Multifunctional response of biomass carbon/sodium sulfate decahydrate composite phase change materials

Building energy conservation has important practical significance for solving the energy crisis. Inorganic hydrated salt composite phase change materials (PCMs) with multi-functional responses provide new ideas for low-cost realization of building energy conservation. This paper selects corn stalks (CS) and corn cobs (CC), which have regular pore gaps, through-structure, wide distribution, and are economically recyclable, as raw materials to prepare biochar materials with rich pore structures through high-temperature carbonization. Modified sodium sulfate decahydrate (M-SSD) with excellent performance is organized by modifying borax and sodium carboxymethylcellulose. Then, CS, CC, and modified sodium sulfate decahydrate were used as raw materials, and a vacuum impregnation process was used to prepare biomass carbon-based composite PCMs. The results show that CS and CC have rich pore structures and are excellent adsorption carriers. M-SSD eliminates phase separation and reduces subcooling. The phase change temperature of the biomass carbon-based composite PCMs is 32.26 °C, and the phase change enthalpy is 188.9 J/g. It can complete heat storage and release at low voltage within the human body's safe voltage range and has good heat storage and release capabilities under simulated sunlight. Therefore, the ability of biomass carbon-based composite PCMs to store and release energy caused by excellent electrothermal and photothermal responses gives them great application potential in building temperature regulation.