Energy efficiency in outdoor lighting applications: potentials of photoluminescent light spots

In recent decades, several passive solutions have been developed with the aim of reducing the ever increasing energy consumption and greenhouse gas emissions related to the built environment. Photoluminescent materials among others are an avant-garde solution for passive cooling applications, yet, their light emission capability upon exposure to the proper light source, also provides room for possible integration in lighting systems for energy saving purposes. In this context, the present work aims at producing and experimentally investigating the long-term light emission of zero-energy photoluminescent glass grits-based elements, when integrated in outdoor lighting systems. Commercially available strontium aluminate-based photoluminescent glass grits with dysprosium and europium dopants, were used to produce 4 types of zero-energy consumption light spots, emitting in the yellow or blue region of the visible spectrum, according to their chemical composition. The developed experimental campaign aimed at evaluating the best performing sample and, subsequently, at investigating the effect of realistic boundary conditions on its luminescent behaviour. The different samples were exposed to direct sunlight and to the radiative flux from a solar simulator, and their irradiance profile was monitored during the decay time. The obtained values demonstrate how the mix between yellow and blue fine glass grits results in the best performing spot.