Study of an autothermal-equilibrium metal hydride reactor by reaction heat recovery as hydrogen source for the application of fuel cell power system

This paper proposes a novel autothermal-equilibrium metal hydride reactor as the hydrogen source for the fuel cell power system, which employs phase change material (PCM) to recycle the hydrogen storage heat. A three-dimensional model of the metal hydride reactor coupled with a salt hydrate PCM for heat recovery is developed. Based on the model, the effects of key operating and design parameters on the reactor are investigated for performance optimization, including operating pressure, melting temperature, latent heat and thermal conductivity of PCM. Through the parametric analysis, it is found that increasing the operating pressure is beneficial to accelerate the absorption reaction. The average reaction fraction at 2400 s is increased by 24% with the pressure increasing from 6 to 10 bar. The moderate melting temperature and the thermal conductivity of the PCM that is comparable to that of metal hydride bed contribute to the improvement of hydrogen storage efficiency. Using this kind of hydrogen source reactor in a fuel cell power system, stable hydrogen storage efficiency of approximately 60% in the experiment is presented. In addition, no obvious performance deterioration of the power system occurs after ten cycles.