Edinburgh-based underground energy storage business Gravitricity has signed a Memorandum of Understanding with infrastructure company VSL Systems UK to design lined rock shafts to store hydrogen.
They plan to build a scale demonstrator in the next 24 months, ahead of a nationwide commercial rollout.
Gravitricity believes that its FlexiStore technology is a ‘goldilocks’ solution to the future challenge of green hydrogen storage – offering a system that is larger and more secure than above ground hydrogen storage, and more flexible than subterranean salt caverns; the two most commonly-proposed alternatives.
Each rock shaft would be six metres in diameter, 365 metres deep and lined with steel. A single store would hold up to 100 tonnes of green hydrogen – sufficient to refuel more than 1,000 HGVS, or to power 500 buses for a week.
Gravitricity calculates that construction of around 1,000 FlexiStores would meet a quarter of the UK Government’s predicted 2050 hydrogen storage needs.
The stores can be constructed wherever required and are not dependent upon specific geological locations, meaning they can be built close to renewable-powered hydrogen production facilities where they can fuel industrial hubs and commercial hydrogen filling stations.
The company claims that a single FlexiStore could store the hydrogen generated by a 460 MW offshore wind farm and could be emptied and refilled daily, while multiple stores could soak up otherwise wasted or ‘constrained’ wind – which amounted to 3.6TWh in 2020.
Gravitricity and VSL are now seeking funds to build their first scale demonstrator project in the UK. The company is also in advanced discussions with Cumbrian steel firm Bendalls Engineering to fabricate the linings for the rock shafts.
“Green hydrogen will be a vital fuel of the future in industrial applications and in heavy transport, where electrification is just not feasible, or where industrial grey hydrogen is already used,” said Charlie Blair, managing director of Gravitricity.
“It is difficult to transport hydrogen, so it makes sense to locate hydrogen storage systems close to sources of renewable power - which can generate green hydrogen - and to potential users.“
VSL is part of the French Bouygues Construction group and is a contractor for the construction, preservation and repair of engineered structures and infrastructure.
Peter Hughes, managing director of VSL UK, said: “This project is fully aligned with the VSL vision to focus our engineering capabilities and solutions on the global transition to a low carbon future.”
The UK Government has highlighted a number of electrolytic hydrogen projects across the UK which will require hydrogen storage alongside renewable powered electrolysers.
Gravitricity has already identified a number of sites for the UK pilot project and is in discussion with site owners, including utilities, regarding the pilot project and future commercial schemes.
The business recently completed a £300,000 feasibility study, conducted with ARUP and funded by the UK Government’s BEIS HySupply programme, which showed it is technically and commercially feasible to store large amounts of compressed hydrogen in an underground lined rock shaft.
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