British Business Bank has led a £10 million Series A funding round for Certain Energy, formerly known as RFC Power, to commercialise its manganese electrolyte flow battery technology for long-duration energy storage.

Certain Energy is a spin-off from Imperial College London, founded in 2017 and based in the UK; the company does not disclose turnover or profit. The round included Centrica, the British Gas owner that reported £19.9 billion revenue for 2024, Ceres Power Holdings, the Horsham-based fuel cell developer of which Certain Energy was formerly a subsidiary and which posted revenue of £51.9 million for 2024, and the Temasek Trust's Catalytic Capital impact fund.

The state-owned British Business Bank contributed £3.5 million of the total round. Certain Energy's flow batteries decouple power and energy by separating electrolyte tanks from the cell stack, allowing storage capacity to scale up independently of power output to increase duration.

Certain Energy says its patented electrolyte achieves a 75% round-trip efficiency, positioning it to compete economically with lithium-ion batteries on key grid services. Other flow battery technologies, such as vanadium chemistries, can also compete with lithium-ion in longer duration deployments, though the company says its design could cut marginal storage costs to around a tenth of comparable vanadium systems, which require higher upfront capital spending.

The structural driver is the UK's rising renewable curtailment bill, which Certain Energy warns could reach £8 billion annually by 2030 without new long-duration storage capacity to absorb power when the grid cannot accept it.

With the new funding, Certain Energy will develop a grid-connected megawatt-hour class system in India, expand its UK research facility and build a supply chain to deliver replicable projects. The batteries are designed for a 20-year operating life with minimal capacity degradation.

"The renewable power market is held back by its vulnerability to external factors," said Mike Selby, Certain Energy's executive chair. "The answer is long duration energy storage and Certain Energy has the technology and now the funding to deliver highly efficient, affordable batteries, based on abundant materials, to make this a reality."

For the sector, the round signals growing investor confidence in flow battery chemistries beyond vanadium, with government-backed capital increasingly targeting the long-duration storage gap that renewables curtailment costs are making commercially urgent.

Source: solarpowerportal.co.uk / energy-storage.news / finance.yahoo.com