The Renaissance of Pumped Hydro Energy Storage

Pumped hydro energy storage (PHES) has its origins in the late 19th century, with significant development occurring throughout the 20th century, particularly in the United States and the United Kingdom. Initially designed to complement fossil fuel power plants by utilizing excess energy, the construction of pumped hydro facilities declined by the 1990s. However, the increasing integration of renewable energy sources, such as wind and solar, has renewed interest in pumped hydro as a flexible solution for managing energy supply and demand.

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Today, grid operators face challenges related to energy waste, as evidenced by the UK losing over £1 billion ($1.32 billion) in 2023 due to the shutdown of wind turbines when demand was low. Pumped hydro plants offer a solution by quickly balancing shortfalls in electricity generation and absorbing surplus energy. RheEnergise, a company innovating in this space, has developed a denser-than-water fluid that allows for more compact energy storage solutions. This advancement could enable the establishment of pumped hydro facilities in locations previously deemed unsuitable due to geographical constraints.

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RheEnergise claims that while traditional pumped hydro sites in the UK are limited to approximately 20-25 viable locations, their technology could identify around 6,500 potential sites. This opens the door for hundreds of thousands of locations worldwide, contingent upon successful testing and implementation. The company recently reported generating its first power from a 500 kilowatt (kW) demonstrator, with plans for a commercial-scale 10 megawatt (MW) project by 2028 if results remain promising.

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The International Hydropower Association (IHA) highlights the growing significance of pumped hydro, estimating that 600 gigawatts (GW) of projects are currently in the global pipeline, with 8.4 GW installed in 2024 alone. A notable contributor to this growth is the 3.6 GW pumped hydro plant in Fengning, China, recognized as the largest facility in the world by power capacity.

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Rebecca Ellis, senior energy policy manager at the IHA, remarked on the exciting developments in pumped hydro technology, emphasizing its potential to address energy storage challenges effectively. RheEnergise's innovations could play a crucial role in reshaping energy storage solutions, particularly in regions with limited traditional pumped hydro options.

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Despite the optimism surrounding pumped hydro, critics point to the historical challenges of high construction costs and the complexity of building such facilities. Skeptics question whether the advancements made by companies like RheEnergise can overcome these barriers and achieve widespread adoption.

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While the IHA reports significant growth in pumped hydro installations, the exact number of operational facilities and their capacities can vary between sources. There is also uncertainty regarding the feasibility of RheEnergise's technology in diverse geographical contexts, which remains to be validated through ongoing testing.

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“It’s a really exciting time,” — Rebecca Ellis, Senior Energy Policy Manager, International Hydropower Association

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“In somewhere like the UK, we think there are probably 20–25 viable sites for traditional pumped hydro, whereas for us it’s 6,500,” — Crosher, RheEnergise

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