Multi-objective optimization of metal hydride hydrogen storage tank with phase change material

The use of hydrogen as a future energy source to supply world fuel is essential. The storage problem is one of the main challenges facing the use of hydrogen as a fuel. In this study, we model and optimize the transient operation of a 2D metal hydride storage tank. A phase change material (PCM) is attached to a metal hydride tank for heat recovery during hydrogen absorption and heat supply during desorption. Four parameters, porosity and diameter of the metal hydride tank, initial temperature and melting temperature of the PCM, are selected to optimize hydrogen absorption. An advanced optimization algorithm is applied to increase the hydrogen to metal ratio and decrease the absorption reaction time. The hydrogen to metal ratio and the absorption time, when system pressure equals equilibrium pressure, are considered as the two objective functions. The optimization and appropriate selection of design parameters result in a significant increase in the hydrogen to metal ratio. For better understanding, five particular points in the ranges of high, mediocre and low values of hydrogen to metal ratio are selected on the optimized Pareto front. The effects of the different parameters on the objective functions are discussed for the optimal points. A final (global) optimum point is obtained based on the LINMAP method that reasonably satisfies both objective functions and the results in this point are presented and discussed separately.