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

Abstract 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.