Preparation and properties of composite phase change material based on solar heat storage system

Solar phase change hot water storage tank is a kind of storage / exothermic system with solar energy as heat source and phase change heat storage material. It can store heat during the day, continue to operate at night with stored heat without consuming other energy. Because of the poor thermal conductivity of solid-liquid phase heat storage materials, carbon fiber is added to enhance the thermal conductivity of phase change materials. Stearic acid is used as phase change material, carbon fiber as heat transfer material and ethyl cellulose as auxiliary material to prepare carbon fiber / stearic acid composite phase change material. Carbon fiber / stearic acid in the mass ratio of 7.5:92.5 is the optimal material and the chemical compatibility, phase change temperature, phase change latent heat, thermal conductivity and thermal stability of carbon fiber / stearic acid are measured by using SEM, XRD and DSC. From the DSC test, the latent heat capacity was determined as 192.6 J/g and the phase change temperature as 67.7°C. Thermal conductivity was measured as 0.4011 W/m⋅K. The storage / exothermic experimental system of carbon fiber / stearic acid composite phase change material is built. The melting process and solidification process of the composite phase change material are tested, and the storage / exothermic characteristics are analyzed. SEM and DSC analysis results revealed that the PCM had high thermal stability. XRD revealed that the binary eutectic mixture had good chemical stability. Thus, the new PCM possessed high latent heat with good thermal and chemical stabilities making it a potential phase change material for solar heat storage applications.