Assessment of the feasibility of hydrogen storage in salt caverns: Implications for purity and contamination pathways for fuel cell mobility

Salt caverns are increasingly considered for large-scale hydrogen storage to support Germany's energy transition and decarbonization goals. This study investigates the feasibility of hydrogen storage in a small salt cavern in Rüdersdorf, Germany, focusing on hydrogen purity after underground storage. Using controlled injection and withdrawal experiments, hydrogen samples were analyzed for contaminants according to EN 17124:2022. The results demonstrate that the hydrogen purity remained high (>99.95 %) after storage, however, nitrogen (up to 450.07 μmol/mol), water (up to 67.95 μmol/mol), and halogenated compounds (up to 0.159 μmol/mol) exceeded the standard's thresholds. Nitrogen contamination is linked to the initial use of a nitrogen blanket during cavern construction and diminished after subsequent injections. Persistent water and halogenated compound concentrations indicate the need for limited purification steps to meet fuel cell mobility requirements. This study provides crucial empirical data on contaminant behavior in salt cavern hydrogen storage, advancing understanding for future large-sale applications. • Salt cavern H 2 storage for fuel cell mobility is feasible with minor purification. • Overall purity of H 2 was above 99.950 % after cavern storage. • Using a N 2 blanket for brining does not cause permanent contamination of stored H 2 . • Constant contamination of H 2 with moisture highlights need for drying steps.