Photo-thermal coupling effect and energy performance of phase change material integrated double skin façade system

Double skin façade (DSF) systems have the potential to improve both thermal performance and daylight utilization; however, pronounced seasonal variations in solar radiation and thermal demand make conventional operating strategies based on fixed blind angles or single ventilation modes insufficient to balance shading, daylighting, and energy use. Existing studies have primarily focused on thermal or geometric optimization, while the photothermal coordination of shading devices and seasonally adaptive operation remains insufficiently explored. In this study, a DSF system integrated with phase change material (PCM) blinds (PCM-DSF) is proposed, and its photothermal behavior and energy performance under different operating conditions are evaluated using a combined experimental and annual EnergyPlus simulation approach. Results indicate that under high solar radiation conditions (outdoor temperatures above 30°C), an external ventilation mode combined with a larger blind tilt angle (60°) effectively reduces solar heat gains while maintaining acceptable daylight levels. Under low ambient temperature conditions, an internal ventilation mode with a smaller tilt angle (10°) enhances PCM heat storage and release, increasing heat storage efficiency by approximately 27%. In addition, PCM blinds reduce heating, ventilation and air-conditioning (HVAC) and lighting energy consumption by up to 6.8% and 17.1%, respectively, compared with conventional aluminum blinds. These results demonstrate that coordinated regulation of blind tilt angle, ventilation mode, and phase change temperature enables effective photothermal optimization of DSF systems, offering practical guidance for energy-efficient and climate-responsive building operation.