Question to the Department for Energy Security & Net Zero:

To ask the Secretary of State for Energy Security and Net Zero, pursuant to the Answer of 19 October 2026 to Question 31002 on Thermal Energy Storage, for what reason the eligibility criteria for the Ultra-Long Duration Energy Storage Challenge is restricted to electrochemical technologies.

The Ultra-Long Duration Energy Storage Challenge is a research and innovation competition run by UK Research and Innovation (UKRI) and is part of the £102 million Clean Energy Challenges suite under the R&D Missions Accelerator Programme. The programme is being delivered in phases. The first phase covered electrochemical storage and the second phase supports the development and testing of systems which store hydrogen underground. Depending on budget and future net-zero need, there may be future phases covering other forms of energy storage.