Experimental and numerical investigations on synergistic coupling of metal hydride hydrogen storage systems with low-temperature proton exchange membrane fuel-cell

Abstract

Hydrogen has emerged as a promising alternative for various energy needs, and metal hydride hydrogen systems offer significant potential due to their near-ambient working conditions and safe storage. This study presents experimental and numerical investigations on a lab-scale metal hydride fuel cell system to showcase its viability in addressing future energy demands. The experimental setup includes a 41-tube Metal Hydride (MH) reactor with an outer cooling jacket, containing 3.75 kg of La0.7Ce0.1Ca0.3Ni5. The output of the reactor is coupled to a 1 kW fuel cell, with controlled hydrogen discharge at temperatures ranging from 30 to 50 °C through numerical modelling. The study found that maintaining the reactor at 40 °C was sufficient to sustain the required bed pressure for a 1 kW fuel cell. Numerical simulations revealed that a 1 kW fuel cell operating at a current density of 0.8 A/cm2 and 50 °C rejected approximately 1.3 kW of waste heat. Moreover, 3.75 kg MH reactor could discharge hydrogen at a constant rate of 13 l/min for 36.3 min with just 125–225 W of heat input, highlighting the thermal coupling potential between these systems. The energy efficiency of the coupled MH-PEMFC system increased by 1.8 times to reach 49 % at 50 °C. Additionally, the waste heat generated proved sufficient to provide the required endothermic heat to multiple MH reactors, with a single reactor utilizing only 16.3 % of the total waste heat. This integrated system demonstrates promising efficiency and sustainability for future energy applications.