Low-carbon shape-stable phase change composite utilizing semi-coke ash for building thermal energy storage

Abstract

To enhance the efficiency and cost-effectiveness of heating, air-conditioning, and solid waste recycling in buildings, this work proposed the solid waste semi-coke ash as skeleton material and the sodium carbonate as phase-change material to produce shape-stable phase-change composites using the cold compression-hot sintering method for building thermal energy storage. Eight shape-stable phase-change composites were prepared and the detailed chemical compatibility, thermal property, structural and mechanical performance, and micromorphology were investigated by X-ray diffraction, differential scanning calorimetry, laser flash analysis, N2 adsorption and desorption method, constant speed pressurization method, and scanning electron microscopy. Results demonstrated that semi-coke ash is suitable with sodium carbonate for fabricating shape-stable phase-change composites. The optimal mass ratio of semi-coke ash to Na2CO3 powder for sample CC3 was determined to be 52.5:47.5. This particular sample demonstrated a thermal energy storage density of 961.58 J/g and a maximum thermal conductivity of 1.306 W/(m ∙ K). It also exhibited excellent chemical compatibility between its components. Furthermore, sample CC3 displayed a mechanical strength of 23.57 MPa, with elements evenly distributed throughout. Importantly, CO2 emission from the production of sample CC3 was significantly low, indicating great potential for commercialization.