Hydrogen Scotland member Gravitricity is a key part of the National Gas-led consortium, which Ofgem has recently awarded £500k to develop their novel underground hydrogen storage technology known as ‘H2FlexiStore’. The Gravitricity H2FlexiStore technology can be installed in a wide range of geological conditions, enabling large-scale hydrogen storage to be deployed in most necessary locations. This Ofgem funding could result in a pilot demonstrator hydrogen storage project being constructed in 2026.
How H2FlexiStore works:
H2FlexiStore has been developed by Gravitricity, energy storage specialists based in Edinburgh, and is designed to hold up to 100 tonnes of green hydrogen in purpose-built underground lined shafts. Their patented system utilises specially constructed geological shafts to store up to 100 tonnes of pressurised hydrogen at 200 bar per shaft, equivalent to 3.3 GWh of energy (lower heat value). The H2FlexiStore technology enables large quantities of hydrogen to be securely stored in close proximity to demand, for instance, as part of the National Gas network or adjacent to significant industrial users.
Gravitricity’s Co-Founder and Executive Chairman, Martin Wright, said: “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. “This support from Ofgem, enables us to prepare both technically and commercially for the delivery of a demonstration project next year and the early commercial projects within our existing pipeline of opportunities.”
The initial study concluded that underground nodal storage would compensate for the loss of ‘linepack’ (the amount of energy that can be stored in a pipe network) when transitioning to green hydrogen as a fuel. Strategically positioned nodal storage can enhance the resilience and operational efficiency of a hydrogen gas network, aiming to ensure security of supply for customers.
Next steps:
Once the design project is successfully completed, a third and final phase could be secured, resulting in the delivery of a technical demonstration project, bolstered by multi-million-pound funding from the Strategic Innovation Fund. A successful demonstrator project would validate the advantages of underground storage for the hydrogen industry and important infrastructure projects such as Project Union, which is exploring the potential to repurpose the existing gas grid for hydrogen, thereby creating a UK hydrogen backbone to connect production and storage assets with demand.
Although the UK has a limited number of underground salt caverns suitable for hydrogen storage, they exist only in very specific locations, which do not always align with where current or future storage demands will be situated.
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.”
The Ofgem funding will enable the consortium, which also includes Southern Gas Networks, Guidehouse, Edinburgh University, Energy Reform, and Premzero, to design and model a functional system over the next six months, in preparation for a potential demonstration phase next year. The funding is sourced from Ofgem’s Strategic Innovation Fund and follows the successful completion of a National Gas-led feasibility study in 2024, which identified H2FlexiStore as the preferred technology for providing locationally flexible hydrogen storage.
Martin Wright concluded: “By deploying H2FlexiStore, we anticipate network operators will be able to extend the life of existing assets as they transition to hydrogen by managing linepack swings more smoothly. In doing so, our technology improves the resilience of the network and overall energy security. This is of particular importance for a number of regions in the UK and particularly across Scotland, where there are no alternative or existing geological storage solutions.”
Wright added that in addition to its clear application in the UK, Gravitricity’s underground storage technology is likely to be deployed more widely in export markets as other countries seek to deploy their own hydrogen solutions.
Learn more here: https://gravitricity.com/h2flexistore/
