Environmental and geographic constraints shape global pumped hydro for long-duration storage

Abstract

Long-duration energy storage is essential for stabilizing electricity systems dominated by wind and solar power, with pumped hydroelectric storage (PHS) as a mature long-duration storage solution. Yet the global potential of PHS under realistic hydrological, environmental, and social constraints has not been systematically quantified. Here we present a global bottom-up assessment integrating hydrology, topography, environment, and transmission accessibility. Screening 2.89 million river and 50 million mountain valleys, we identify 18.82 ± 2.66 PWh of economically and environmentally viable PHS resources that are highly concentrated in mountainous regions. Even under projected cost reductions of competing storage technologies through 2050, PHS remains the most cost-effective option for storage durations exceeding four hours and could deliver over 100 hours of storage for over half of global electricity demand. This study defines a physically constrained benchmark for the role of PHS in future power systems and provides a framework for integrating complementary storage technologies to support resilient, low-carbon electricity systems.