Pumpedstorage

Pumped-storage, or pumped-storage hydroelectric power, is a method of storing energy by moving water between two reservoirs at different elevations. During periods of low electricity demand, surplus power is used to pump water from a lower to an upper reservoir. When demand rises, water is released back through turbines to generate electricity, providing grid-scale storage and rapid response.

A typical facility comprises an upper reservoir, a lower reservoir, and a system of tunnels or penstocks connecting them, with reversible turbines that can operate as both pumps and generators. The energy stored depends on the height difference (the head) and the volume of water; pumped-storage plants can be built in mountain regions or valleys with suitable geography.

Efficiency in pumped storage is usually in the range of 70 to 85 percent for the full cycle, varying with turbine technology and operating conditions. The plants offer high ramp rates and long service lives, making them well suited for balancing variable renewable generation and providing peak power and grid reliability.

Development considerations include high upfront costs, long construction times, environmental and land-use impacts, and water resource management. Despite these factors, pumped-storage remains a dominant form of large-scale energy storage worldwide due to its maturity, scalability, and ability to provide sustained energy during multi-hour demand peaks.