Abstract

In the global energy landscape, the diffusion of hydrogen - as a key energy vector for achieving decarbonization and sustainability objectives - could contribute to improving the safety of energy supply if associated with the development of affordable, large-scale and long-term storage solutions, including underground storage options. The underground storage of hydrogen represents, in fact, a potential solution to balance the inter-seasonal misalignments between the demand and supply of energy deriving from wind and solar plants, guaranteeing flexibility to the system, and using the existing infrastructures.

In this context, the need to promote research activities, aimed at evaluating the feasibility of the hydrogen geological storage process in potentially suitable sites arises, also supported by adequate modelling analyses, such as the one described in this paper.

The present study reports, in fact, the results of different numerical simulation scenarios carried out considering realistic geological model, under different operating conditions for the seasonal injection/extraction cycles of hydrogen-methane mixtures or pure hydrogen. In detail, two scenarios were simulated: depleted gas reservoir with injection of hydrogen-methane blend and saline aquifer with injection of pure hydrogen.

The numerical simulations were performed to verify the safety of caprock and reservoirs for the underground hydrogen storage process. The leakage of hydrogen represents the main risk for underground storage, so a proper evaluation of the properties and tightness of the reservoirs is a key factor, in a phase of feasibility study.

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