Pioneering underground hydrogen storage: Insights from a first-of-its-kind field demonstrator in a depleted gas reservoir

Underground hydrogen storage (UHS) is a key enabler of the hydrogen economy, providing large-scale, long-term energy storage and supporting industrial decarbonization. Depleted porous reservoirs offer a promising option, although concerns about reservoir integrity, hydrogen-rock or -fluid reactions, and microbial activity have delayed deployment. Over a decade, extensive studies and field tests have addressed these challenges. The consistently positive results enabled RAG Austria AG to develop the first demonstrator-scale pure hydrogen storage facility in a depleted gas reservoir integrated into the local energy network. This article presents results from two successful storage cycles achieving 450,000 Nm 3 of stored hydrogen and recovered purity above 98 vol% prior to conditioning. H 2 S remained below detection limit, indicating negligible souring. Reservoir surveillance showed behaviour comparable to natural gas storage, confirming technical feasibility and safety. These findings reduce technical barriers, increase the Technical Readiness Level (TRL), and support UHS as a cornerstone of future energy systems.