Shape-Stable, Phase Change Composite Hydrogel for Solar Thermal Energy Storage and Electrothermal Conversion

Phase change materials (PCMs) are crucial in energy storage. However, they often suffer from high rigidity, poor thermal conductivity, and weak light absorption capabilities. In this study, a phase change hydrogel was developed by incorporating a hydrated salt, polymers, and carbon nanotubes (CNTs). The energy storage material used was disodium hydrogen phosphate dodecahydrate (DHPD), with sodium polyacrylate (PAAS) formed through thermally initiated in situ polymerization and starch (ST) serving as the flexible matrix. The results demonstrated that CNTs enhanced the composite’s thermal conductivity and light absorption ability. Under a simulated light intensity of 1000 W/m2, the light-thermal conversion efficiency of the composite reached up to 89.57%, and under a voltage of 10 V, the electric-thermal conversion efficiency reached a maximum of 81.85%. The enthalpy value reached 137.6 J/g, along with good thermal cycle stability. The proposed method not only overcomes the shortcomings in the development of traditional PCMs but also demonstrates its potential applications in solar thermal harvesting systems, flexible wearable thermal management devices, and electric-thermal energy conversion, effectively contributing to the advancement of sustainable development and energy management technologies.