Low-cost industrial feedstocks derived calcium-based pellets assisted by pores regeneration for direct solar-driven thermochemical energy storage

Calcium-based thermochemical energy storage (TCES) offers unique advantages of high energy density, long-duration energy retention, and high operation temperature, making it ideally suited for next-generation concentrated solar power (CSP) plants. However, the inherently poor cyclic stability and solar absorptance of CaO/CaCO₃ limit its commercial viability. Conventional strategy relies on incorporating expensive inert supports and absorption enhancers into Ca-based materials, yet inevitably amplifies production costs. Here, low-cost industrial feedstocks derived Ca-based pellets assisted by pores regeneration are proposed for direct solar-driven thermochemical energy storage. Aluminous cement and manganese sand are used as the inert support and absorption enhancer additive, respectively, serving as cost-effective alternatives to expensive reagents. Composite Ca-based pellets possess a high energy storage density of 953 kJ/kg over 50 calcination/carbonation cycles, which is 2.09 times higher compared with conventional limestones. Direct solar thermochemical energy storage power density achieves as high as 1.68 kW/kg, which is enhanced by 30.2%. The underlying mechanism is attributed to pores regeneration during calcination-carbonation cycles, which are created by differential deformations of active CaO/CaCO₃ and thermal pretreated enhanced inert skeletons. Furthermore, it achieves an industry-leading energy storage economy of 4.63 MJ/$, highlighting distinct low-cost advantages compared with similar energy storage materials reported in the literature. This work proposes a cost-effective strategy for engineering Ca-based TCES pellets, bridging the gap between high-performance thermochemical energy storage and scalable industrial applications.