Salt cavern storage

Salt caverns are artificial cavities in underground salt formations created by the controlled dissolution of rock salt through the injection of water, which returns to the surface as brine and must be disposed of in an appropriate manner. Salt caverns are suitable for the storage of pure hydrogen due to the low cushion gas requirement (typically around 30% of capacity), the high sealing capacity of rock salt and the inert nature of the salt structures, which limits contamination of the stored hydrogen. The geographical availability of salt caverns is limited. Salt cavern storage is considered to be flexible and would allow several cycles of gas injection and withdrawal per year. Experience to date has shown that hydrogen can be effectively stored in salt caverns under low-frequency cyclic loading conditions. Ongoing research into hydrogen storage in salt caverns is aimed at demonstrating the feasibility of re-using caverns that have been used for natural gas and oil storage, particularly the risks of contamination and loss of stored hydrogen due to microbial activity.