UK startup wins €2.5m grant for green energy storage breakthrough
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RheEnergise, a UK-based energy startup, has secured €2.5 million (£2.15 million) from the European Innovation Council (EIC) Accelerator to develop its pioneering High-Density Hydro® energy storage technology. As one of only three British firms to receive support in this funding round, and the sole long-duration energy storage (LDES) company included, the grant marks a significant milestone in Europe’s clean energy investment agenda.
The EIC grant recognises the commercial promise of RheEnergise’s approach to storing electricity using pumped hydro principles re-engineered with a proprietary dense fluid. The funding will be used to support ongoing research and development activities for the company’s first commercial deployment, reinforcing the strategic relevance of alternative LDES technologies in a continent moving toward grid decarbonisation.
Rethinking pumped hydro: How dense fluid changes the rules
Traditional pumped hydro systems rely on water reservoirs positioned at significant elevation. RheEnergise’s solution breaks this geographical constraint by introducing a fluid approximately 2.5 times denser than water. This High-Density Hydro® system enables energy storage to be installed on hills as low as 100 meters in height, vastly increasing the number of viable sites across the UK and beyond.
By using their proprietary HD Fluid R-19™, the company can store and dispatch electricity with enhanced efficiency and capacity. The approach provides modular, scalable systems ranging from 10 to 100 megawatts, offering a more flexible solution compared to traditional pumped hydro schemes that often require decades-long planning and gigawatt-scale infrastructure.
Pilot project in Devon signals commercial readiness
The company’s flagship demonstrator project is already under development near Cornwood, just outside Plymouth in Devon. Backed by the UK Department for Energy Security & Net Zero, the site will serve as the operational testbed for RheEnergise’s commercialisation strategy.
This installation aims to validate both the technological and economic viability of High-Density Hydro® at scale. It also represents one of the few new LDES assets under construction in the UK in recent years, a country that has not built a new large-scale pumped hydro facility for nearly four decades.
The Cornwood project is expected to begin pumping operations soon and will serve as a blueprint for future deployments, both domestically and abroad.
A versatile model for global clean energy markets
With initial traction secured in the UK, RheEnergise is already laying the groundwork for international expansion. Project agreements are in place in South America, Australia, mainland Europe and other regions, supported by an active investment roadshow in Canada.
The technology’s modularity and compact siting requirements make it particularly well-suited for regions where conventional hydro is impractical. Co-location opportunities with wind and solar farms, and proximity to industrial energy demand centres such as data centres, broaden the market appeal further.
Unlike large-scale pumped hydro projects that often face planning and environmental hurdles, RheEnergise’s systems are designed to integrate discreetly into rural landscapes with minimal impact.
The long-duration energy storage gap and RheEnergise’s opportunity
The UK’s energy system increasingly depends on renewables, but long-duration storage remains underdeveloped. Current hydropower accounts for just 2 percent of electricity generation, and the last major pumped hydro development was commissioned in the 1980s.
Policy efforts are now catching up, with the government targeting 11 to 15 gigawatts of long-duration storage capacity by 2050. Initiatives such as Ofgem’s cap-and-floor mechanism for storage and targeted innovation grants are building momentum. RheEnergise’s High-Density Hydro® is positioned to capitalise on this strategic shift, filling a gap between utility-scale pumped hydro and shorter-duration battery systems.
As the energy transition advances, cost-effective, site-flexible, and scalable storage solutions will be key. With European backing and growing international interest, RheEnergise is poised to play a central role in defining the next generation of energy infrastructure.
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