Pumped-storage_hydroelectricity

# Pumped-storage hydroelectricity **Pumped-storage hydroelectricity** stores electrical [[Energy|energy]] by pumping [[Water|water]] from a lower reservoir to an upper one when power is plentiful and releasing it through turbines when demand is high; the same reversible machines serve as pumps and as generators.[^kerlin-9] The energy stored is E = ρgVH, so a high head needs less water, and every cycle loses a share to the pumps and the turbines. It is by far the largest form of [[Grid_energy_storage|grid energy storage]]: world pumped-storage capacity reached 189 GW at the end of 2024.[^iha2025] In the Thury spine it is [[Hydroelectricity|hydroelectricity]] run in both directions — water lifted instead of fallen. <div class="microsim-player"> <iframe src="https://wikitube-3d-microsims.netlify.app/Pumped-storage_hydroelectricity.html" width="100%" height="620" frameborder="0" loading="lazy" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Pumped-storage hydroelectricity — p5.js microsim"></iframe> </div> *Microsim (THY-066): run a day at a plant sized like TVA's Raccoon Mountain; pump at night, generate at the evening peak, and change the head and machine efficiency. ILLUSTRATIVE: a smooth two-peak demand curve and fixed pumping and generating hours.* Videos: [16:9](https://wikitube-3d-microsims.netlify.app/media/Pumped-storage_hydroelectricity_16x9.mp4) · [9:16](https://wikitube-3d-microsims.netlify.app/media/Pumped-storage_hydroelectricity_9x16.mp4) ## Basic principle Pumps powered by plants that would otherwise be idle at night lift water to an elevated reservoir; when demand is high the water is released through turbine-generators at the lower elevation, the machines running in reverse.[^kerlin-9] The plant is a net consumer of energy — pumping and generating each lose some — but it moves energy from hours when it is worth little to hours when it is worth much. The Raccoon Mountain station of the Tennessee Valley Authority, near Chattanooga, uses a 230-foot dam on the mountaintop to form a 528-acre upper reservoir; water falls 990 feet to generate more than 1,500 MW.[^kerlin-9] ## Types Closed-loop plants cycle the same water between two reservoirs isolated from natural rivers; open-loop plants use a reservoir on a river as one of the pair. A few plants add pumping to a conventional hydroelectric dam. ## Economic efficiency The round-trip efficiency is the product of the pumping and generating efficiencies; with machines around 90% each, about 80% of the energy used for pumping comes back. The economics rest on the price difference between the hours of pumping and of generating, and on the value of fast, flexible capacity to the grid. Pumping suits power plants with low operating costs that can run at night — wind turbines, geothermal and nuclear plants — rather than fossil plants, whose fuel dominates their costs, or solar plants, which are idle at night.[^kerlin-9] ### Small-scale facilities Small pumped-storage schemes are possible, but losses and costs weigh more heavily at small scale, and batteries compete strongly for short-duration storage. ## Location requirements A good site needs two bodies of water close together with a large difference in height, suitable geology for tunnels and reservoirs, and access to transmission. Such sites are few, which limits how much pumped storage can be built.[^murphy-16] ## Environmental impact Building reservoirs floods land and can affect streams and wildlife; closed-loop plants, which do not dam a flowing river, generally have smaller effects on fisheries than open-loop plants. ## Potential technologies Proposals extend pumped storage beyond mountain valleys: seawater as the lower reservoir, underground caverns or old mines as one reservoir, and dense fluids in place of water to raise the energy stored per metre of head. ## History Utilities built pumped storage to pair with plants that run most cheaply at steady output, storing their night-time energy for the daytime peak; the Tennessee Valley Authority's Raccoon Mountain station is a large example.[^kerlin-9] ## Worldwide use In 2024 the world added 8.4 GW of pumped-storage capacity, a 5% increase to 189 GW, and the development pipeline included about 600 GW of pumped storage.[^iha2025] ### United States Raccoon Mountain, operated by the Tennessee Valley Authority, is one of the large U.S. facilities, with a 990-foot drop and more than 1,500 MW of capacity.[^kerlin-9] ## Hybrid systems Pumped storage can be combined with wind or solar farms so that their surplus output is stored as water; a conventional reservoir paired with wind does something similar without pumping, by holding water back while the wind blows. The Manitoba–Minnesota interconnection, energized in June 2020, lets Manitoba's hydroelectric stations back up Minnesota Power's wind generation.[^mb-hydro] ## See also - [[Grid_energy_storage]] - [[Hydroelectricity]] - [[Francis_turbine]] - [[Capacity_factor]] ## References [^kerlin-9]: Kerlin, Thomas W. (2013). *Future Energy: Opportunities & Challenges*, ch. 9 "Hydroenergy," pp. 203–216 (§9.4 dams and small systems; §9.5 pumped storage; §9.6 river-flow converters). ISA; CC BY 4.0. https://open.umn.edu/opentextbooks/textbooks/future-energy-opportunities-challenges [^iha2025]: International Hydropower Association (June 25, 2025). "Global hydropower generation rebounds in 2024 and pumped storage development surges — flagship 2025 World Hydropower Outlook out now." https://www.hydropower.org/news/flagship-2025-world-hydropower-outlook-out-now [^murphy-16]: Murphy, Tom W., Jr. (2021). *Energy and Human Ambitions on a Finite Planet*, ch. 16 (hydrogen and battery round-trip efficiency; pumped storage limited by suitable sites). eScholarship, University of California. https://escholarship.org/uc/item/9js5291m [^mb-hydro]: Manitoba Hydro (July 2020). "New transmission line makes grid more reliable and benefits Manitobans." Company release. https://www.hydro.mb.ca/articles/2020/07/new_transmission_line_makes_grid_more_reliable_and_benefits_manitobans/ ### Portal Books - Kerlin, Thomas W. (2013). *Future Energy: Opportunities & Challenges* — [OTL record](https://open.umn.edu/opentextbooks/textbooks/future-energy-opportunities-challenges); on the [[PORTAL_Thury_Hydrodynamics_Apex_Spine]] and [[PORTAL_Energy]] shelves. - Murphy, Tom W., Jr. (2021). *Energy and Human Ambitions on a Finite Planet* — [eScholarship](https://escholarship.org/uc/item/9js5291m); on the [[PORTAL_Energy]] shelf. ## External links - [Types of Hydropower Plants](https://www.energy.gov/eere/water/types-hydropower-plants), U.S. Department of Energy  *Linked from the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]], section 16, Hydroelectricity.*   *Connected to the Apex Spine:* Pumped-storage hydroelectricity → [[Hydropower|Hydropower]] — [[WT!Thury_Hydrodynamics_Compendium|Compendium]] section 15, *Hydropower*.   **Microsim — three.js (Wikitube framework):** *Pumped-storage hydroelectricity* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/thury/Pumped-storage_hydroelectricity.html" data-title="Pumped-storage hydroelectricity"></div> *Built from `MICROSIM_GUIDE/specs/variants/Pumped-storage_hydroelectricity.json`; part of the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]] set.*  ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity) : [Wikitube](https://en.wikitube.io/wiki/Pumped-storage_hydroelectricity) · pinned revision [1367350925](https://en.wikipedia.org/w/index.php?oldid=1367350925) · 2026-09-10 ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_Energy]]. --- *Thury station wave · 2026-09-10 · drafted · microsim THY-066 (p5.js) · parent [[Hydroelectricity]].*