Performance evaluation of a novel rotatable dynamic window integrated with a phase change material and a vacuum layer

Abstract

A glass window filled with a phase change material (PCM) can effectively increase the thermal inertia of a building envelope and achieve peak load transfer. However, conventional PCM windows have low energy efficiency, and the PCM layer has a risk of overheating. To improve the building energy efficiency and avoid the overheating of PCM windows, a new type of rotating dynamic PCM window (DPCMW) was designed in this study. The window comprised a PCM layer and a vacuum glass layer. The DPCMW could adjust the relative position of PCM and vacuum glass layers according to the time; thus, the heat flux direction could be changed to reduce the building load. A theoretical model of the DPCMW was established and verified. The performance of the DPCMW was investigated under the Cfa climate, and the effects of the phase transition temperature, PCM layer thickness, and PCM phase transition temperature range on the performance was discussed. The results indicate that the performance of the DPCMW exceeds that of a static PCM window (SPCMW) in both winter and summer. The DPCMW reduces the heating load relative to the SPCMW by 12.40% in winter and reduces the cooling load relative to the SPCMW by 93.79% in summer. The DPCMW reduces the annual building load by 28.70% relative to the SPCMW. Additionally, the optimal phase transition temperature is 23–25 °C. The thicker the PCM layer, the better the energy-saving effect, and the optimal phase transition temperature range is 19–25 °C. This study provides a theoretical basis for the application of the DPCMW.