Characterization and performance enhancement of radiative cooling on circular surfaces

The performance of radiative cooling depends on the view factor between the cooling surface and the sky. To maximize cooling power, horizontal radiative cooling surfaces are usually adopted. However, non-horizontal surfaces that have only partial access to the sky are ubiquitous in the world, for example, tilted roofs, walls, and pipes, which hinder the penetration of radiative cooling technology to a wider range of applications. In recent years, some radiative cooling structures using infrared reflectors have been investigated. Nevertheless, the absence of study on the radiative cooling power in relation to the parameters of reflectors causes difficulty in designing and optimizing infrared reflectors for non-horizontal surfaces. Herein, we built a comprehensive model to characterize the angular distribution of cooling power on a circular radiative cooling surface. The key factors that affect the cooling power, e.g., reflectors’ geometry and spectral characteristics, are investigated. The model is then validated by experimental data. Furthermore, we proposed a method to design and optimize the dimensions and positions of the cooling surface and reflector. Results show that compared to the baseline condition without infrared reflectors, the total radiative cooling power of the circular surface has increased by 68.3% and 112.5% for flat reflectors and parabolic reflectors, respectively.