Startup Profile


London, England

Bringing innovation to pumped energy storage with High-Density Hydro®

Company Details

Investment Deck

The Problem:

With renewable energy sources rarely aligning with the variable demand from consumers and industry, power grids become unstable, creating an urgent need for effective long-duration energy storage solutions. These solutions must not only be cost-effective but also massively scalable, a challenge that the current 170GW of long duration installed capacity falls short of addressing. The climate crisis dictates there is only 20 years to build approx. 2,000GW of long duration energy storage.

The Solution:

RheEnergise’s High-Density Hydro® storage system is an innovative, low-cost, and globally scalable energy storage solution, designed to provide 2 to 16 hours of energy storage in the 10MW to 100MW power range. Rather than using water, RheEnergise has developed an environmentally benign fluid, which is 2½ times denser than water, and which can provide 2½ times the power and 2½ times the energy when compared to a conventional low-density hydro-power system.

The Differentiator:

By replacing water with a High-Density Fluid in a closed-loop system, HD Hydro maintains comparable project economics compared to conventional water-based Pumped Hydro Storage while reducing the required vertical elevation for a project by a factor of up to 2.5x. High-Density Hydro can be developed on hills as low as 75m which unlocks an enormous number of potential sites. This allows developers to work on multiple smaller projects (10MW - 50MW) at once, achieving scale through multiple projects

Biggest Achievement:

RheEnergise was awarded an £8.25m, 100%-funded contract from UK Government, as part of the Longer Duration Energy Storage (LoDES) Demonstration Programme, to undertake the initial R&D and build its first-of-a-kind 500kW, TRL7 demonstrator of the system. The project is also being supported by Devon County Council, which has permitted the project, and the valuable co-operation and commitment to the project from Sibelco. Works are due to start imminently with commissioning scheduled for Q4 2024.

Programme themes:

Low carbon power

Team members:

Stephen Crosher


Philippa Rogers

Communications Manager

    Graham Cook