A review of underground hydrogen storage systems: Current status, modeling approaches, challenges, and future prospective

Our increased reliance on fossil fuels and its environmental effects have led us to prioritize transitioning to a carbon-free economy and using renewable sources of electric power. Hydrogen is an environmentally friendly, non-carbon-based energy source that can replace fossil fuels. It is critical to create a long-term storage medium to balance its intermittent supply and demand. Developing a full-scale H2 economy requires large-scale H2 storage. H2 storage in geological formations is being explored as a possible option where it can be withdrawn again at a larger stage for utilization. This study examines global underground operational and prospective locations to provide a comprehensive overview of the current state of hydrogen storage worldwide. Underground geological formations have effectively stored H2, as shown in the literature review. Geochemical, microbiological, hydrodynamic, and geomechanic factors affected by injected hydrogen are some of the key challenges in storing hydrogen in deep geological formations. These factors have a significant impact on the project's performance and operating efficiency. A roadmap for the implementation of underground hydrogen storage (UHS) is presented. The economic aspects of UHS were analyzed. Research is still ongoing on the potential effects of storing hydrogen in salt caverns, depleted oil and gas reservoirs, and saline aquifers, subsurface geological media. This study also encompasses the state-of-the-art hydrodynamic, geo-chemical and geo-mechanical modeling studies in the UHS domain, as well as several modeling software tools. Finally, conclusions, recommendations and further investigations were provided.