"For a century, hydroelectric power has been synonymous with gigantic dams — feats of engineering that provide renewable energy but displace communities and destroy ecosystems.

New research released Tuesday by Global Energy Monitor reveals a transformation underway in hydroelectric projects — using the same gravitational qualities of water, but typically without building large, traditional dams like the Hoover in the American West or Three Gorges in China. Instead, a technology called pumped storage is rapidly expanding.

These systems involve two reservoirs: one on top of a hill and another at the bottom. When electricity generated from nearby power plants exceeds demand, it’s used to pump water uphill, essentially filling the upper reservoir as a battery. Later, when electricity demand spikes, water is released to the lower reservoir through a turbine, generating power.

Pumped storage isn’t a new idea. But it is undergoing a renaissance in countries where wind and solar power are also growing, helping allay concerns about weather-related dips in renewable energy output."

Mira Rojanasakul and Max Bearak report for the New York Times May 2, 2023. [2]