Numerical techniques for electromagnetic simulation of daytime radiative cooling: A review

Abstract

Radiative cooling is a well-researched cooling technique based on the ability of terrestrial surfaces to dissipate heat to the cold space. Past research on radiative cooling failed to present sub-ambient temperatures under direct sunlight due to the limited solar reflectance and emissivity in the atmospheric window. Nanostructures developed in recent years have successfully achieved sub-ambient feature during the daytime. The use of electromagnetic simulation in the design of such structures is essential to understand their optical properties and thus optimize the structures and materials selected before manufacture. In this paper, the commonly used software to solve Maxwell's equations is first reported. Then the numerical techniques are reviewed and their advantages, limitations, and popularity in academic research are compared and analyzed. After that, the application of these numerical techniques in daytime radiative cooling and the extent of the agreement between their results and those of a reference are discussed. The accuracy analysis of these numerical techniques-including the source of errors in the original calculation, how accuracy of the result is evaluated, and explanations for the discrepancies in results between original and reference computations-are discussed in the final part, as well as the characteristics of numerical technique preferred in radiative cooling. The purpose of this paper is to provide strategies for selecting appropriate numerical techniques according to specific needs, evaluating, and analyzing the accuracy of the calculations, and explaining the cause of discrepancies between original and reference computations.