Pumped Hydro Energy Storage Is Having a Renaissance

The article highlights a renewed interest and innovation in pumped hydro energy storage as the world integrates more renewable energy sources into power grids. Pumped hydro, a technology dating back centuries, stores energy by moving water between reservoirs at different elevations to generate electricity when needed. Traditionally reliant on large reservoirs and high elevations, the technology is now being reimagined to better suit modern grid demands, particularly to balance the variability of wind and solar power. A key example is RheEnergise, a British company developing a novel system using a mineral-based fluid denser than water, allowing energy storage in smaller spaces and at lower elevations. Their demonstration plant near Plymouth, England, uses this fluid to drive turbines and store energy more efficiently, potentially unlocking thousands of new viable sites for pumped hydro globally. This renaissance in pumped hydro is driven by the urgent need to reduce wasted renewable energy—such as the UK's £1 billion loss from curtailed wind power in 2024—and to provide flexible, rapid-response grid balancing. The