Experimental investigation of high performance composite phase change materials based on sodium acetate trihydrate for solar thermal energy storage

Latent thermal energy storage is a novel technology based on phase change materials (PCMs) for storing and transporting energy. Sodium acetate trihydrate (SAT) has a large latent heat, but its application is severely restricted by supercooling and phase separation. In this study, a high-performance composite PCM (SAT/SiC/EG) containing SAT (as the PCM matrix), silicon carbide nanoparticles (SiC; as a nucleating agent), and expanded graphite (EG; as a supporting material) were synthesized by stirring and ultrasonic dispersion to ameliorate supercooling and phase separation. The maximum supercooling degree of the composite PCM with 2 wt% SiC and 2 wt% EG was 1.1 °C after 200 heat storage and release cycles. Interestingly, the introduction of EG significantly inhibited the phase separation of SAT, and the composite PCM exhibited excellent dispersion stability after 200 cycles. The addition of 2 wt% and 3 wt% EG significantly improved the thermal conductivity of the composite PCM by 1.09- and 1.77-fold, respectively, as compared to that of SAT. Additionally, the prepared composite PCMs exhibited a large latent heat capacity and a good thermal cycling performance, where the melting and freezing enthalpies of SAT/SiC/EG containing 96 wt% SAT, 2 wt% SiC, and 2 wt% EG was 252.1 J/g and 222.1 J/g, respectively. This study demonstrates that the SAT/SiC/EG composite PCMs have extensive application prospects in middle-low temperature solar thermal energy storage. © 2021 Elsevier B.V.