Comparative analysis of the efficiencies of hydrogen storage systems utilising solid state H storage materials

Highlights: • Performance evaluation of H stores with various solid H storage materials was done. • Volumetric and gravimetric H storage densities and energy consumption were evaluated. • Effects of H storage containment and heat exchanger were estimated. • Pressure–temperature conditions of H storage strongly affect the overall performance. • Material's packing density influences safety of operation and efficiency of H stores. - Abstract: Evaluation of the performances of hydrogen storage systems accommodating solid H storage materials should include characteristics on their reversible hydrogen storage capacity, operating pressures and temperatures, packing densities, and heat effects of hydrogen uptake and release. We have conducted a performance evaluation of the systems accumulating 5 kg of hydrogen in a containment of cylindrical geometry filled with a solid H storage material including such hydrides and reactive hydride composites as AlH₃, MgH₂, "low-temperature" (inter)metallic hydrides, NaAlH₄, Na₃AlH₆, LiBH₄ + MgH₂, and MOFs. The analysis yielded gravimetric and volumetric H storage capacities, and energy efficiencies of hydrogen stores. We conclude that the weight efficiency of hydrogen stores, apart from the gravimetric H storage capacity of the material, is greatly affected by its packing density, and by the pressure–temperature conditions which determine type and dimensions of the containment. The materials with low heat effects of H exchange, operating close to the ambient conditions, should be targeted in the course of the development of new hydrogen stores as offering the best energy efficiency of their operation