RheEnergise

What RheEnergise does

RheEnergise Limited is a UK-based long-duration energy storage technology company, founded in 2019 and headquartered in London with a wholly owned Canadian engineering subsidiary in Montreal. It develops and commercialises High-Density Hydro® (HD Hydro®), a pumped hydro energy storage system that uses a patented high-density, low-viscosity working fluid approximately 2.5x denser than water. This fluid density advantage allows RheEnergise to deploy storage installations on hillsides rather than requiring mountain topography, materially expanding the addressable site base compared to conventional pumped hydro. The system targets 10–100 MW capacity at 6–20 hours of storage duration and comprises six integrated sub-systems including the proprietary HD Turbine, storage tanks (which can be buried), underground penstocks, and power-conversion equipment.

The company's first commercial deployment — a 500kW system at Sibelco's kaolin mine near Plymouth — reached full power in January 2026, validating core technology after consistent cycle testing. RheEnergise positions HD Hydro as half the levelised cost of lithium-ion batteries at 8-hour duration, with a 60+ year asset life and no factory CAPEX required because it leverages existing global hydropower supply chains (notably a manufacturing partnership with Hydropower Engineering in Turkey for the first-of-a-kind turbine). Its intellectual property base of 20 patents across 11 families and the registered HD Hydro® trademark underpin the technology moat.

RheEnergise operates as an enterprise solution provider, targeting renewable energy developers, independent power producers, utilities, infrastructure operators, data centre operators and mining operators across 25+ countries. The go-to-market is direct and relationship-led, with the company co-identifying viable sites, providing performance and cost data, and facilitating development. Pricing is bespoke per project; at the project economics level, a co-located solar and HD Hydro data centre project in Texas is reported to deliver a 16.7% internal rate of return and ~6.5-year payback. The company is pre-revenue, has raised roughly £5M of equity alongside ~£36M of grants, and is currently expanding its commercial pipeline and team following the successful Cornwood demonstration.

Name

RheEnergise

Legal name

RheEnergise Limited

Website

https://rheenergise.com

Company type

Private

Founded year

2019

Operating status

Operating

Headcount range

11–50 employees

Short description

RheEnergise develops and commercialises High-Density Hydro® (HD Hydro®) long-duration energy storage technology, using a proprietary fluid 2.5x denser than water to enable pumped hydro storage on hillsides. It serves renewable energy developers, utilities, mining operators and data centres across 25+ countries.

Ownership category

akta.pro rank

Product category

Long-Duration Energy Storage

NAICS

Hydroelectric Power Generation (221111), Electric Power Generation, Transmission and Distribution (2211)

SIC

Cogeneration Services & Small Power Producers (4991)

akta.pro primary industry

Mechanical LDES (Pumped Hydro, Compressed/Liquid Air, Flywheels) (EUAFADAB)

akta.pro secondary industries

LDES Systems Integration, EPC & Project Development (EUAFADAG), Pumped-Storage Hydroelectric Generation (EUACAEAC), Energy Storage Asset Management (BESS/PCS/EMS) (EUAEAMAE), LDES Financing, Insurance & Revenue Optimization (Capacity/Ancillary/Arbitrage) (EUAFADAK)

Keywords

• Long-duration energy storage
• Pumped hydro storage
• Grid-scale storage systems
• Renewable energy infrastructure
• High-density hydro technology

Headquarters

HQ city

London

HQ country

United Kingdom

HQ region

Europe

Offices3 records

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Personnel, Technology or R&D, Operations, Supply Chain, Infrastructure, Marketing or Sales

Revenue model

1. LDES Project Development: RheEnergise operates as a solution provider with 3 key phases in delivery: technical know-how and fully integrated product to customers, utilizing existing global manufacturing supply chains. Revenue generated through development, financing and construction of commercial-scale LDES projects.

Pricing tiers

Go-to-market motion1 record

Distribution channels1 record

Marketing channels6 records

Core offering

RheEnergise designs and delivers High-Density Hydro® (HD Hydro®) long-duration energy storage systems that use a proprietary high-density fluid (2.5x denser than water) to enable pumped hydro energy storage on hillsides rather than mountains. The company operates as a solution provider, delivering technical know-how and fully integrated 4-16+ hour energy storage systems (10-100 MW target capacity) to enterprise customers including utilities, mining operators, data centers, and renewable energy developers, leveraging existing global supply chains for project development, financing, and construction.

Product overview

RheEnergise offers a single unified product: the High-Density Hydro® (HD Hydro®) energy storage system. This is a next-generation pumped hydro technology that uses a proprietary high-density fluid (2.5x denser than water) to store energy on hillsides rather than mountains. The HD Hydro System comprises six sub-systems including the HD Turbine, storage tanks, penstocks, and power conversion equipment. The solution targets commercial-scale LDES projects (10-100 MW capacity, 6-20 hours duration) for utilities, renewable energy developers, data centers, and industrial applications. RheEnergise operates as a solution provider, delivering technical know-how and fully integrated systems to customers utilizing existing global supply chains.

Differentiator

Problem solved

Functional benefit

Brands

• High-Density Hydro® (HD Hydro®): Proprietary pumped hydro energy storage technology using a high-density fluid 2.5x denser than water, enabling installations on hills rather than mountains

Products and services

• High-Density Hydro® (HD Hydro®) Energy Storage System Proprietary pumped hydro energy storage system using a high-density, low-viscosity fluid (2.5x denser than water) that enables energy storage on hillsides rather than mountains. Delivers 4-16+ hours of energy storage at half the levelised cost of lithium-ion batteries at 8-hour duration, with a 60+ year asset lifetime and no fire/environmental risks. Targets 10-100 MW commercial-scale LDES projects for utilities, renewable energy developers, data centres, and mining operators.
• HD Hydro Demonstration & Project Development Services Turnkey project development service covering co-identification of viable sites, performance and cost modelling, financing arrangement, and construction of commercial-scale HD Hydro installations for enterprise customers. First project at Sibelco's Cornwood kaolin mine near Plymouth validates the technology and execution approach.

Quantifiable outcome

• 500kW peak power production at Cornwood project - equivalent to powering 400 homes for one year
• +3 more outcomes

Named customers3 records

Segments4 records

Ideal customer profiles4 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature3 records

Partnerships

Seven partnerships are on record, tiered strategic, core and major.

• Anglesey Mining plcstrategicStrategic or Co-development Partner · 18 February 2025MOU to explore potential deployment of HD Hydro energy storage technology at Parys Mountain mine site, utilizing underground space for energy storage.
• SibelcocoreStrategic or Co-development Partner · 29 April 2024Global mining and materials company hosting RheEnergise's first HD Hydro demonstration project at Cornwood kaolin mine near Plymouth. Sibelco's operations provide the site for the 500kW first-of-a-kind system, supporting their sustainability and decarbonisation goals.
• ColbúnmajorStrategic or Co-development Partner · 14 November 2023MOU with Chile's third-largest power generation company and prominent hydropower operator to investigate deployment of HD Hydro technology in Chile. Marks RheEnergise's first entry into South America's energy market.
• Mercia Power ResponsemajorStrategic or Co-development Partner · 15 August 2023Partnership to explore deployment of HD Hydro energy storage at Mercia Power Response's grid connections across the UK, targeting 100MW of long-duration storage capacity by 2030.
• Hydropower EngineeringcoreTechnology or IntegrationTurkish engineering company manufacturing the first-of-a-kind 500kW HD Turbine for RheEnergise's demonstration project.
• 42 TechnologystrategicImplementation/ SI/ Consulting PartnerProduct development and manufacturing innovation consultancy supporting the 500kW HD Hydro project in Cornwood near Plymouth.
• University of Greenwich and University of ExeterstrategicStrategic or Co-development PartnerUniversity partners in £1 million BEIS-funded research project to identify and test minerals and discarded wastes for use in RheEnergise's grid scale hydro energy storage system.

Scale indicators8 records

Recent moves6 records

Expansion highlights6 records

Broad incumbents

• Fluence Energy: Listed grid-scale battery storage integrator and supplier. Competes in adjacent utility and industrial storage markets; while lithium-ion focused, it is increasingly expanding into longer-duration solutions that overlap with RheEnergise's value proposition at the 8-hour crossover point.
• GE Hydro / GE Vernova: Global hydropower and grid equipment incumbent (former employer of RheEnergise board member Yves Rannou). Operates in pumped storage and grid-scale infrastructure adjacent to RheEnergise's market.
• Voith Hydro: Global incumbent in hydroelectric equipment, turbines, and pumped storage plant services. A broad incumbent whose pumped hydro expertise and customer base overlap with RheEnergise's target market and technology lineage.
• Andritz Hydro: Major incumbent in hydropower plant equipment, turbines, and pumped storage EPC. Competes indirectly for utility-scale hydro storage projects and could be a partner or competitor to RheEnergise.

Direct peers

• Energy Vault Holdings: Listed LDES company developing gravity-based and hybrid storage solutions targeting utility-scale long-duration applications. Most direct publicly traded LDES peer, competing for similar utility, data centre, and industrial customers.
• Form Energy: US-based LDES company developing iron-air battery technology for 100+ hour discharge. Directly competes for utility and grid-scale long-duration storage contracts and is well-capitalised compared to RheEnergise.
• Hydrostor: Canada-based LDES developer using advanced compressed air energy storage (A-CAES) with hydrostatic compensation. Most analogous to RheEnergise in combining underground/mining siting with bulk long-duration storage economics.
• Highview Power: UK-based LDES developer using liquid air energy storage (LAES) for long-duration grid-scale applications. A direct competitor in the European LDES market targeting utilities and industrial customers with comparable multi-hour storage offerings.

Emerging players

• Malta Inc. US-based LDES developer using pumped heat energy storage (PHES) for grid-scale applications. An emerging player targeting similar utility and industrial long-duration storage customers.
• Quidnet Energy: US-based LDES start-up using geomechanical pumped storage in subsurface wells. Competes in the same long-duration storage category with a similar siting-flexibility angle to RheEnergise's hillside HD Hydro.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat5 records

Key risks7 records

Key highlights7 records

Customer concentration

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Revenue estimate

Valuation estimate

Number of profiles

Profiles13 records

Subsidiaries1 record

Funding overview

Funding rounds7 records

Investors4 records

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about RheEnergise