A study on the thermo-optical behaviour of phosphorescent coatings for passive cooling applications

Abstract

Climate change intensifies the Urban Heat Islands (UHI) in hundreds of cities around the globe. Even though tests on traditional cool materials have shown promising results in terms of UHI mitigation, novel advanced solutions are deemed necessary for strategically counteracting UHI. Unlike traditional materials, phosphorescent materials can not only reflect incident shortwave radiation but also reemit it back, i.e. the phenomenon of phosphorescence. Even though this unique reflection-reemission mechanism known as effective solar reflectance (ESR), has been widely tested for sustainable lightning applications, its cooling potential has been surprisingly overlooked. Here, we examine, in-lab, and numerically, the thermo-optical properties of several phosphorescent coatings of different colours and we evaluate their effective cooling potential. Results reveal that the phosphorescence mechanism could be effectively optimized for obtaining phosphorescent-based coatings with an improved optical performance and hence substantially mitigate surface overheating in the built environment.