Development of novel numerical tooling for simulation of subsurface hydrogen and gas mixture storage

As the global climate crisis manifests through rising sea levels and temperatures, we reach a pivotal juncture in the effort to reduce anthropogenic carbon emissions. Hydrogen production and storage offer potential solutions to both the intermittency challenges of renewable energy systems and the need for sustainable alternatives to traditional gas infrastructure. Although we have extensive experience in operating natural gas storage in caverns, hydrogen storage does not benefit from this, having only been deployed for plastics and petrochemical industries. Although these applications have built a level of confidence for both professionals – and, perhaps more critically, the public – it leaves several avenues for exploration, as the operation varies vastly for energy storage purposes. These primarily revolve around how hydrogen storage within salt caverns may differ from natural gas (and compressed air) due to its thermophysical properties, and the impact of operational cycles on the adjacent rock. Addressing these gaps in knowledge requires the development and deployment of numerical tooling to provide valuable insight into the dynamics of hydrogen storage within salt caverns. This thesis addresses key concerns surrounding hydrogen storage in salt caverns through the development and implementation of numerical models. Specifically, the themes explored include: (i) modelling the effect of short-term storage cycles on cavern thermodynamic behaviour; (ii) extending numerical models to consider thermo-hydromechanical processes; (iii) accurate assessment of cavern operational constraints. In pursuit of these objectives, a novel gas storage modelling approach is validated, traditional gas storage is compared with hydrogen, a thermo-hydrodynamic model is extended to include mechanical deformation, and a structural analysis is conducted to identify operational constraints for hydrogen storage at a potential site. In summary, this thesis advances our understanding of hydrogen storage within salt caverns through the development of numerical tools and an investigation of the factors that will define effective and safe hydrogen storage.