Certain Energy (previously known as RFC Power), a long-duration energy storage startup developing manganese flow battery technology, has raised €11.6 million (£10 million) in Series A funding to commercialise its technology and prepare it for grid-scale deployment.
The round was led by the British Business Bank, which invested €4 million (£3.5 million), with participation from Centrica Energy, Ceres Power Holdings plc, and Temasek Trust’s Catalytic Capital for Climate and Health (C3H).
“The renewable power market is held back by its vulnerability to external factors. Last year, the UK Government spent around £1.5 billion asking renewable energy providers to shut off their operations during peak production, and left unaddressed, the grid operator expects that to climb towards £8 billion a year by 2030.
“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,” says Mark Selby, Executive Chair of Certain Energy.
Certain Energy’s Series A lands amid notable investment in European energy-storage and grid-flexibility companies in 2026. EU-Startups has reported at least €167 million across seven comparable or adjacent rounds, including Amsterdam-based Ore Energy’s €37.3 million Series A for iron-air long-duration batteries, Oslo-based Photoncycle’s €15 million Series A for seasonal energy storage, and Munich-based encosa’s €25 million Seed round for commercial battery-storage systems.
In the UK, Edinburgh-based Exergy3 raised €11.4 million for thermal energy storage and London-based Gaussion secured €24.5 million for battery energy-intelligence technology, providing two same-country comparators.
“With grid demand and supply becoming increasingly volatile worldwide, the financial and strategic value of long-duration energy storage is clear. Certain Energy’s technology delivers a compelling return on investment whilst reducing overall energy needs. This funding will support the team in commercialising their solution and accelerating its deployment,” adds Charlotte Lawrence, Managing Director and Head of Direct Equity at the British Business Bank.
Founded in 2017 as a spinout from Imperial College London, Certain Energy is developing long-duration energy storage (LDES) systems designed to capture renewable electricity when generation is high and release it when production from sources such as wind and solar falls.
Its technology is intended to address one of the challenges associated with the growing share of renewables in electricity grids: supply and demand do not always occur at the same time. During periods of high renewable generation, electricity can exceed what the grid is able to use, while periods of limited wind or sunlight can create shortages that require other forms of generation to fill the gap.
Certain Energy is approaching this issue with flow batteries based on manganese, which the company describes as the twelfth most abundant element in the Earth’s crust.
Unlike conventional batteries, flow batteries store energy in liquid electrolytes held in external tanks. Increasing the size of these tanks can extend the amount of time for which energy can be stored and discharged, making the technology suitable for storage lasting from hours to days.
The company says its system is designed for an operating life of around 20 years, with limited capacity degradation and round-trip efficiency of more than 75%.
According to Certain Energy, its design and use of manganese could also reduce marginal storage costs to around one-tenth of those associated with comparable vanadium flow battery systems.
Certain Energy is positioning the technology as a complement and potential alternative to lithium-ion batteries for grid applications where longer storage periods are required. In addition to storing renewable power, the systems are designed to support grid reserve functions and reduce the need for gas-fired peaker plants during periods of limited renewable generation.
“Homegrown clean energy is our route to more affordable bills and energy security, and storing it for when we need it most is critical.
“By investing £3.5 million in Certain Energy, the British Business Bank is backing British innovation and helping develop the long-duration energy storage we need to store clean power for days, not hours, and deliver a more secure energy system,” says Energy Minister Michael Shanks.
The funding comes as energy systems increase their reliance on intermittent renewable generation, placing greater emphasis on technologies capable of moving electricity across longer periods rather than only balancing short-term fluctuations.
Certain Energy plans to use its Series A round to move its manganese-based storage system towards commercial deployment while demonstrating the technology at grid-connected scale.
Concretely, the new capital is set to support the development of a grid-connected MWh-class system in India, expansion of Certain Energy’s research facilities in the UK, and the establishment of a supply chain capable of supporting further commercial projects.
Source: EU-Startups
