Structurally improved, TiO2-incorporated, CaO-based pellets for thermochemical energy storage in concentrated solar power plants

Abstract Calcium looping process (CaL) is a promising thermochemical energy storage technology for the application in the 3rd generation concentrated solar power plants (CSP). Hence, it is necessary to develop the highly efficient CaO-based heat storage composite materials. The structurally improved, CaO-based pellets were prepared via adding cellulose as the pore-forming template. Furthermore, the approach of TiO2 incorporation was adopted aiming to enhance the anti-sintering ability of the structurally improved, CaO-based pellets. It is found that the structurally improved, TiO2-incorporated, CaO-based pellets that containing 25 wt% of TiO2 exhibit the highest CaO carbonation conversion and energy density of 57.5% and 1827.7 kJ/kg after 20 cycles, which are nearly 1.3 times as high as those of the pure Ca(OH)2 pellets. The superiority of the structurally improved, TiO2-incorporated, CaO-based pellets on cyclic heat energy storage/release is more prominent under harsh calcination conditions (950 °C, pure CO2). The evenly distributed CaTiO3 grains, providing structural stability to the CaO-based pellets and also enhancing the anti-sintering ability, are responsible for the improved cyclic energy storage/release performance. Additionally, the desirable compression strength (16.67 ± 1.05 MPa) contributes to strengthen the practicability of structurally improved, TiO2-incorporated, CaO-based pellets applied in the CaL-CSP system.