Experimental analysis on a Power-to-Hydrogen system based on PEM electrolysis and metal hydrides: Empirical correlations for optimal system design and performance improvement

Metal Hydrides (MH) represent a promising technology for hydrogen storage, traditionally characterized using Pressure-Composition-Temperature (PCT) diagrams. However, real-world applications introduce additional complexities, such as non-equilibrium conditions driven by fluctuating hydrogen production rates and the chemical kinetics of MH materials. These factors necessitate dynamic response studies to optimize storage strategies, particularly in the context of renewable energy integration. This study investigates a Power-to-Hydrogen (P2H) system coupling a 2.5 kW Proton Exchange Membrane (PEM) electrolyzer with AB2-type MH canisters (190 NL or 800 NL), a configuration that remains underexplored in current literature but aligns with practical application scenarios. The experimental campaign focuses on key aspects: the influence of MH storage size, the impact of thermal conditioning on storage performance, and the operational dynamics of the hydrogen generator, with particular attention to hydrogen venting and current ripple phenomena. Results show that the 800 NL canister allows a better coupling with the considered electrolyzer (119 g of stored hydrogen corresponding to 6.35 kWh of stack consumption in the best case) and a mean stack efficiency of 61.4 % can be achieved with thermal conditioning (water cooling to maintain 20 °C during the adsorption phase). Overall, the findings provide critical insights into optimizing the PEM electrolyzer-MH tank interaction under real-world conditions, offering guidance for improving hydrogen storage system efficiency. This work contributes to advancing hydrogen-based energy storage systems, enhancing their role in supporting renewable power integration and promoting energy sustainability.