Investigation on performance and granulation of Nd-doped Li4SiO4 pellets for thermochemical energy storage

Abstract

Lithium orthosilicate (Li₄SiO₄) is well suited for energy storage systems in concentrated solar power (CSP) generation due to its large energy storage density, and relatively low regeneration temperature. However, performance degradation over multiple storage/release cycles is an urgent problem to be solved prior to its application. In this work, the transition metal Nd was employed as a promoter to modify Li₄SiO₄ heat carriers, and the results demonstrated that the Li₄SiO₄ heat carrier doped with 9 wt% Nd₂O₃ (LA-9Nd) had an energy storage density of up to 680 kJ/kg at 650 °C with almost no attenuation over 10 cycles, which was attributed to the lattice defects and inert frameworks formed by the Nd doping. The energy storage performance of LA-9Nd was also tested under harsh conditions, where high CO₂ concentration in the regeneration process deteriorated the carbonation performance of the heat carriers. In addition, to address the elutriation problem of Li₄SiO₄-based heat carrier powders during cyclic fluidization, water-graphite and agar-graphite granulation methods were used to granulate the LA-9Nd powders. The granulated pellets exhibited both good energy storage density and anti-attrition ability. In general, satisfactory energy storage density, cyclic stability and mechanical performance endow Nd-doped Li₄SiO₄ heat carrier pellets with great prospects for thermochemical energy storage.