A British flow battery spinout that spent eight years in the lab has been handed GBP 10 million by the UK state development bank to prove its chemistry can hold grid power for days rather than hours.

Certain Energy closed a GBP 10 million Series A on Aug 26, 2026, reported as roughly USD 13.62 million and EUR 11.6 million. The British Business Bank put in GBP 3.5 million and led the round according to most outlets covering the deal, alongside Centrica, Ceres Power Holdings and Temasek Trust Catalytic Capital for Climate and Health (C3H). TNGlobal instead frames C3H as the lead. Valuation was not disclosed. The VentureTerminal feed lists the round at USD 13M, slightly below the converted figure in press coverage, and names no lead.

What Certain Energy does

The company was known as RFC Power until this week. It was spun out of Imperial College London in 2017 on work by chemistry professor Anthony Kucernak and engineering professor Nigel Brandon, with Javier Rubio Garcia and Vladimir Yufit also named on the founding science. It builds hydrogen manganese flow batteries. A flow battery keeps its energy in liquid electrolyte held in external tanks and its power in a separate cell stack, so duration is a function of tank size. Adding hours means adding electrolyte, which is where the cost argument lives.

Certain Energy claims round trip efficiency above 75 percent, a patented electrolyte designed for a 20 year operating life with minimal capacity degradation, and marginal storage costs around one tenth of vanadium flow systems. Manganese is the reason: cheap, abundant and non toxic, where vanadium is a thinly traded commodity whose price history has made project finance difficult.

The numbers behind the round

Of the GBP 10 million, GBP 3.5 million came from the British Business Bank. Ceres Power, itself an Imperial spinout and a listed fuel cell developer, is an existing shareholder. Centrica brings a utility route to market. Prior disclosed funding is thin: IP Group backed a seed round announced in January 2020 without a stated figure, and the company has not published a cumulative total. The new money is earmarked for a grid connected MWh class system in India, expansion of the UK research facility, and building a supply chain capable of repeating projects rather than one offs.

Why the timing matters

UK renewable curtailment, paying wind farms to switch off when the grid cannot absorb their output, could cost GBP 8 billion a year by 2030 without long duration storage. Lithium iron phosphate has taken the one to four hour market and is not economic much beyond it. That leaves a gap between a day of surplus wind and the week of low wind that follows, which is the gap flow chemistries are meant to fill. Energy minister Michael Shanks tied the investment to British innovation and to storage measured in days.

The caution is that the round is small for hardware. An MWh class demonstration is a step past the lab but well short of the grid scale deployments that decide whether a chemistry wins. Chief executive Tim von Werne put the bet plainly: long duration storage is the missing piece of the clean energy system, and manganese flow is the technology that should win. GBP 10 million buys the chance to test that, not to settle it.

Source

Solar Power Portal — "British Business Bank backs UK LDES company Certain Energy"