In partnership with the University of Greenwich and the University of Exeter, RheEnergise, the UK company that is developing a new and advanced form of pumped hydro-energy storage, has secured a grant of £1 million funded through the Net Zero Innovation Portfolio (NZIP) as part of the UK Government’s Energy Entrepreneurs Fund.  The government grant will fund work to identify and test waste materials that could be used in the high-density fluid (HDF) that is integral to RheEnergise’s grid-scale High-Density Hydro® energy storage system. The HDF is an environmentally benign alternative to water. 

RheEnergise’s long duration storage system is low-cost and energy efficient. The fluid used in the system is 2½ times denser than water (similar in viscosity to cream) and is therefore able to provide 2½ times the power and 2½ times the energy when compared to conventional low-density hydro-power systems that rely on water and operate in the Scottish Highlands, Wales and across Europe.  It means that RheEnergise can deploy its long duration energy storage system beneath the surface of hills rather than mountains, so opening up massive commercial opportunities in the UK, Europe and further afield. 

The research project, funded by the Department for Energy Security & Net Zero's Energy Entrepreneurs Fund, wants to identify suitable minerals and waste streams which can be recycled into the high-density fluid which can be locally sourced and are lower-cost, rather than having to rely on minerals imported from overseas. 

Stephen Crosher, Chief Executive of RheEnergise says: “The opportunities presented by the EEF grant are phenomenal. We are delighted to be able to lead and partner with two outstanding universities - Greenwich and Exeter. The project has the potential to solve three huge questions that affect people daily and globally: those of climate change mitigation, delivering firm power supply from renewables and how to use waste from other industries for new purposes, creating truly circular economies.” 

“The government grant, from the Department for Energy Security & Net Zero, will help us to cut the operating cost of our hydro energy storage system, whilst increasing its sustainability. By using locally sourced waste materials, we can lower the costs of our projects, reduce carbon emissions from transportation and processing and create a new circular economy where none currently exists.”

“Working with colleagues from Greenwich and Exeter Universities, our research team will be closely examining waste and tailings from various sources but in particular from mines and quarries. There is also the potential that operating mines and quarries, which by their very nature have high elevations and are high energy users, could use our energy storage system.” 

Graham Stuart MP, UK Energy Minister said: 

“This funding will see the next generation of energy pioneers drive forward cheap and sustainable low-carbon technologies.    

“This will not only deliver green jobs and lower the costs of energy to businesses but also foster world-leading solutions to net zero and economic growth.”   

Later this year, RheEnergise will start work on building a 250kW/1MWh (4 hours) demonstrator of its High-Density Hydro® energy storage system at a site near Plymouth (announced in November 2022) and is planning to have its first 5MW grid-scale project in commercial operation within the next 3-5 years. 

Notes to Editors:

How the HD Hydro system works: at times of low energy demand, with associated low costs, the High-Density Fluid R-19™ is pumped uphill between storage tanks (buried underground). The storage tanks are connected by underground pipes. As energy prices rise, the non-corrosive fluid is released downhill and passes through turbines, generating electricity to supply power to the grid.  Projects will range from 5MW to 100MW of power and can work with vertical elevations as low as 100m or less. It means that, unlike conventional pumped hydro energy storage, a RheEnergise HD Hydro system can operate beneath small hills rather than mountains; the system requires 2½ times less vertical elevation. It also means that there are many more sites suitable for RheEnergise projects – in the UK and across the world. 

RheEnergise’s analysis of potential project opportunities has indicated that there are c6500 site opportunities in the UK, c115,000 in Europe, c345,000 in North America and c500,000 in Africa and the Middle East. 



In November 2022, RheEnergise was awarded a UK £8.25m small business research initiative (SBRI) contract from the UK Government’s Net Zero Innovation Portfolio (NZIP) to deploy a first-of-a-kind demonstrator at a site near Plymouth, Devon.

About the Department for Energy Security & Net Zero 

‘Leading economy-wide transformation by backing enterprise and long-term growth, generating cheaper, cleaner, homegrown energy and unleashing the UK as a science superpower through innovation.   

Funded through the Government’s £1 billion Net Zero Innovation Portfolio, which provides funding for low-carbon technologies and systems. Decreasing the costs of decarbonisation, the Portfolio will help enable the UK to end its contribution to climate change.’