A Critical Review on Parameters Affecting the Feasibility of Underground Hydrogen Storage

The need and demand for energy are ever increasing with the rapid urbanization of the global population. Near-future economic development and consequent expected industrialization are the strongest indicators of the rising energy requirement. Though fossil fuel and coal are catering toward a major chunk of energy demand, their negative or adverse impact in terms of emission of greenhouse gases (GHGs) and carbon dioxide (CO₂) is causing global warming and imbalance in environmental conditions, leading to a search for commercially viable alternate energy types. As renewable energies like solar and wind are weather-dependent, the search for an alternate energy supply needs to be done even more urgently. Hydrogen (H₂), being a carrier of alternate energy and not an energy source, can deliver or store a significant amount of energy. The stored energy can be utilized for the generation of power, electricity, and heat. Further, hydrogen is very pure in nature and therefore is widely useful from a flexibility and efficiency standpoint. It represents the predominant constituent within the natural environment, totaling about three-fourths of the universe. Storage of hydrogen has gained significance in recent times, and subsurface storage is being looked upon as a viable alternative. However, the successful storage of hydrogen in the subsurface is a function of critical parameters like wettability, capillary pressure, relative permeability, diffusion, microbial activities, etc., which themselves are dependent upon rock types with their corresponding mineralogical compositions, along with associated pressures and temperatures. This work critically reviews the impact that these parameters would have on the storability of hydrogen in the subsurface, evaluates the best possible solution, and recommends a future course of action through insights derived, which need to be considered while considering underground hydrogen storage.