UK Government launches £28m challenge for 100-hour energy storage

The UK Government has launched a £28 million programme to develop ultra-long-duration energy storage technologies capable of supplying electricity for at least 100 continuous hours.

The Ultra-Long Duration Energy Storage Challenge covers new electrochemical technologies alongside the development and testing of underground hydrogen storage.

Its first electrochemical funding round is already under way. Innovate UK opened a £3 million competition for project-development studies on August 3, ahead of the wider challenge being formally launched on August 20.

At least £10 million has been allocated for a planned second phase supporting large-scale demonstrators, which is expected to open in mid-2027.

The competition is testing more than just technical performance, however. After all, there are many technologies that technically work, but then are unviable in numerous ways – whether it’s technologies that are difficult to scale or cost prohibitive. That’s why applicants must show a credible route from storage technology to a project that can be consented, connected, financed, constructed and operated in the UK.

From technology to grid-connected asset

The electrochemical programme is split into two streams reflecting different levels of technology maturity.

Near-commercial projects must plan for a grid-connected demonstration of at least 100 MWh by 2030. The technologies are intended to store energy over several days, with potential applications including energy arbitrage, uninterruptible power supplies and backup power during long outages.

A second stream targets earlier-stage technologies intended for longer-term applications, including monthly or seasonal storage and strategic reserve. These projects need a route to a grid-connected pilot of at least 100 kWh by 2030.

Technologies in both streams must provide at least 100 continuous hours of discharge availability and achieve a working life of at least 25 years.

The development studies must identify a specific site and include engineering design, while applicants are expected to address planning, grid integration, commercial viability and supply-chain delivery. The deployment plan for a future demonstrator must also account for a suitable grid connection or formal connection offer, alongside financing and customer arrangements.

That puts the programme well beyond laboratory-scale research, which is specifically excluded from the competition.

It also sets a much longer storage requirement than the UK's existing long-duration electricity storage regime. Ofgem's cap-and-floor scheme requires eligible projects to discharge continuously at full power for at least eight hours. The mechanism was introduced to support investment in long-duration electricity storage by providing greater revenue certainty for developers.

Ofgem is separately progressing its first cap-and-floor window, with its minded-to position covering 16 projects representing 7.6GW and 137GWh of storage capacity. That forms part of a wider shift towards turning the UK's growing flexibility pipeline into operational assets, highlighted in the Government's latest Clean Flexibility Roadmap update.

The Ultra-LDES challenge is aimed further along the duration curve, at electrochemical technologies that have yet to be commercialised at scale.

Hydrogen storage could also be boosted

The second part of the £28 million challenge will support the development and testing of underground hydrogen storage systems.

The Government says large-scale hydrogen storage could provide another way of storing renewable energy over an extended period and has estimated that it could reduce total energy-system costs by between £14 billion and £50 billion from 2035 to 2050.

Applications for the first electrochemical phase close on September 30, ahead of the planned demonstrator competition in mid-2027.