High-density hydro storage system reaches full power milestone
Pamela Largue
Posted on: 30 January 2026
“The future of long-life, low-cost energy storage is in the hills of Devon,” says Stephen Crosher, Chief Executive of RheEnergise.
RheEnergise has announced that its first-ever High-Density Hydro energy project on the outskirts of Plymouth, UK, is now consistently producing full power at the predicted output.
The milestone, says the UK-headquartered storage specialist, will spur the development of commercial-scale projects in the UK and abroad.
Said Stephen Crosher, Chief Executive of RheEnergise in a LinkedIn post: “This is the moment many customers have been waiting for, and it marks a transformative moment in our companies’ ambitions.”
The 500kW system, built on a hillside at Cornwood, near Plymouth, is RheEnergise’s first real-world test site for its long-duration energy-storage (LDES) solution
It’s situated at the Sibelco Cornwood kaolin mine, with Sibelco using the system at times of high demand and as a means to decarbonise operations.
Ben Uphill, Vice-President for Operations at Sibelco, hailed the project as a win, not only for Sibelco, but for the mining sector and beyond.
He said: “This exciting and innovative project wholly aligns with Sibelco’s sustainability goals. Its commercial deployment in the global mining sector and within other industrial applications can support the world’s transition to a zero-carbon economy.”
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RheEnergise is developing what it refers to as high-density hydro, a form of LDES technology that delivers pumped hydro-like performance but on much smaller sites.
The company’s proprietary HD Hydro energy storage system uses a specially formulated, low-viscosity, denser-than-water fluid. They worked with UK-based manufacturer 42 Technology (42T) to design and develop a semi-automated processing plant to manufacture the fluid.
The fluid is 2.5 times denser than water, which means storage plants require significantly smaller height differences between their upper and lower reservoirs, says 42T. This enables installations on hills rather than mountains, and allows for faster, more scalable and cost-effective deployment.
Crosher and the RheEnergise team are now focusing on next steps. “We have proven and critically de-risked our High-Density Hydro® technology which will allow us to focus on deploying the solution in commercial-scale LDES schemes in the UK and worldwide.
“The future of long-life, low-cost energy storage is in the hills of Devon,” concluded Crosher.
