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Gain exclusive insights in an Interview with Stephen Crosher, CEO of RheEnergise

As the world pivots towards renewable energy, the spotlight intensifies on energy storage, a crucial element in addressing the intermittency of green power sources. Positioned at the heart of the global energy transition, this sector is on the brink of becoming a multi-trillion-dollar market, driven by the need for stable, reliable power grids.

This interview explores the transformative potential of RheEnergise's High-Density Hydro®, highlighting their pivotal role in shaping a sustainable future. Discover the innovations steering us towards a zero-emission world through the lens of industry experts and groundbreaking technologies.

Energy storage is set to be a multi-trillion-dollar market, could you explain why?

Governments across the world have recognised the urgency to completely decarbonise over the next 30 years. To decarbonise, countries must redesign their power systems, switching from coal, oil and gas to renewables. Renewable power is generally more distributed, more local but it is intermittent. Energy storage is the solution to intermittency and will help keep power grids stable and reliable.

Industry experts across the world, including Bloomberg New Energy Finance, IRENA, The Long Duration Energy Storage Council, McKinsey, Jacobs, Accademia, and many others have predicted this trillion-dollar market.

Malcolm Turnbull, a former Australian Prime Minister and President of the International Hydropower Association said “When we talk about the transition to a zero-emission energy system, we often overlook the crisis within the crisis, and that is long duration storage”

And Katie Fehrenbacher said, which I wholly agree with “A next generation smart grid without energy storage is like a computer without a hard drive: severely limited.”


To put the scale of the challenge into perspective, the world needs in the order of 2,000GW of energy storage, that can provide power for 10 hours at a time. This amount of new energy storage is at least ten times the current amount available. Batteries, despite their recent growth, still make up a tiny proportion of the total energy storge, other solutions are needed alongside.

Most people think of batteries when they think of energy storage, can you explain how your High-Density Hydro® solution works and why is it better?

Batteries are an ideal solution for shorter durations of energy storage (for up to say 3 hours) and are good at providing ancillary services such as frequency response. However, with batteries, for every MW of power one purchases, one gets about MWh of storage i.e. the storage lasts for 1 hour. This means that to get lots of MWhs, or long durations of storage, project sizes, the number of batteries and the costs increase.

Our solution at RheEnergise is different because the power component is decoupled from the storage component. The power is defined by the size of the pipes from the top to the bottom of the hill and the size of the turbines, whilst the energy or duration is defined by the size of the storage tanks and fluid volume. This means that one can set the power one requires and set the duration without oversizing any part of the project.

The lowest cost form of energy storage, for long durations, by far is traditional pumped hydro. It is a very mature technology that has been around for over 100 years. What RheEnergise achieves with its High-Density Hydro® is the same low cost of storage as traditional pumped hydro, but it creates vastly more siting opportunities for projects. This is because HD Hydro uses a fluid that is 2.5 times the density of water (about the density of concrete). With High-Density Hydro® the same performance can be achieved on small hills rather than mountains, when compared to projects using water. This means that there are hundreds of thousands of sites available across the world and sites are close to where they are needed.

To summarise, High Density Hydro presents the ultra-low costs of storage associated with pumped hydro, while dramatically increasing the number of sites available and it also speeds up construction times, so that projects are built in the same sort of time scales as other energy projects – wind, solar, batteries etc.


You are in the middle of a fundraising round on Crowdcube, what are you using the capital from the funding campaign for?

We are fundraising on CrowdCube, but we are also taking direct investments from innovation funds, family offices and also some individuals. It is worth noting that this round is being led by a UK investor call the Low Carbon Innovation Fund, who are highly experienced with 37 investments in total. The LCIF fund managers undertook extensive due diligence on us [RheEnergise].

We are using the funds to back up the extensive amounts of non-dilutive capital available to the company, which totals over £11m of grants and government contracts to date. This is four times the equity invested to date – we think that’s a good and attractive ratio. We also have strong signs that a further £1m will be added in the next few weeks and have recently made some further grant applications.

The grants pay for our 500kW demonstration projects 100%. We are using the money raised, alongside these grants to continue to grow our R&D capabilities to keep our moving forward on the progress towards a fully commercial product; to grow our engagement with customers, to strengthen our IP portfolio and to provide the business wrap to ensure that the grant funded projects are successfully delivered.


Where are you targeting as your first markets? 

Energy markets across the world are transitioning. In the last year we have secured interest from developers and utilities. In the UK, we have signed a Memorandum of Understanding (MOU) with Mercia Power Response. Australia is on our target list where we have already signed a Letter of Intent with a developer looking at a project in Queensland. We have also signed an MOU with Colbún, a leading utility in Chile. This is enough for now, we must keep focus, however we are aware that there is strong interest from elsewhere: Parts of the US could really do with our solution – California, New York, Texas. Mexico has so many suitable project sites, as do places like Turkey or even Saudi-Arabia.

Early customers might be large energy consumers with 24/7 power demands, such as mines and quarries, that wish to both manage their energy costs and decarbonise.

Our challenge is to keep focus on the most attractive markets. There are many potential markets, and the numbers are clearly growing every year as renewable energy penetration increases in many countries across the world. Our second challenge is how to move fast enough to address these growing opportunities that exist across the world, and to do that a bigger team would help, hence the ask for people to look at our investment proposition, either on CC or for larger investors contact us directly.

To gain further information regarding this investment opportunity, register for our exclusive investor roundtable via Zoom on the 20th February 2024 at 1 PM.

If you would like to know more about work and our Crowdcube fundraising opportunity, please register via this link or contact us via

Investment risk warning: Don’t invest unless you’re prepared to lose all the money you invest. This is a high-risk investment and you are unlikely to be protected if something goes wrong. Take 2 mins to learn more.


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