Green Hydrogen Storage in an Underground Cavern: A Case Study in Salt Diapir of Spain

The Poza de la Sal diapir is a closed circular depression with Cretaceous Mesozoic materials, formed by gypsum, Keuper clays, and a large extension of salt in the center with intercalations of ophite. The low seismic activity of the area, the reduced permeability and porosity of the salt caverns, and the proximity to the Páramo de Poza wind park, make it a suitable place for the construction of a facility for underground storage of green hydrogen obtained from surplus wind power. The design of a cavern for hydrogen storage at a depth of 1000 m takes into account the differences in stresses, temperatures, and confining pressures involved in the salt deformation process. During the 8 months of the injection phase, 23.0 GWh can be stored in the form of hydrogen obtained from the wind energy surplus, to be used later in the extraction phase. The injection and extraction ratio must be developed under the conditions of geomechanical safety of the cavity, so as to minimize the risks to the environment and people, by conditioning the gas pressure inside the cavity to remain within a given range.