A novel radiative cooling system with a dissimilar material-based compound parabolic concentrator for mitigating daytime solar radiation impact

Radiative sky cooling (RC) is a promising passive heat dissipation technology for building energy conservation but suffers from sensitivity to daytime solar radiation and an inherently low cooling power density. To address these challenges, a novel dissimilar material-based compound parabolic concentrator (DCPC) is first proposed and integrated into an RC system. The asymmetric DCPC features a dissimilar material design: a transparent wing framework covered with a transparent infrared-reflective film (TIRF) on one side and a high-reflectivity mirror wing on the other, aiming to enhance solar shielding while maximizing thermal emission for RC panels. In this work, a mathematical model, validated through experiments conducted in Nottingham, UK, is developed to explore the effects of TIRF's optical properties and the module's tilt angle on cooling performance. Effects of diverse tilt angles for the DCPC-RC module are also analysed based on annual solar profile angles. The experiment results demonstrate that the DCPC-RC module's emitter can achieve sub-ambient temperature during the daytime. When located in Rome and tilted at 30° toward the anti-sunward side, it achieves an average cooling power density of 135.24 W/m2 within the solar profile angles of 40–50°, a 22.7 % increase over the horizontal module. This work establishes the DCPC-RC system as an efficient and scalable solution for enhancing passive cooling performance in energy-efficient buildings across diverse climatic conditions.