ABSTRACT
ABSTRACT: Photonic crystal approach is a newly developed energy-free radiative cooling method for buildings with distinguished advantages in terms of both reflecting sunlight efficiently and emitting indoor thermal radiation selectively. However, the application on windows requires remarkable visible light transparency and complicated photonic band gap arrangement, which leads to immense difficulties in quantifying the optimal number and individual thickness of film layers. This paper presents the design progress of photonic cooling film under approximate direct sunlight (0-20° incidence) by genetic algorithm, which is modified during the process of selection, crossing, and mutation. After validation by sensitivity analysis, the computational results indicate an average transmittance of 54% for visible light and 86% for indoor thermal radiation, while showing an average reflectivity of 73% for ultraviolet radiation and 80% for near-infrared radiation. Moreover, the net cooling power of the optimal design was as high as 108.7 W · m−2.
