Developed by Edinburgh energy storage specialist Gravitricity, the so-called H2FlexiStore system uses purpose built lined geological shafts to store up to 100 tonnes of pressurised hydrogen at 200 bar per shaft, equivalent to 3.3GWh of raw energy (enough to drive 10,000,000 miles in a hydrogen fuel cell car).
Although the UK does have a limited number of underground salt caverns suitable for hydrogen storage, they only exist in very specific locations, which don’t always match up with where current or future storage demands will be situated. Gravitricity claims that one of the key advantages of its system is that it can be sited in a wide range of geological conditions, and meet the requirement to safely and securely store large amounts of hydrogen close to demand.
The Ofgem funding follows on from a successful 2024 feasibility study which concluded that strategically located nodal storage can improve the resilience and operational efficiency of a hydrogen gas network. It will enable a consortium – which also includes Southern Gas Networks, Guidehouse, Edinburgh University, Energy Reform and Premtech – to design and model a working system over the next six months, ahead of a potential demonstration phase next year.
A successful demonstrator project would validate the benefits of underground storage to the hydrogen industry and key infrastructure projects such as Project Union, which is investigating the potential to repurpose the existing gas grid for hydrogen to create a UK hydrogen backbone to connect production and storage assets to demand.
Diagram showing storage capabilities of the H2FlexiStore system – Gravitricity
The Scottish Hydrogen Assessment’s ‘Green Export Scenario’ stated that Scotland could produce 3.3 million tonnes (Mt) of green hydrogen annually by 2045, with 2.5 Mt designated for export, and initial deliveries to mainland Europe expected before 2030. Gravitricity has separately completed commercial and technical feasibility work to confirm that H2FlexiStore can be deployed in this role.
Commenting on the announcement Kelvin Shillinglaw, Innovation Analyst at National Gas, said: “This project is a critical step forward in ensuring the UK’s gas networks are ready for a hydrogen-powered future. By embedding resilience with operational hydrogen storage directly into the transmission system, we can maintain operational flexibility, reduce costs for consumers, and support the decarbonisation of heat and power.”
Gravitricity Co-Founder and Executive Chairman, Martin Wright, added: “Given the strategic need for grid scale energy storage both nationally and internationally, it is crucial that enabling hydrogen storage technologies such as H2FlexiStore are commercially mature in time to offer cost effective resilience within current and future energy systems.
