Investigation of photothermal regulation strategies of a phase change material blind in a ventilated double skin façade system

Double skin facades (DSFs) are widely used in modern buildings due to their aesthetic appeal, good lighting, and thermal buffering properties. However, its overheating problem in summer and heat loss in winter often leads to high energy consumption, room temperature fluctuation and poor thermal environment. Previous studies have attempted to improve the thermal performance of the system by integrating phase change materials (PCMs) into the shading devices. However, most of them adopted opaque metal shell blinds, which adversely affect the light transmittance of the DSFs and indoor light environment. In this paper, a novel PCM blind with a transparent shell was proposed for integration into the DSF system. An experimental study on the proposed system was carried out during both heating and cooling seasons. Various ventilation modes and blind control strategies were proposed for different working conditions during heating and cooling seasons. Then, a coupled coordination model was developed for evaluating the performance of PCM-DSF system in achieving proper indoor light and heat environment. The results show that in the heating season, it is recommended to set the PCM-DSF system with external circulation ventilation mode, with tilt angle between the range of 40~65°. In the cooling season, the PCM-DSF system in the internal circulation ventilation mode showed better solar thermal performance. On sunny days, 0~25° was the effective regulation range of blade tilt angle, and the blind tilt angle of 0° was recommended since the system has the best comprehensive photothermal performance. Under cloudy conditions, 0~35° was the effective control range of blade tilt angle. When the blind tilt angle was set to 10°, the system performance reached the optimum, and the system can achieve balance between natural daylighting and indoor thermal comfort.