Integrated Geological Hydrogen Storage in Depleted Gas Reservoirs: A Techno-Economic Assessment

Abstract Hydrogen storage is essential for the global transition to clean and sustainable energy, as it can balance variable renewable power, improve energy security, and support a reliable hydrogen supply. Among large-scale storage options, underground hydrogen storage in depleted gas reservoirs is a promising solution due to its high capacity and the potential to leverage existing infrastructure. In this study, an integrated subsurface–surface techno-economic framework was developed for the Dawn Hub depleted gas reservoir in Ontario, Canada. The framework models hydrogen blending with natural gas at the surface, reservoir injection and withdrawal, pressure swing adsorption (PSA)-based hydrogen separation, and recompression for delivery. A two-zone reservoir model, representing working gas and cushion gas with interzone mixing, was used to capture cyclic storage behavior and its effect on hydrogen recovery and gas composition. The subsurface and surface models were validated using field, industrial, and literature data, providing a reliable basis for cost assessment. Three infrastructure cases were studied: Scenario 1, injection, separation, and recompression only; Scenario 2, Scenario 1 plus hydrogen transport; and Scenario 3, Scenario 2 plus natural gas transport. The total levelized cost of hydrogen (LCOH) decreased with plant scale, with Scenario 1 and Scenario 2 approaching ∼9 USD/kg H2 at large scale, while Scenario 3 remained higher at ∼12–13 USD/kg H2. The lowest median LCOH was obtained at 15–20 mol % H2 injection, reaching ∼9.67–9.68 USD/kg H2 in Scenario 1. When the hydrogen feedstock cost was excluded, the cost trend became more clearly decreasing with increasing H2 concentration, and the facility-driven LCOH dropped from about 2.1 to 0.45 USD/kg H2 in Scenario 1, 3.1 to 0.66 USD/kg H2 in Scenario 2, and 14.5 to 1.4 USD/kg H2 in Scenario 3 between 5 and 50 mol % H2. Overall, the framework provides a practical basis for generating cost curves and supporting design and operational decisions for underground hydrogen storage in depleted gas reservoirs.