Enhancing the heat transfer and photothermal conversion of salt hydrate phase change material for efficient solar energy utilization

Solar energy is intermittent, resulting in a discrepancy between the solar energy supply and building energy demand. Salt hydrate phase change material (PCM) is a promising material for use as an energy storage medium, but it suffers from a high supercooling degree, low thermal conductivity, and insufficient photothermal conversion efficiency. In this work, a novel sodium acetate trihydrate (SAT) composite was developed by synergistically using nano SiO2 (NS) as the nucleating agent, silicon carbide (SiC) foam as the thermal conductivity enhancer, and carbon nanotubes (CNT) as the photothermal enhancer. The supercooling degree of the modified SAT composite was only 1.4 °C, whereas the thermal conductivity and photothermal conversion efficiency could be increased to 1.54 W/(m•K) and 94.2 %, respectively. Most importantly, the payback period for applying the modified SAT composite in solar energy storage for domestic hot water supply is only 3.1 years, and the carbon dioxide emission could be reduced by approximately 1379.1 kg CO2-eq/year for a typical four-person family. Overall, the modified SAT composite with stable and excellent thermophysical properties offers great potential for the storage of solar thermal energy.