Pumped-storage hydroelectricity

A diagram of the TVA pumped storage facility at Raccoon Mountain Pumped-Storage Plant in Tennessee, United States

A shaded-relief topo map of the Taum Sauk pumped storage plant in Missouri, United States. The lake on the mountain is built upon a flat surface, requiring a dam around the entire perimeter.

Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method 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 turbines to produce electric power.

Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar, 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.^[1]^[2] 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 generally varies between 70%–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, PSH accounts for around 95% of all active storage installations worldwide, with a total installed throughput capacity of over 181 GW and a total installed storage capacity of over 1.6 TWh.^[3]

^ "Storage for a secure Power Supply from Wind and Sun" (PDF). Archived (PDF) from the original on 23 February 2011. Retrieved 21 January 2011.
^ Rehman, Shafiqur; Al-Hadhrami, Luai; Alam, Md (30 April 2015). "Pumped hydro energy storage system: A technological review". Renewable and Sustainable Energy Reviews. 44: 586–598. doi:10.1016/j.rser.2014.12.040. Archived from the original on 8 February 2022. Retrieved 15 November 2016 – via ResearchGate.
^ "DOE OE Global Energy Storage Database". U.S. Department of Energy Energy Storage Systems Program. Sandia National Laboratories. 8 July 2020. Archived from the original on 9 July 2021. Retrieved 12 July 2020.

[1] "Storage for a secure Power Supply from Wind and Sun" (PDF). Archived (PDF) from the original on 23 February 2011. Retrieved 21 January 2011.

[2] Rehman, Shafiqur; Al-Hadhrami, Luai; Alam, Md (30 April 2015). "Pumped hydro energy storage system: A technological review". Renewable and Sustainable Energy Reviews. 44: 586–598. doi:10.1016/j.rser.2014.12.040. Archived from the original on 8 February 2022. Retrieved 15 November 2016 – via ResearchGate.

[3] "DOE OE Global Energy Storage Database". U.S. Department of Energy Energy Storage Systems Program. Sandia National Laboratories. 8 July 2020. Archived from the original on 9 July 2021. Retrieved 12 July 2020.

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