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High-density pumped hydro ‘could be installed on thousands of small hills’

Professional Engineering

Unlike conventional hydro power systems, the RheEnergise systems could operate across smaller elevation changes (Credit: RheEnergise)
Unlike conventional hydro power systems, the RheEnergise systems could operate across smaller elevation changes (Credit: RheEnergise)

Thousands of hillsides around the UK could host a new type of pumped-hydro energy storage system, its developers have claimed.

Unlike conventional hydro power, the system from RheEnergise uses dense liquid instead of water. The fluid is two-and-a-half-times denser than water, and could therefore potentially provide two-and-a-half-times the power of equivalent conventional systems.

The High-Density Hydro systems would be built underground. Its developers said it could offer long-term energy storage at relatively low costs, with high energy efficiency.

Like conventional pumped hydro, it would use excess energy – such as that generated by wind turbines on a windy day with low demand – to pump the liquid uphill from underground storage tanks. After travelling uphill through underground pipes, the liquid would then be released to power downhill turbines when electricity demand is higher.

RheEnergise said it invented the new high-density fluid, known as R-19. Chief executive Stephen Crosher told Professional Engineering that the liquid is a fine-milled suspended solid in water, with low viscosity and low abrasion characteristics. The base material is used in oral medication applications, in a similar way that chalk is used as a bulking agent for pills and tablets. He said the raw materials are common and available, including in the UK, and the fluid could either be manufactured on-site or at a depot. 

The firm is running a crowdfunding campaign to fund the next phase of its work. Two weeks after opening to the public, it has secured more than £320,000. The company aims to have its first commercial system operating in 2024, and over 100 systems within the next decade.

Conventional low-density hydro power systems operate in the Scottish Highlands, Wales and across Europe, but natural limitations mean scope for further expansion is limited. RheEnergise said its system could instead operate beneath small hills, requiring less vertical elevation. The firm said this would open up many more potential sites – about 9,500 in the UK, 80,000 in Europe and 160,000 in Africa.

A large increase in energy storage is required in the UK and around the world, to ensure consistent supply from intermittent renewable sources. In the UK, Aurora Energy Research forecast an additional 13GW storage requirement by 2030. Last week, trade association Renewable UK said the total capacity of the energy storage ‘pipeline’ is more than 22GW.

Crosher of RheEnergise said: “We offer a neat, low-cost, zero-carbon and scalable solution to meet the energy storage needs of this country and across the world.  Energy storage, like our HD Hydro system, will enable the increased deployment of wind and solar generation to achieve the energy transition.”

Each system would require planning consent and could have an operational life of more than 60 years. They could offer between 5MW and 100MW of power.

The company’s crowdfunding campaign will help to finance a 500kW test rig, likely to be located in Cumbernauld, in Scotland’s Central Belt. R&D work to date has been part-funded by Innovate UK, with eight grants totalling £550,000 and a further ongoing grant of £135,000. Its work is also supported by a number of academic and research organisations, including Exeter University, Camborne School of Mines, the Science & Technology Facilities Council, the National Engineering Laboratory and Eminox, a specialist engineering company based in Gainsborough, Lincolnshire.

“Flexible technologies like HD Hydro will form part of the UK’s smart electricity grid, supporting the integration of more low-carbon power, heat and transport technologies, which BEIS (the Department for Business, Energy & Industrial Strategy) estimates could save the UK energy system up to £40bn by 2050,” said Crosher.

“Whilst our underground hillside technology opens up a massive amount of opportunity, we acknowledge the need for careful planning and stringent environmental assessments. Not every hillside location will be suitable.”


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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers. 

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