Controllable preparation method and thermal properties of composite phase change materials based on starch pore formation

The lack of mass-producible, high-performance medium-high temperature phase change materials (PCMs) is one of the core problems restricting the efficient utilization and application of renewable energy. In this paper, a new type of composite phase change materials (CPCMs) based on starch pore-forming porous SiC ceramic skeleton combined with high enthalpy ternary chloride (NaCl–KCl–MgCl2) is proposed. The preparation process of CPCMs is optimized, and many characterization and experimental studies are carried out. The SiC skeleton with adjustable porosity (48%–75%) and robust structure is obtained by simple starch pore-forming, cold pressing, and high-temperature sintering. After 200 repeated charging-discharging cycles, the structure of the SiC skeleton/paraffin composite (porosity: 60%; thermal conductivity: 19.72 W m−1 K−1) is intact, with no obvious leakage and only a 3.06% decrease in thermal conductivity, which proves its excellent cycle thermal stability. The thermal conductivity of the CPCMs-60% impregnated with ternary chloride under negative pressure is 22.65 W m−1 K−1, and the effective heat storage density is 513.462 kJ kg−1 in the temperature range of 300–500 °C. In addition, a large number of cylindrical CPCMs batteries are fabricated by this process, and a series of systematic experimental studies are carried out in the laboratory. The temperature changes throughout the charge-discharge process and the effects of the flow rates of different heat transfer fluids on the thermal performance of the system are studied in detail. All of them verified the high charge-discharge rate and thermal performance of CPCMs batteries. This work provides a promising strategy for the development and industrial application of high-temperature packed bed heat storage systems for renewable energy integration.