What is a pumped storage power station?
A pumped storage power station is a hydroelectric plant that stores electricity by moving water between an upper reservoir and a lower reservoir or river. When power is cheap and plentiful, for example at night or when wind and solar output is high, it pumps water uphill. When demand rises, the water flows back down through turbines and generates electricity again. In Dutch it is called a spaarbekkencentrale or pompcentrale.
Layout and operation
- Upper reservoir: a natural lake or artificial basin with a large storage volume.
- Lower reservoir or river: receives the water after it has passed the turbines.
- Pump-turbines: often reversible machines that can both pump and generate.
- Spillway: discharges excess water safely.
Output depends on head and flow: P = ρ · g · Q · H · η. The greater the head, the more energy each cubic metre of water carries. Typically 70-80% of the electricity put in is recovered; the US EIA reported an average round-trip efficiency of 79% for 2019.
Application
- Grid balancing. Pumped storage can ramp up or shut down within minutes, smoothing out fluctuations from wind and solar power.
- Location. A substantial height difference is needed, so plants are built in hilly or mountainous terrain. Britain’s largest is Dinorwig in North Wales, with 1,728 MW and around 9.1 GWh of storage.
- Storage versus attenuation. A storage reservoir keeps water for later use; an attenuation or retention basin only holds water temporarily to prevent flooding.
Common mistake: treating pumped storage as an extra source of energy. It is a net consumer of electricity; its value lies in shifting power from times of surplus to times of shortage.
Related terms
- Power plant
- Energy storage
- Green electricity
- Tidal power station
- Wave power plant
- Storage basin
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