Pumped Hydro Energy Storage Is Having a Renaissance

The Resurgence of Pumped Hydro Energy Storage

In a quiet corner of Devon, England, workers began adding a secret, light brown powder to water as they mixed up a special fluid that can store energy. This fluid, 2.5 times denser than water, is the brainchild of RheEnergise, a British energy-storage company. The goal was to achieve a mixture that flows easily, like a giant protein shake, over the course of multiple weeks. This denser-than-water fluid means the firm can pack more potential energy into a smaller space and at lower elevations.

Pumped hydro first emerged in the late 19th century, with countries like the US and UK building large plants to complement fossil fuel power plants. However, construction had waned by the 1990s. Today, grid operators increasingly value pumped hydro plants as workhorses able to mediate highly variable wind and solar assets. They can fill in shortfalls in electricity generation or soak up surplus energy within minutes, and store it for short or long periods.

The Challenge of Energy Storage

Currently, significant amounts of energy go to waste because there's no way to consume it at the moment of generation. The UK, for one, has squandered more than £1 billion ($1.32 billion) this year alone by turning off wind turbines due to lack of energy demand. Pumped hydro plants could help to solve this problem but building them has often been expensive and difficult.

RheEnergise's Innovative Approach

RheEnergise's denser-than-water fluid means the firm can pack more potential energy into a smaller space and at lower elevations. To replicate the firm's 500 kilowatt (kW) demonstrator with a water-based version, for example, you'd need more than twice the volume of liquid they're using, and the upper reservoir would need to be elevated to 200 meters rather than 80. This could open up new possibilities for pumped hydro projects in areas with limited geographical constraints.

The Global Potential of Pumped Hydro

The International Hydropower Association (IHA) estimates that 600 GW of pumped hydro projects are in the global pipeline. 8.4 GW was installed in 2024, with one project that helped boost that total being the 3.6 GW pumped hydro plant in Fengning, China. It's the biggest such facility, in terms of power capacity, in the world.

The Benefits of Pumped Hydro

Day in, day out, plants like this move water up hills and down hills on a gigantic scale—and with incredible power. Goldisthal in central Germany is a prime example, with an upper reservoir containing approximately 12 million cubic meters of water—enough to fill 4,800 Olympic swimming pools—is linked by a pumped hydro power station to a lower reservoir of nearly 19 million cubic meters. It has two 800-meter-long penstocks, slanting tubes connecting the reservoirs, and, at maximum power, a capacity of 1.06 GW.

The Challenges of Large-Scale Pumped Hydro

In Australia, a truly massive pumped hydro project called Snowy 2.0 is currently under construction. It is an expansion of an existing pumped hydro system that utilizes lakes in the Snowy Mountains of southern Australia. While Goldisthal can provide a total of 8.5 gigawatt hours (GWh) of energy—its 1.06 GW capacity delivered over a maximum of 8.5 hours—Snowy 2.0 will offer an astonishing 350 GWh when completed. However, Snowy 2.0 has been beset by delays and cost overruns.

The Future of Pumped Hydro

If you want serious storage, you want pumped hydro, says Andrew Blakers of Australian National University. The UK, for one, is currently "not serious" about pumped hydro and won't be until it constructs a 500 GWh system at Loch Ness in Scotland. Multiple firms are vying to install new pumped hydro infrastructure there, though these schemes have faced local opposition.

Conclusion

Pumped hydro energy storage is having a renaissance, with innovative approaches like RheEnergise's denser-than-water fluid opening up new possibilities for the technology. While large-scale, traditional pumped hydro has its place, the world needs climate solutions fast. The global potential of pumped hydro is vast, with 600 GW of projects in the pipeline. However, the challenges of large-scale pumped hydro, such as delays and cost overruns, must be addressed. As the world continues to transition to renewable energy, pumped hydro will play an increasingly important role in mediating variable wind and solar assets.

Source: https://www.wired.com/story/pumped-hydro-energy-storage-is-having-a-renaissance/