Laboratorial investigation on optical and thermal properties of cool pavement nano-coatings for urban heat island mitigation

Abstract

Urban Heat Island (UHI) effect causes the increasing energy consumption for building and environment cooling. Reflective coating is an effective cool pavement technology to counterbalance UHI. However, the investigation of the optical properties and their relation of colored reflective pavement coatings at full solar spectrum are still in its infancy. This paper prepared ten non-white coating samples to evaluate the optical properties and thermal performance of pigments and coatings. It was founded that color lightness is a dominant factor of visible reflectance however it does not affect the near-infrared reflectance. The coatings doped in chrome achieved reflectance around 60% and the near-infrared reflectance was as high as the white coating around 95%. The relation between lightness and visible reflectance was linear for coatings in dark and medium color while the exponential growth was shown for the coatings in light color. Based on the statistical analysis, the visible and short wave near-infrared reflectance (400 nm–1100 nm) were the dominant factors to influence thermal performance of coatings. The investigated results could provide insights and references for optimizing the design of reflective cool pavement coating and developing the metameric matching colored coatings without glare and aesthetic problems to mitigate the urban heat island effect.