Compressed hydrogen is classically stored in steel overground tanks. Large underground storages of compressed hydrogen are extremely few whereas the challenge today is storing liquified hydrogen at very low temperature (cryogenic). Salt caverns are used for storing compressed hydrogen in gaseous state since the 1970s but suitable salt environments are limited and heterogeneously distributed, worldwide. Thus, storing compressed hydrogen in lined rock caverns (LRC) similar to compressed natural gas (CNG) is now envisaged. Currently there is only one example of LRC for storing CNG in operation and no compressed hydrogen rock cavern has been designed yet at an industrial scale. Regarding geomechanics, the conversion of salt caverns is relatively easy but more difficult for rock caverns, due to the required steel membrane and the quality of the host rock mass. The main design criteria and preliminary geomechanical modelling required for cavern creations and challenges for the conversion are also discussed.
In the context of the global warming and the need for green energy, the market requires an energy vector that can convey energy with a minimum emission of CO2. In this regard, hydrogen can be one of the vectors, if its production also can be made without CO2 emissions, such as electrolysis of water or membrane purification (Green Hydrogen). However, reforming of methane remains the majority production of (grey) hydrogen. The international demand of hydrogen will dramatically increase in the coming years and along with this demand, the storage of hydrogen shall develop (at the source, in hubs or close to the consumption centres). Various vectors can be used for hydrogen transportation and storage from pure hydrogen to more sophisticated and very promising forms such as ammonia or metal hydrated (Davoodabadi et al. 2021). This paper is limited to pure hydrogen and underground storage only.
