Assessing energy saving potential of wavelength-dependent passive daytime radiative cooler implemented with EnergyPlus by a roof model

Abstract

The Passive Daytime Radiative Cooler (PDRC) exhibits potential in enhancing building energy conservation due to its high emissivity in wavelength between 8 μm and 13 μm. However, current building energy simulation programs, e.g., EnergyPlus, generally adopt a constant emissivity. To implement the wavelength-dependent PDRC model into EnergyPlus, a roof model was introduced to couple it with EnergyPlus to assess the energy saving potential of PDRC more reasonably. To assess the PDRC roofs, the impact of buildings constructed in different eras, building heights, and climatic conditions in China on building energy saving was investigated. The results showed that more energy was saved in regions with high cooling demands e.g., Shanghai and Guangzhou. Applying PDRC on roofs of buildings constructed pre 2001 in severe cold regions increased building energy consumptions. Furthermore, buildings with well insulated roofs coated by PDRC were not equally beneficial for reducing cooling demands in summer compared to buildings with non-insulated roofs, but heating demands in winter could be reduced. With an increase in building height, the energy saving potential of PDRC roofs was reduced. Therefore, a comprehensive analysis was imperative considering the local climates as well as the building itself when PDRC is to be applied.