Modified Ca-Looping materials for directly capturing solar energy and high-temperature storage

The thermochemical energy storage based on Calcium looping (CaL) process shows great potential for the application in the 3^rd generation Concentrated Solar Power (CSP) compared to other high-Temperature heat storage schemes. However, due to the inherent low solar absorptance of CaCO₃, the surface heating mode is widely adopted in the conventional CaL-CSP system, which causes large thermal resistance and severe radiative heat loss. Herein, we propose achieving direct solar absorption in the CaL-CSP system through enhancing the CaCO₃’s ability to capture thermal energy from the concentrated solar irradiation. Efforts are devoted to design and fabricate a modified CaL material by doping CaCO₃ with some materials with high solar absorptance. In order to obtain a highly stable CaL, the cyclic performance of the composite material is investigated and optimized. The calcium gluconate ((Ca(C₆H₁₁O₇)₂)) was used as the precursor while fabricating the porous CaCO₃, and the Mn–Fe oxides were doped into CaCO₃ through two different doping processes. The experimental results indicate that the proposed material obtains the solar absorptance of ∼90%. The heat release efficiency (equal to carbonation activity) remains over 92% in 60 cycles, which is much higher than that of the commercial CaCO₃ powder (20% after 60 cycles). The proposed calcium-based thermochemical energy storage material is expected to dramatically improve both the solar utilization efficiency and cyclic stability of the integrated CaL-CSP system.