Britain’s renewable energy boom has a costly side effect: on windy, sunny days when the grid can’t absorb all the power being generated, operators pay wind and solar farms to switch off. That curtailment bill hit roughly £1.5 billion last year, and could climb as high as £8 billion annually by 2030 if the grid isn’t given somewhere to put the surplus, according to Certain Energy executive chair Mark Selby.
Certain Energy — until this week known as RFC Power — is betting that manganese-based flow batteries are that missing piece. The Imperial College London spin-out has closed a £10 million ($13.6m/€11.6m) Series A round, led by the British Business Bank, and used the announcement to formally retire the RFC Power name.
From lab bench to grid-scale
The company traces back to 2017, when it was spun out of Imperial’s White City innovation hub to commercialise flow battery research from Professor Anthony Kucernak in the Department of Chemistry and Professor Nigel Brandon in the Department of Earth Science and Engineering, alongside researchers Javier Rubio Garcia and Vladimir Yufit. It has since operated out of Imperial’s I-HUB with backing from the Imperial Incubator and The Greenhouse accelerator.
Rather than the vanadium chemistry most flow batteries rely on, Certain Energy uses manganese — the twelfth most abundant element in the Earth’s crust — paired with a hydrogen-manganese cell design the company says is globally patented. Because flow batteries store their energy in liquid electrolyte held in external tanks rather than in the electrode stack itself, power output and storage duration can be scaled independently: adding hours or days of extra capacity is largely a matter of installing bigger tanks, not building new factories.
Certain Energy claims round-trip efficiency above 75%, a 20-year operating life with minimal capacity fade, and a marginal storage cost it puts at roughly a tenth of comparable vanadium systems — with a long-term target of under $20 per kWh. On its website, the company frames the pitch bluntly: “scaling means bigger tanks, not bigger factories.”
Who’s backing the round
The £10 million round was led by the British Business Bank, which put in £3.5 million, alongside energy supplier Centrica, Ceres Power Holdings — the fuel-cell group that previously held a stake in the business as RFC Power — and Temasek Trust’s Catalytic Capital for Climate and Health (C3H), a Singapore-linked impact investment vehicle.
Charlotte Lawrence of the British Business Bank pointed to volatile grid supply and demand worldwide as the reason long-duration storage now stacks up financially, not just environmentally.
Dr Tim von Werne, Certain Energy’s chief executive, framed the funding as validation of the underlying chemistry rather than just the balance sheet: “Long-duration storage is the missing piece of the clean energy system, and manganese flow is the technology that should win.”
Where the money goes
Certain Energy says the funding will go toward three things: commercialising the manganese flow technology at volume, expanding its UK research facilities, and building out a grid-connected, megawatt-hour-class demonstration system in India — a market the company is treating as a proving ground for deployments that can be replicated elsewhere.
The rebrand itself is part of the pitch. Trading as Certain Energy rather than RFC Power, the company is positioning itself less as a lab-spun chemistry project and more as infrastructure for what it calls “the transition to 100% renewable energy” — storing not just hours of surplus power, but potentially days of it, to give grid operators an alternative to paying wind farms to stand idle.
For a UK grid straining to absorb record renewable output without record curtailment bills, that’s the problem Certain Energy is now trying to prove it can solve at scale.
