Certain Energy banks £10m to scale long-duration storage

A London storage developer spun out of Imperial College in 2017 has raised £10 million (US$13.6 million) in a Series A led by the British Business Bank, putting direct transition-finance capital behind a manganese-based long-duration flow battery. The round, announced August 26, also drew Centrica, Ceres Power Holdings and Temasek Trust's Catalytic Capital for Climate and Health — a cap table with the look of a deal built to be replicated.

Certain Energy, formerly RFC Power, develops manganese-based flow batteries that store clean energy for hours to days; manganese is the twelfth most abundant element in the Earth's crust. Designed to stabilise grids and supply power during low-renewables periods, the system extends discharge by increasing electrolyte tank size rather than packing in more cells. The company claims round-trip efficiency above 75%, and says the material mix could pull marginal storage costs to about a tenth of comparable vanadium flow batteries and below lithium-ion for key grid services.

The proceeds target volume production: a grid-connected MWh-class system in India, expanded UK research facilities and a supply chain built for replicable projects. Executive chair Mark Selby framed the market in curtailment terms — the UK government spent around £1.5 billion last year paying renewable generators to shut down in peak periods, and the grid operator expects that to climb toward £8 billion a year by 2030. Long-duration storage is the obvious release valve for that spending, and this round is a modest early bet against the bill.

Certain Energy has named its chemistry, its efficiency threshold, its cost target and its first deployment site, and the cap table is the structure transition finance needs to repeat. The British Business Bank anchored a round that Centrica, Ceres Power Holdings and Temasek Trust's Catalytic Capital for Climate and Health all joined, a combination that prices hard-to-abate grid risk before the India system proves its cost curve — a firmer underwriting than most labeled bonds deliver.

Curtailment is becoming a line item on grid operators' books wherever renewable penetration climbs, and storage has been hard to underwrite because its economics turn on chemistry and manufacturing scale at the same time. A manganese battery that hits the claimed numbers will make the next round for a comparable developer a simpler conversation; one that misses will make the class harder to price. The next developer will know the anchor investor's name and which numbers were priced.