Development of pomegranate-type CaCl2@C composites via a scalable one-pot pyrolysis strategy for solar-driven thermochemical heat storage

[Display omitted] •A facile one-pot pyrolysis strategy was proposed to prepare the CaCl2@C sorbent.•The solar-driven thermochemical energy storage can be achieved in the sorbent.•The energy storage density of Ca/CT200-700 was 254 kWh/m3 in a storage cycle. This study aimed to develop a novel sorbent for solar driven thermochemical heat storage. The core-shell CaCl2@C composites with tunable CaCl2 loading were obtained by a facile one-pot pyrolysis strategy, with the low-cost and abundant coal tar being used as the carbon precursor. CaCl2 was confined to the mesopores and macropores of the carbon shell, which led to a better structural stability than that of the impregnated sorbent. Moreover, the light-to-heat conversion of carbon shell was followed by the thermal energy storage by calcium chloride. In addition, the surface temperature of Ca/CT200-700 under the simulated sunlight of 1000 W/m2 increased to 75 °C. After irradiation for 230 min, the volumetric energy storage density of Ca/CT200-700 was 254 kWh/m3, with the water loss of 0.81 g-H2O/g-sorbent. This core–shell sorbent will provide new insights into the field of solar thermal conversion and storage.