Innovate UK has opened a £3 million competition for project development studies intended to move electrochemical ultra-long-duration energy storage towards large-scale UK demonstration. The programme requires proposed systems to supply the electricity grid continuously for at least 100 hours and achieve a working life of at least 25 years.
Applications opened on 3 August and close at 11am on 30 September 2026. Individual projects can request between £350,000 and £700,000, must last between three and nine months, and are expected to begin by 1 January 2027 and finish by 30 September that year.
The immediate output is a development study, not a constructed storage asset. Each project must include a technology assessment, engineering design, cost and scale-up roadmap, market assessment, development plan, and manufacturing and supply chain plan.
That requirement places manufacturing and delivery alongside electrochemistry from the outset. A storage chemistry can perform well in laboratory testing and still prove unsuitable for commercial deployment if it depends on scarce materials, bespoke assembly, difficult maintenance, or processes that cannot hold acceptable tolerances at larger volumes.
The competition forms Phase 1 of a planned two-stage programme. Innovate UK has allocated at least £10 million for a second phase expected to open in mid-2027, supporting the development and delivery of large demonstrators.
Winning Phase 1 support will not be a condition of eligibility for the later competition. Developers can therefore enter Phase 2 independently, although the study programme gives applicants an opportunity to resolve practical questions before construction funding becomes available.
Those questions are substantial because 100-hour storage serves a different operating need from the lithium-ion systems now used widely for frequency response, short-duration balancing, and intraday trading. A system intended to discharge for more than four continuous days must retain enough stored energy to cover prolonged periods of low renewable output while remaining economical during long intervals when it may not be called.
The 25-year life requirement adds pressure to the engineering case. Developers will need evidence covering degradation, component replacement, maintenance access, safety, availability, and the cost of restoring lost capacity over decades. A technology that meets the discharge target but relies on frequent replacement of expensive cells, pumps, membranes, or power conversion equipment will move expenditure into operations rather than remove it.
Project proposals must support a planned UK demonstrator by 2030 and show that the lead organisation or consortium can progress from study work into deployment. That demands more than a technical model: applicants will need credible sites, connection assumptions, supply arrangements, construction plans, and a route through planning, permitting, finance, and commissioning.
Manufacturing readiness will be equally important. Proposals must identify the materials, equipment, workforce, suppliers, quality controls, and factory processes required to move from a prototype system to commercial output in the UK. The study should expose technologies whose cost estimates depend on manual production methods or component availability that will not survive increased demand.
Long-duration storage projects also face an awkward revenue problem. Their system value may be highest during infrequent periods of severe supply stress, but investors still require dependable income across ordinary years. Charging costs, wholesale prices, capacity arrangements, balancing services, and long-term contracts will influence whether an asset can support debt and equity on acceptable terms.
Round-trip efficiency cannot be considered in isolation. A lower-efficiency technology may remain competitive where its storage medium is cheap, durable, and easy to scale, while a more efficient design can fail if the installed cost or replacement burden is excessive. Developers will have to demonstrate the complete cost of delivered electricity across the intended operating life.
The programme is technology-neutral within defined electrochemical boundaries, allowing different approaches to compete against the same duration and lifetime requirements. Comparisons will be useful only where applicants use consistent assumptions for utilisation, degradation, financing, construction, and residual value rather than selecting whichever model presents their own technology most favourably.
The £3 million first phase is small beside the capital required for full-scale demonstration, but it is directed at the point where weak projects remain relatively cheap to stop. By the time Phase 2 opens, credible proposals should have moved beyond attractive chemistry claims and produced engineering layouts, costed manufacturing routes, delivery programmes, and identifiable project risks.
Innovate UK ultimately wants technologies that can be manufactured domestically and deployed at grid scale, rather than another collection of laboratory records. The studies will be useful where they narrow uncertainty before equipment is ordered; a thick report that leaves cost, factory capacity, and project delivery unresolved will merely delay the expensive questions.
