Collaborative Design of Light-Absorbing Shell Wrapping and Inner Thermal Conductivity Enhancing for Ca-Based Thermochemical Heat Storage Pellets

The light-absorbing shell-wrapped Ca-based TCES (thermochemical energy storage) pellets are well-suited for volumetric receivers employed in solar-driven CaL (Calcium-Looping) systems. However, shell shedding coupled with the low intrinsic thermal conductivity of the internal core restricts these Ca-based TCES pellets' practicality. In this work, high-temperature Fe-welding is employed to consolidate the light-absorbing shell, while SiC is doped into the interior core to enhance its thermal conductivity. The generation of CaFe 2 O 4 (a readily sinterable phase) from the bimetallic Fe/Mn light-absorbing shell is observed, with this phase serving as a key mediator that reinforces the core-shell interface and thereby suppresses shell shedding efficiently. Doping 4 wt% SiC into the Ca-based interior core facilitates its rapid heating to 1255.8 K in 30 s under concentrated radiation. In contrast, undoped, shell-free pellets only achieve 723.8 K after 70 s, a temperature inadequate for initiating CaCO 3 decomposition under identical flux conditions. Therefore, the innovative design of the Fe/Mn bimetallic shell integrated with a 4 wt% SiC-doped Ca-based core produces a durable TCES pellet. This pellet retains a thermal storage density of 1.03 MJ kg −1 after 29 cycles and achieves an average solar absorptance of 85.29%, thereby qualifying it as a promising candidate for solar-driven CaL systems.