Optical-thermal modeling and geographic analysis of dusty radiative cooling surfaces

Radiative cooling for energy conservation and harvesting has gained considerable attention worldwide in recent years. The optical and thermal characteristics of radiative cooling surface at outdoors is susceptible to dust soiling. Currently, limited research has been devoted to this problem. This work presents a model utilizing the beam envelope method and effective medium theory to investigate the optical characteristics of radiative cooling surfaces impacted by dust soiling. Subsequently, an optical-thermal coupling model is developed to investigate the spectral emissivity, average absorption/emission rates, and net heat gain of radiative cooling surfaces affected by dust soiling. The effect of dust soiling on the absorption of solar radiation is evident, with a substantial effect observed, but its impact on emissivity in the atmospheric window bands is comparatively minor. Meanwhile, it could be noticed that the mechanisms by which various material parameters of dust layers impact optical characteristics are different. In addition, the integration of the optical-thermal coupling model with EnergyPlus meteorological data and MERRA-2 facilitates an exploration of the geographical distribution of radiative cooling power variations induced by dust soiling across different regions in China. It is concluded that regions in China with a higher potential for radiative cooling often characterized by elevated dust deposition rates and low precipitation, rendering them more susceptible to the adverse effects of dust soiling. Effective cleaning significantly enhances both the optical and thermal characteristics of radiative cooling surfaces. The findings of this study offer a theoretical foundation for the enduring application of radiative cooling technology.