Design of high-performance and durable macrocapsules with ceramic-encapsulated aluminum for efficient solar energy absorption and storage

Phase change materials (PCMs), particularly metals, are widely employed for storing and releasing solar energy, aiming to address the fluctuations and intermittent nature of renewable energy sources. However, their implementation faces challenges such as limited spectral absorption, poor thermal storage capacity, and low wear resistance, which hinder broader application. This research introduces Al@SSBC microcapsule as a novel solution that combines photothermal absorption and energy storage functionalities. The design incorporates metallic aluminum encapsulated in a ceramic shell with superior spectral absorption. The ceramic layer captures solar energy, converting and storing it directly in the aluminum core, thus improving energy storage by eliminating extra heat transfer steps. Experimental evaluations reveal that the disk-shaped Al@SSBC-Wafer macrocapsule achieves an average absorption efficiency of 89.5 %, surpassing the traditional Al 2 O 3 shell by 63.9 times (absorbance 1.4 %). Notably, the macrocapsules exhibit excellent thermal stability, showing no leakage after 2000 operational cycles, a result of the self-sealing behavior of the aluminum core. At high temperatures, the aluminum forms a compact oxide layer, effectively shielding it from air exposure. Variants with higher aluminum content demonstrate enhanced thermal storage capacities, with the Al@SSBC-Sphere macrocapsule achieving a storage density of 797.0 J/g within a temperature range of 300–750 °C. Durability tests verify the Al@SSBC-Wafer macrocapsule's robustness, withstanding over 2000 cycles and crushing pressures above 99.4N. Furthermore, it experiences only a 0.07 % mass loss after a 60-h ball milling test. This study integrates photothermal absorption and storage in metal-based PCM macrocapsules, providing an innovative strategy for efficient high-temperature solar energy use.