Characterisation of La_0.9Ce_0.1Ni₅ alloy for the development of single‐stage thermally driven sorption hydrogen compressor

Abstract

Summary In this study, La0.9Ce0.1Ni5 alloy is characterised to investigate the performance of a single‐stage thermally driven sorption hydrogen compressor (TDSHC). The pressure‐concentration isotherm (PCI) properties of La0.9Ce0.1Ni5 alloy are measured through Sievert's Apparatus, and the thermodynamic properties are estimated by constructing van't Hoff plots at different temperature ranges between 20°C and 140°C. The effects of an increase in operating temperature on hydrogen storage capacity as well as on thermodynamic properties and the corresponding effects on TDSHC performance are studied. It is observed that the hydrogen storage capacity decreased, whereas reaction enthalpy increased, with an increase in operating temperature. It is also observed that the equilibrium pressure increased dramatically with an operating temperature; therefore, this alloy is employed, in this study, for the development of TDSHC. The proposed TDSHC operates at the supply temperature and pressure of 20°C and 15 bar, respectively, in which the compressed hydrogen is delivered at 40°C, 60°C, 80°C, 100°C, 120°C and 140°C with a maximum pressure output of 270 bar. The measured PCI and thermodynamic data are employed to investigate the thermodynamic performance of TDSHC which results in the maximum compressor work of 10.13 W and the maximum cycle efficiency of 27.57% with an average heat input of 35 ± 3 W. The increase in discharge temperature on system performance are observed to increase in compressor work and efficiency due to the increase in discharge pressure, whereas the effect on heat input is not significant due to the reduction in hydrogen discharge amount. Also, the behaviour of metal hydride (MH) bed is predicted through the finite volume method in terms of variations in MH bed temperature and hydrogen transmission. The numerical investigation is carried out by solving the required energy equations and are validated with experimental data. The numerical investigation results into minimum cycle time of 2700 seconds for the operation of TDSHC. It is also observed that the increase in discharge temperature increases the reaction kinetics and hydrogen mass fraction.