Imperial College spinout Certain Energy has raised £10m to commercialise a manganese-based flow battery designed for long-duration electricity storage, with the British Business Bank investing £3.5m in the Series A round.
The financing gives Certain Energy, formerly RFC Power, additional capital to move its technology towards deployment as electricity grids seek economical ways to store renewable generation for periods measured in hours or days.
The funding round also includes Centrica Energy, Ceres Power, and Temasek Trust’s Catalytic Capital for Climate and Health.
Ceres is contributing £1m in cash alongside £1.5m of engineering services and expects to retain an interest of about 37% following the restructuring.
Certain Energy originated from research at Imperial College London and was established in 2017. Ceres acquired RFC Power’s remaining share capital and intellectual property in 2025 before the new financing and rebrand created a structure intended to support wider commercialisation.
The company is developing a hydrogen-manganese flow battery. Unlike conventional lithium-ion systems, flow batteries store active materials in tanks outside the principal electrochemical stack, allowing energy capacity and power output to be scaled more independently.
That architecture can be useful for longer-duration applications because increasing the amount of stored energy does not require the entire system to grow in the same way as a conventional battery pack.
Certain Energy is targeting grid-scale projects, renewable-energy installations, commercial and industrial customers, and off-grid applications.
The Series A will support development of a grid-connected megawatt-hour-class system in India, expansion of UK research facilities, and work to establish a supply chain capable of supporting repeat commercial projects.
Long-duration storage is gaining importance as wind and solar account for a larger share of electricity generation. Renewable output depends on weather rather than demand, creating periods of excess generation and other periods when flexible capacity is needed to cover shortfalls.
Lithium-ion batteries already provide rapid-response balancing and shorter-duration storage, but system economics become more challenging as discharge durations increase. That has encouraged investment in alternative technologies including flow batteries, compressed air, thermal systems, pumped hydro, and other chemical-storage approaches.
Commercial success depends on more than the underlying chemistry. Infrastructure customers need evidence covering round-trip efficiency, degradation, maintenance, availability, safety, installation time, operating life, raw-material exposure, and the cost of replacing components.
The ability to finance a project is equally important. Utilities and infrastructure investors need confidence that a system will continue performing for many years before they can assess revenue, warranties, and long-term returns.
Certain Energy argues that manganese offers advantages because it is relatively abundant and reduces exposure to some of the materials used in other battery technologies.
The next development stage will test whether those theoretical advantages survive at commercial scale. Energy hardware companies can demonstrate strong laboratory performance years before proving that systems can be manufactured, installed, and maintained repeatedly at a competitive cost.
A grid-connected project can close part of that evidence gap. Operating data provides prospective customers and investors with information on performance under real conditions and allows suppliers to understand the manufacturing tolerances and service requirements needed for repeated deployment.
Developing the supply chain will therefore be as important as expanding the research team. Flow batteries require tanks, pumps, membranes, electrochemical components, controls, power electronics, and other equipment to work as an integrated system.
The British Business Bank has been increasing its involvement in university spinouts and climate technology, particularly in areas where lengthy development cycles and capital requirements can make conventional venture investment harder to secure.
Energy hardware is a clear example. Building full-size systems requires significantly more capital than developing software, while customers often want commercial evidence before placing large orders.
The £10m round gives Certain Energy the resources to begin producing that evidence. It does not remove the scale-up risk: the company still needs to prove competitive economics, reliability, manufacturing repeatability, and access to customers.
If the Indian project performs as intended, the focus will increasingly shift from whether the chemistry works to whether Certain Energy can build a business and supply chain capable of delivering long-duration storage at infrastructure scale.
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