Certain Energy, an Imperial College London spin-off previously known as RFC Power, said on August 26, 2026 that it has raised a £10 million Series A round and rebranded to reflect the company's transition from R&D to commercial deployment of its manganese-based flow battery.
Who's writing the checks
The round was led by the UK government-backed British Business Bank, which contributed £3.5 million. Existing shareholder Centrica joined alongside London-listed fuel-cell specialist Ceres Power Holdings — of which Certain Energy was previously a subsidiary — and Temasek Trust's Catalytic Capital (C3H) impact fund. UK Energy Minister Michael Shanks called the investment a bet on 'British innovation' that will help develop long-duration storage to 'store clean power for days, not hours.'
How the manganese flow battery works
Flow batteries store energy in liquid electrolytes held in external tanks, which are pumped through a central cell stack when the system charges or discharges. Because power (stack size) and energy (tank size) are decoupled, capacity can be scaled independently of power rating — a key advantage for multi-hour and multi-day storage. Certain Energy's patented electrolyte uses abundant manganese and claims a 75% round-trip efficiency competitive with lithium-ion on key grid services, alongside a 20-year design life and marginal storage costs the company says can reach roughly one-tenth those of comparable vanadium flow batteries.
Where the money goes
Certain Energy will use the proceeds to develop a grid-connected MWh-class demonstration system in India, expand its UK research facility and build the supply chain needed to deliver replicable projects at scale. Executive chair Mike Selby said the UK 'renewable power market is held back by its vulnerability to external factors,' noting that the cost of curtailing British renewable generation could reach £8 billion annually by 2030 if long-duration storage is not deployed.
LDES tailwind in the UK
The round lands as the UK government pushes long-duration energy storage up the policy agenda, including cap-and-floor revenue mechanisms and Innovate UK's £3 million ultra-LDES funding call. It also joins a run of European storage deals this month, from Greenvolt's €218 million UniCredit package for two Polish BESS projects to Copenhagen Infrastructure Partners' 500 MW / 1,000 MWh Coalburn facility in Scotland.
Certain Energy was founded in 2017 as a spin-off from Imperial College London. Rival flow-battery approaches include vanadium redox from Invinity and Largo, iron-air from Form Energy and zinc-based systems from Eos Energy Enterprises.
Reporting based on coverage from Solar Power Portal, TaiyangNews, Renewable Energy Magazine and EU-Startups.