CaCO 3 is a promising material for thermochemical energy storage (TCES) systems. It can store and release heat upon reversible decarbonation to CaO, which emits heat through carbonation. Decarbonation temperature of CaCO 3 directly affects the properties of CaO, which influences heat supply in result. The current research studies CaCO 3 /CaO system, specifically analyzing the conversion of CaO into CaCO 3 (carbonation) for various CaO samples prepared at decarbonation temperatures between 600 and 975 °C. A relation is developed using regression analysis to verify the linearity between reactivity of CaO samples and decarbonation temperature at which it was prepared. The carbonation of all CaO samples at various partial pressures of CO 2 and temperatures is also analyzed. The whole process is performed for pure and SiO 2 doped systems (molar ratio 1:1). The efficient performance of CaCO 3 /CaO system is noted for decarbonation temperatures above 750 °C or below 925 °C for pure material. While for doped material, the decarbonation temperature for efficient performance lies between 700 °C and 800 °C. Both systems performed with higher efficiency when CO 2 pressure was kept constant and the carbonation temperature was increased.
CaCO 3 /CaO based thermochemical energy storage system has a promising potential for the concentrated solar power plants. However, the low reactivity and sintering of CaCO 3 /CaO restricts the energy storage/release performance of this system. In this work, we report ZnO as a new doping material for the CaCO 3 /CaO TCES system. We tested different loadings of ZnO and determined an optimal loading for the best performance. The reaction kinetics of both the doped as well as the undoped system in the decarbonation step is presented in detail. Furthermore, the energy storage capacity and the cyclic stability over first 100 cycles is reported. It is found that the ZnO-doped CaCO 3 can absorb 1478.8 J/g energy at the optimal loading. The cyclic conversion of the ZnO-doped system stabilizes after 20 cycles, which is an improvement from the undoped system that shows a slow but steady decline even after 100 cycles. ZnO seems to be a viable doping material, which considering its low cost and availability can lead to an improved thermochemical energy storage system.
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