Room-temperature flexible phase change material with high emissivity and high enthalpy for building energy saving

Summer heatwave events become more and more frequent, building cooling load continues to rise, and the traditional cooling method using air conditioning consumes a lot of energy. New technologies and materials with high efficiency, energy saving and low cost are urgently needed to solve the problem of high energy consumption in buildings. In this paper, by combining phase change storage technology with passive cooling technology of sky radiation, a new type of high-emission flexible composite phase change material (CPCM) was prepared using polypropylene hollow fiber (PP hollow fiber), Styrene-Ethylene-Butylene-Styrene (SEBS) and paraffin wax (PA). The prepared CPCM with excellent thermophysical properties, including a latent heat of 175.19 J/g, room temperature flexibility, the contact angle of the hydrophobic test of 129.15°, and the infrared emissivity of the atmospheric window of 0.942. The cooling experiment results show that the maximum temperature difference between CPCM and the environment is 2.6 °C lower than the ambient temperature. In addition, the simulation results show that the external surface temperature of the CPCM roof can be reduced by 23.15 K at the highest compared with a common roof, and the maximum energy saving can reach 13.24 W/m2. Compared with the high emissivity roof without CPCM, the external surface temperature is further reduced by 0.47K, the delay time is 50min, and the maximum energy saving can reach 0.76 W/m2. It's worth getting excited that CPCM can delay the opening time of air conditioning for 10 days. In addition, the application efficiency of cities in typical climate regions is simulated, and outstanding energy-saving efficiency is obtained, among which the maximum saving energy in Guangzhou is as high as 20.16 W/m2. The successful preparation of the novel CPCM material provides a new direction for the development of radiation-cooling technology.