Influence of effective thermal conductivity on hydrogen sorption in Mg-LaNi4.6Al0.4 composite hydride beds for thermal energy storage

Abstract

Thermochemical energy storage using metal hydrides is well known. Appreciable quantities of heat energy interactions involved in the hydrogenation and dehydrogenation processes of metal hydride make the metal hydrides suitable for the storage of thermal energy. This paper discusses the synthesis, Pressure Concentration Isotherm (PCI) characterization and estimation of thermal properties of Mg + 50 wt% LaNi4.6Al0.4 composite hydride suitable for thermal energy storage. Maximum theoretical energy density of 918 kJ/kg can be achieved in the temperature range of 150–200 °C. Low values (0.1–1 W/mK) of effective thermal conductivity (ETC) of metal hydride beds is responsible for poor heat and mass transfer characteristics of metal hydride beds. The ETC of Mg + 50 wt% LaNi4.6Al0.4 composite hydride bed was augmented by fabricating two types of pellets. The sorption kinetic measurements were performed for three different configurations of metal hydride beds, one with powder composite hydride and remaining with two different types of pellets. Enhancement in ETC improved the heat and mass transfer characteristics of the composite metal hydride bed.