A comprehensive review of underground hydrogen storage: Insight into geological sites (mechanisms), economics, barriers, and future outlook

This investigation examines the underground storage of hydrogen in a variety of storage types, including caverns (salt and rock), depleted oil and natural gas reservoirs, and aquifers. It presents a roadmap for the execution of subsurface hydrogen storage. The cost-effectiveness of hydrogen production remains a significant determinant for its large-scale adoption. In its storage, a multitude of challenges and obstacles can arise and they are presented in this paper. It was observed that some characteristics of hydrogen must be sufficiently managed to ensure air tightness during its subsurface storage, migration, and withdrawal. The selection of geological formations for underground hydrogen storage should rely on a comprehensive geological assessment, including engineering factors. If there is any chance of hydrogen gas escaping from an underground storage facility beyond its defined boundaries, the location should be deemed unsafe and discarded. In addition, prior to the full-scale implementation of underground hydrogen storage (UHS), different obstacles in all aspects of regulations, geology, technology, and economics need to be tackled and resolved. Due to the intricate nature of the problem and the relatively limited expertise in this sort of operation, it is anticipated that an extended period of research will be necessary. Also, before any future implementations can occur, thorough investigations must be conducted to gain a deeper understanding of the mechanisms involved in hydrogen interaction with surrounding rocks and installations. Preparations should be made to mitigate all potential risks. These activities should be carried out within clearly specified time intervals.