Reaction performance of CaCO3/CaO thermochemical energy storage with TiO2 dopant and experimental study in a fixed-bed reactor

The CaCO 3 /CaO reversible reaction pair is a promising thermochemical energy storage (TCES) technology for concentrating solar power (CSP) plants. However, the reaction performance and cyclic stability of this reaction pair is compromised because of sintering. In this study, TiO 2 -doped in CaCO 3 /CaO TCES system are systematically investigated by synchronous thermal analyzer (STA). The reaction kinetics of decarbonation process with and without TiO 2 doping are compared in N 2 and CO 2 atmospheres. Furthermore, the performance of CaCO 3 /CaO TCES system is analyzed in a fixed-bed reactor for future application. It is found that doping TiO 2 can improve the anti-sintering ability and cyclic stability of CaCO 3 , and the optimal doping ratio is 2.5 mol %, whose energy storage density is 1256.68 kJ/kg sample at first and improved by 2.26 times after 30 cycles. Moreover, doping TiO 2 decreases the activation energy and initial decarbonation temperature in CO 2 atmospheres. In exothermic experiments of fixed-bed reactor, the maximum exothermic temperature difference is 309.83 °C at 550 °C, and the highest absolute temperature reaches 848.7 °C at 750 °C. TiO 2 dopant promotes the decarbonation at lower temperature, and obtains a higher overall conversion (0.506) at 850 °C. Overall, CaCO 3 with TiO 2 dopant is of great significance for future industrial and commercial applications.