The role of storage systems in hydrogen economy: A review

An economy based on hydrogen is widely regarded as the potential successor of the fossil-fuel-driven present energy sector. One major obstacle in developing the hydrogen economy is the suitable storage systems for different applications. This article presents an overview of the role of different storage technologies in successfully developing the hydrogen economy. It reviews the present state of various hydrogen storage systems from the surface and underground storage methods, their applications, and the associated scientific challenges. The integration of renewable energy in existing energy infrastructure requires developing suitable storage solutions along the energy supply chain. Large-scale seasonal hydrogen storage can be achieved through a subsurface geologic medium such as salt caverns, depleted hydrocarbon reservoirs, aquifers and hard rock caverns. The suitability of the geostructures depends on the desired storage cycles, capacities, and purity of stored hydrogen. The storage of hydrogen for stationary and mobile applications according to end user demands, generally less in capacity and requiring rapid storage cycles, is facilitated by surface storage methods. The physical storage of hydrogen is trapping it in vessels in its different physical states, such as compressed gaseous, cryogenic and cryo-compressed forms. Material-based storage of hydrogen is by adsorbing or absorbing hydrogen using solid-state materials. The performance of surface storage technics is characterized by gravimetric and volumetric densities, storage uptake and release kinetics, the cost involved, and operational safety. The technical insights of each storage technology are presented with recommendations and relevant fields of applications. No storage technic in its ideal conditions can be considered the best fit for all the applications, and each technic requires intense work to become acceptable for energy application.