Enhancing radiative sky cooling performance by employing crossed compound parabolic concentrating configurations

Achieving superior radiative sky cooling (RC) performance in practical applications is challenging due to its cooling power is easily compromised by unwanted thermal energy influxes, including solar heat gain and thermal radiation from nearby warm objects. To address this issue, the present work introduces the integration of affiliated crossed compound parabolic concentrators (CPC) as a means to effectively mitigate this thermal burden. Through the development of a comprehensive mathematical framework that characterizes the heat exchange between the RC emitter and different environmental heat sources, the cooling performance of the novel crossed CPC-RC module is evaluated and compared with other RC configurations. The results show that due to its excellent capability to shield unfavourable heat inflows from large zenith angles, the crossed CPC-RC module shows the potential to reach a cooling power density of 99.50 W/m2 at noon, outperforming the flat-RC and 2D CPC-RC modules by 5.1% and 41.7%, respectively. Furthermore, key parameters optimization and the cooling performance assessment throughout a typical summer day is carried out to demonstrate the superiority of the crossed CPC structure in boosting cooling capacity, particularly the cooling benefits throughout the day, thereby offering a promising solution to better align with the cooling demands of buildings.