Pumped Hydro – The Big Battery Solution

This century-old technology could be the key to unlocking America’s renewable energy future; Pumped storage hydro once propped up coal and nuclear power. Now it's essential for a clean, growing grid.

James Dinneen April 14, 2021 (Popular Science)

“…To guarantee a smooth, carbon-free supply of electricity despite [wind and solar] variability, the grid requires enormous amounts of energy storage, and projections indicate that the region needs up to 10,000 megawatts of backup reserves to meet 100-percent renewable power goals…[Pumped hydro storage] could help make up some of that looming storage deficit…[P]umped storage hydro taps surplus energy from the grid to push water from a lower reservoir up to a higher one. When utilities need the power back, flows are released through a hydroelectric turbine, generating electricity.

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Some designs use a natural water body for one or both of the reservoirs (called “open loop”), while others circulate water between a pair of standalone reservoirs (called “closed loop”)…Existing pumped storage hydro accounts for about 95 percent of America’s 23,200 megawatts of energy storage capacity. But as power consumption and blackouts escalate, more such projects, big and small, will be needed…Lithium-ion batteries coming online all around the country rarely supply more than 100 megawatts of electricity for more than four hours…Pumped storage hydro systems are only limited by the size of the reservoir…. [A coalition of hydroelectric energy companies and environmentalists agree on] closed-loop designs and the possibility of retrofitting existing dams…[There also may be] interest in smaller (think less than a gigawatt) projects…

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…[Presently, pumped hydro competes] with increasingly cheap lithium-ion battery storage, which can be installed anywhere and provides the kind of short-duration backup the market currently values…[But] at a certain level of renewable penetration—around 80 percent, depending on the mix of sources—the short-duration storage provided by batteries will be inadequate to support the grid…” click here for more

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