Computational optimization of unglazed double skin transpired solar collectors on building facades

Efficient thermal energy collector systems are vital to minimize heating demands and promote sustainable energy systems. One such system that utilizes solar energy and converts it into useful heat is transpired solar collectors (TSCs). These systems are typically integrated into building facades to pre-heat ventilation systems, thereby reducing reliance on fossil fuels. However, the conventional TSC designs have generally lower thermal efficiency due to non-uniform airflow distribution and localized overheating within the plenum. In this study, a numerical investigation is conducted to optimize the design of an Unglazed Double Skin Transpired Solar Collector (UDS-TSC) using validated CFD simulations. The simulations investigate the effect of three critical performance parameters: (1) separation plate placement, (2) shape of separation plate, and (3) and duct configuration. The results show that placing the separation plate at the mid-location between the absorber plate and the building wall maximizes the heat exchange effectiveness, yielding a peak value of ε HX = 0.505. Among the geometric configurations investigated, the flat separation plate outperforms corrugated designs, producing a higher outlet air temperature (41.1 °C) and improved heat exchange effectiveness due to reduced flow resistance and air stagnation. Furthermore, a novel top-ducted configuration is proposed in this study to reduce localized overheating in the upper plenum region. This configuration increases the heat exchange effectiveness to 0.661, corresponding to a 15.6% improvement over the baseline UDS-TSC, while simultaneously eliminating stagnant high-temperature zones. The findings of the present study clearly demonstrate that the geometric and the ducting configuration optimization can significantly enhance the thermal performance and operational reliability of facade-integrated UDS-TSC systems for building ventilation and air-heating applications.