Studies on Metal Hydride Based Hydrogen Storage and Purification Systems

Abstract

The world is witnessing an inevitable shift of energy dependency from fossil fuels to cleaner energy sources like wind, solar, hydrogen, etc. The governments from all over the world have realized that for limiting the global rise in temperature to 1.5 °C, hydrogen has to be given a reasonable/sizable share in meeting global energy demand by mid of 20th century. Hydrogen can be produced through several means using renewable energy sources and can be stored either in solid, liquid or gaseous state. Though, compressed and liquefied hydrogen storages are well-established technologies in the commercial sector, however, due to the leakage risk, boil-off losses and explosive nature, world is exploring a safer way of hydrogen storage i.e. absorption/adsorption based solid-state hydrogen storage technology. Although hydrogen can be produced from various extraction processes, such as through decomposition of fossil fuels, electrolysis of water, thermolysis of water, biomass conversion, etc., it is not always in the pure form. Metal hydride (MH)- hydrogen system can be a suitable solution for safe hydrogen storage and easy purification technology. Considering these issues, in the present study, thermodynamic screening of MH alloys was studied to filter suitable alloys for efficient working of metal hydride based hydrogen purification system MHHPS. From alloy screening, LaNi4.7Al0.3, LaNi5 and La0.9Ce0.1Ni5 alloys were considered for MHHPS. In order to check feasibility of metal hydride (MH) for hydrogen storage and purification application, parametric investigation of LaNi4.7Al0.3, LaNi5 and La0.9Ce0.1Ni5 alloys have been performed by varying different set of experimental parameters like hydrogen supply pressure, absorption temperature, and desorption temperature at fixed flow rate of ‘heat transfer fluid (HTF)’ at 4 lpm. The experiments have been carried out using 6 ECT reactor configuration. The rector was designed using numerical simulations performed using COMSOL Multiphysics, and further the numerical results were validated using experimental data. The results show that, all the selected alloys were suitable for hydrogen storage and purification application. Parametric studies for optimizing the operational parameters of the coupled reactor in multi-stage MHHPS were performed. For efficient system operation, the suggested absorption temperature is in the range of 20 °C to 30 °C with supply pressure 5 bar to 20 bar, while the flushing and desorption are suggested in the ranges of 15 °C to 20 °C and 70 °C to 90 °C, respectively.