Enhancing Geological Storage of Hydrogen in Subsurface Caverns

Abstract Global hydrogen (H2) production is projected to reach ∼500 Mt/year by 2050. Large-scale storage of H2 is considered a pre-requisite for the hydrogen economy. Subsurface H2 storage including in salt caverns is seen as a viable option that supports large-scale storage and on-demand access to large-quantity energy. Here we present a novel methodology to use adsorbents in salt caverns for maximizing the amount of working gas that can be stored under a given geological scenario, with constrained pressure/temperature and H2 phase behavior. We evaluated the adsorption and desorption capabilities of various sorbent materials under different P-T conditions to determine most optimal sorbents for hydrogen storage. Scaled caverns filled with these sorbents will be subjected to representative P-T conditions in shallow caverns to investigate the hydrogen storage enhancement and also to quantify the potential impact of sorbents on cavern operations. Our results indicate that the microporous activated carbon material could be a suitable candidate for underground hydrogen storage. It demonstrates that under shallow cavern conditions, geological hydrogen storage capability can be potentially enhanced by up to 15% in sorbent-filled caverns when compared with traditional caverns without filling the sorbents. We evaluated multiple sorbent materials and noted that some of the commercially available porous sorbents could be used for this application with favorable economics over the lifetime of the cavern. We further suggest that our methodology can be potentially applied to the current operational storage sites, with the maximum enhancement for caverns with a shallower depth of < 600 m. Subsequent efforts will focus on optimizing and modifying the sorbents for improved commercial feasibility. Operational requirements place a strong constraint on the volume of working gas in a cavern. Maximizing the amount of working gas in each cavern could aid in reducing the operational footprint and associated costs by reducing the number of caverns needed for storage. Our results suggest that mechanical support from sorbents will also allow access to larger volumes of stored gas compared to caverns without sorbent. The proposed technology is at the intersection of novel chemistry and geological storage operations. It presents a novel way to significantly reduce the number of caverns needed while simultaneously reducing the operating costs over the life cycle of caverns.