Large-Scale of Hydrogen Underground Storage in Salt Caverns: The Future of Sustainable Energy Storage

Hydrogen is taking a significant lead as a complementary energy carrier. One of the most significant structural challenges in the hydrogen supply chain is storing large volumes to ensure stability between generation, delivery, and utilization. In this context, geological storage in salt caverns stands out as the most promising technology. Salt caverns mined by leaching have unique physicochemical characteristics such as negligible permeability under high gas pressures (avoiding leakage), self-healing, higher levels of stability, and stress safety shield due to the creep phenomenon. Also, it allows higher injection and withdrawal ratios of Hydrogen, meeting cycles between demand and production, a minor need for cushion gas, and more controllable construction from the point of view of monitoring and tightness. At the end of the operational life of the storage system, the cushion gas can be extracted just by injecting brine into the cavern. This article presents a geomechanical case study of hydrogen storage in salt caverns in a speculative geological site within the boundary limits found in evaporite basins (Moriak 2008, 2012). It will also be presented the design of caverns in the same geological site to store natural gas with high content of CO₂. It will demonstrate the patented technology of gravitational separation of natural gas and CO₂ that occurs inside the salt caverns, as the density of the CO₂ is larger than the natural gas (Costa, 2018).