Energy storage |
RheEnergise completes main mechanicals at Cornwood
RheEnergise, the UK–Canadian company that is developing a new and advanced form of pumped hydro storage technology – employing high-density fluid (R-19) instead of water – has completed the main mechanical works at its demonstrator project at Cornwood, a few miles from Plymouth in Devon, UK. It was hoping to start LDES (long duration energy storage) operations at Cornwood this autumn, as part of the “R&D pathway to its first commercial scale project.” If development proves successful, the technology, High-Density Hydro®, is seen as being able to provide increased flexibility and security to national energy systems, facilitating the increased deployment of renewables and the transition to low carbon generation/ Net Zero.
The Cornwood demonstrator – a “real-life test laboratory” – is viewed as a key element in RheEnergise’s path to the commercial deployment of its LDES technology. Onsite work at the Cornwood demonstrator, which has been mainly funded by the UK government through DESNZ’s Long Duration Energy Demonstration programme, started last year. The main mechanicals now installed at Cornwood include the main turbine, pump and generators together with all of its piping and valves, the power conversion system, the mixing system, the fluid management system, the flow control systems and the hydraulics. The main civil engineering works, including the power-
Inside the power-house at Cornwood. Photo: RheEnergise
house, the upper and lower reservoirs and the underground pipelines, were completed earlier this year.
The work was carried out by D.A Macdonald Ltd, Friendship Engineering, and Drew & Co working alongside RheEnergise’s in-house
engineering team led by Dr Tamás Bertényi, the company’s Chief Technology Officer and a co-founder of RheEnergise.
Conventional pumped hydro storage vs RheEnergise High-Density Hydro®. Image: RheEnergise
“It’s not without challenges, but we are aiming for our first commercial projects to be built and commissioned within the next two to three years,” said Dr Bertényi
RheEnergise says it has agreements in place to deploy its technology in the UK, South America, Australia and mainland Europe. In July 2025, the company secured a £2.15m (€2.5m) grant from the European Innovation Council (EIC) Accelerator to support its R&D and is also pursuing a funding campaign in the USA and Canada.
Power rating of future commercial projects is expected to range from 10 MW to 100 MW, with the ability to work with vertical elevations as low as 100 m or less. Unlike conventional pumped hydro energy storage, a RheEnergise HD Hydro system can therefore “operate beneath small hills rather than mountains.” It means that there are many thousands more sites suitable for RheEnergise projects – in the UK and across the world – than for conventional pumped hydro. The energy storage provided by the RheEnergise technology could in theory be any duration, from about 30 minutes upwards. However, the company says the “sweet spot” is 4-20 hours.
Connected Energy sees big second-life potential in France
Connected Energy has secured grid connection for one of Europe’s largest second-life battery energy storage deployments, marking the UK company’s expansion into the French market with a 100 MWh project in Région Centre-Val de Loire. The UK-based company has established an office in Bordeaux to capitalise on the major opportunity for second-life BESS (ie, repurposing
of used electric vehicle batteries) in this market. The company expects to commission this first large scale site by 2027, with several smaller projects expected to be operational before then. “France has huge untapped potential for second-life BESS,” says Rob Moore, Chief Business Development Officer at Connected Energy. “It has available grid capacity and growing
46 | September 2025|
www.modernpowersystems.com
renewable generation which BESS can optimise, as well as other grid stability needs arising from its ageing nuclear fleet and interconnections with renewable-rich European neighbours. There is a vibrant market for energy storage developments and – critically – a strong energy trading market, making the business case for second-life BESS even more attractive.”
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