Led by Storengy (part of the Engie Group), the ‘Hypster’ project has confirmed the feasibility of storing hydrogen in salt caverns. This milestone paves the way for large-scale deployment to accelerate the decarbonisation of industry and heavy transport, as well as support electricity production.
Launched at the end of 2024, tests on the Hypster system (Hydrogen Pilot STorage for large Ecosystem Replication) were carried out over a four-month period at the Étrez site in the Ain department. According to an AFP release, the results validated “the potential for the commercial use of hydrogen storage in salt caverns.” “The aim of the demonstration was to observe how salt interacts with hydrogen,” explained Mylène Poitou, Deputy Director of Industrial Projects at Storengy.
The testing involved injecting three tonnes of hydrogen into a cavern located 800 metres underground. In total, over 100 injection and withdrawal cycles were successfully completed.
A Storage Method Endorsed by France’s National Strategy
The announcement comes as France updates its national hydrogen strategy, with large-scale storage identified as a key element. The revised strategy notes that the flexibility of electrolysis “will require” medium-term storage in salt caverns, in addition to short-term surface storage solutions located near production and consumption sites.
A joint study published in summer 2023 by RTE and Natran (formerly GRTgaz), and echoed in RTE’s 2023 forecast report, highlighted the economic value of developing initial storage capacities and connecting them to regional hydrogen hubs.
“Engie is advocating for a clearer regulatory framework for hydrogen storage,” says Charlotte Roule, Vice President for Hydrogen at Engie and Managing Director of Storengy.
France’s first hydrogen storage facility in salt caverns — and the fifth in Europe — features 20 operational caverns located between 1,300 and 1,600 metres deep. The most recent of these is capable of storing the equivalent volume of 10 Arc de Triomphe monuments. The main potential sites identified for expansion are near the industrial hubs of Fos-sur-Mer and the Vallée de la Chimie.
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