Optimising thermochemical energy storage: a comprehensive analysis of CaCO3 composites with CaSiO3, CaTiO3, and CaZrO3

Abstract

With the increasing amount of renewable energy produced, many governments and industries are pushing for the installation of battery energy storage system (BESS) solutions. Thermal batteries are systems that store heat made from various energy sources, and can be used to produce electricity upon demand. These systems are easily scalable and can be installed in cities, homes and remote locations. Thermochemical energy storage (TCES) uses the enthalpy of a chemical reaction to store and release heat through endothermic and exothermic processes, respectively. CaCO₃ has been identified as an ideal TCES material as it is cheap and abundant, but maximising long-term cyclability is key to ensure battery longevity. This article investigates the addition of CaSiO₃, CaTiO₃ and CaZrO₃ to CaCO₃ in a 1 : 1 ratio to ascertain the reaction properties and cyclic capacity over time. Cycling longevity and thermodynamic properties were determined using simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC–TGA) along with the Sieverts technique, and their reaction pathway studied by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The low cost of the CaCO₃–CaSiO₃ material of $1.8 USD per kW h_th suggests that if a suitable particle refinement agent were to be employed to ensure cycling longevity this material would be an excellent TCES material. Despite the CO₂ cycling capacity of the CaCO₃–CaZrO₃ system only reducing by 16 wt% over 100 cycles, the cost of ZrO₂ brings the materials cost to $30.9 USD per kW h_th, making this material currently unsuitable for application. The CaCO₃–CaTiO₃ system showed only a 17% drop in total CO₂ uptake over 100 cycles, although the cost was $11.1 USD per kW h_th.