Performance investigations on thermochemical energy storage system using cerium, aluminium, manganese, and tin-substituted LaNi5 hydrides

Abstract

The necessity to store solar thermal energy draws attention to the development of energy storage systems (ESS), which can be addressed by the implementation of metal hydride (MH) energy storage systems (MHESS). The successful operation of metal hydride energy storage systems depends on the properties of the metal hydrides employed, which vary with compositional changes. Therefore, in the present work, the influence of the substitution of Aluminium (Al), Manganese (Mn), and Tin (Sn) for Nickel (Ni) and Cerium (Ce) for Lanthanum (La) on LaNi₅ properties is studied in terms of hydrogen storage capacity (HSC), reaction enthalpy, working temperature, and pressure, and consequently on metal hydride energy storage system performance. The metal hydride properties were measured through the volumetric method using an in-house Sievert's Apparatus, and it was observed that the hydrogen storage capacity and equilibrium pressure are higher in the case of Cerium (1.48 wt%, 6.26 bar) substitution than those for Aluminum (1.43 wt%, 0.81 bar), Manganese (1.44 wt%, 0.9 bar), and Tin (1.4 wt%, 0.17 bar) at 20 °C. In contrast, the opposite trend was observed for reaction enthalpies. These metal hydride properties are applied to estimate the thermodynamic performance of metal hydride energy storage systems operating at 25 °C, 100 °C, 130 °C, and 150 °C using the metal hydride combination of La_0.9Ce_0.1Ni₅ – LaNi_4.7Al_0.3, LaNi_4.7Mn_0.3 – LaNi_4.7Sn_0.3 and La_0.9Ce_0.1Ni₅ – LaNi_4.7Sn_0.3. The coefficient of performance (COP) is observed to be 0.49, 0.46, and 0.54, respectively. Based on available driving pressure and thermodynamic performance, the combination of La_0.9Ce_0.1Ni₅ – LaNi_4.7Sn_0.3 is observed to be more suitable for metal hydride energy storage systems with energy storage of 2439.69 kJ for 10 kg of metal hydrides.