Preparation And Application Of Phase Change Materials In Energy-Saving Buildings

Phase change material is able to store thermal energy and release heat promptly, and is therefore contributing to solving the unbalance of energy supply and demand with time and space. In this sense, it may achieve the goals of reducing energy consumption and improving energy efficiency. Phase change materials are currently considered to be suitable for application to the building envelope, through which it could absorb and store heat that enter the room during the day and release it at night to keep the room temperature in a comfortable range thereby lowering heating and cooling energy consumptions of the building.In this paper, a critical review of literature concerning PCMs is presented at first. Melting point and latent heat of PCMs are inherent properties of a material and determined by their molecular or atomic structures, and therefore the key factors associated with the melting point and latent heat of PCMs referring to the crystal chemical bond theory is discussed.According to the selection principle of PCMs, biodiesel byproduct-glycerol, a cheaper resource with low temperature phase change temperature is used. For better performance of PCMs, the mixture of glycerol and 1, 6-hexandiol is recommended. Key performances, including phase change temperature, super-cooling degree, transition heat and thermal stability of PCMs are investigated in experimental apparatus. Referring to phase change temperature, the mixtures are obtained, whose temperatures are between 21 to 28℃.The latent heat of mixtures is smaller than that of the average of polyol. The mixture of latent heat is about 76.4% of the polyol. The maximum deviations of the freezing point and the latent heat of the mixture are 4.6% and 7.8%, respectively, through 100 times cooling and heating cycles.Solid-liquid phase change materials are usually subject to fluidity limit, physical method to absorb PCMs to activated carbon materials is therefore investigated. Through DSC, SEM, TG testing, results show that the 40% content of mixed alcohol is the most appropriate in the form-stable phase change materials.