Decomposition kinetics of Al- and Fe-doped calcium carbonate particles with improved solar absorbance and cycle stability

Calcium-based materials are considered to be promising heat storage methods for the upcoming 3rd generation concentrated solar power systems (CSP) due to their high operation temperatures and energy storage densities. However, pure calcium carbonate (CaCO3) particles suffer from poor solar absorptance and stability. In this work, we successfully enhance solar absorptance, cycle stability, and decrease decomposition temperature, simultaneously, based on proposed doped CaCO3 particles. A fabrication method, which is cheap and suitable for large scale applications, is proposed based on doping Al and Fe elements into CaCO3 powders via sol-gel processes. The average solar absorptance is enhanced by about 560%, and the energy storage density decay rate after 50 cycles is prominently reduced to be as low as 4.5% from 35.5%. The decomposition temperature is reduced by 15 to 24 K depending on the atmospheres, and the decomposition kinetics of both doped and pure CaCO3 particles is found to follow the equation of phase boundary controlled reaction. The activation energy increases only slightly after doping, but will have a sharp increase when switching the atmosphere from N-2 to pure CO2. This work paves the way to the design of high-performance calcium-based materials for next -generation high temperature thermal energy storage system.