demand]], when electricity prices are highest. If the upper lake collects significant rainfall, or is fed by a river, then the plant may be a net energy producer in the manner of a traditional hydroelectric plant.

Pumped storage is by far the largest-capacity form of [[grid energy storage]] available, and, {{as of|2020|lc=yes}}, accounts for around 95% of all active storage installations worldwide, with a total installed throughput capacity of over 181 [[Gigawatt|GW]] and as of 2020 a total installed storage capacity of over 1.6 [[TWh]].<ref>{{Cite web |date=8 July 2020 |title=DOE OE Global Energy Storage Database |url=https://www.sandia.gov/ess-ssl/global-energy-storage-database-home/ |url-status=live |archive-url=https://web.archive.org/web/20210709184735/https://www.sandia.gov/ess-ssl/global-energy-storage-database-home/ |archive-date=9 July 2021 |access-date=12 July 2020 |website=U.S. Department of Energy Energy Storage Systems Program |publisher=[[Sandia National Laboratories]]}}</ref>