Optimization of photoluminescent materials for lighting energy saving in the built environment

In the last decades, fossil fuels have become the primary resource for electricity generation, contributing to the aggravation of problems like global warming and ozone depletion. For this reason, innovative solutions are being continuously developed in order to improve energy efficiency in the construction sector. Beyond heating and cooling, urban lighting plays a significant role on the final energy consumption of a city, including both indoors and outdoors. In this work, photoluminescent materials are investigated as possible light sources to be implemented in urban lighting systems, focusing on the free-cost and renewable luminous gain they provide after being exposed to a proper radiation. In particular, commercially available photoluminescent powders are evaluated by means of spectroradiometric techniques and using a specifically designed experimental setup. Measurements are repeated for different intensities and wavebands of irradiation to identify the most promising "pigment-lamp" combination in terms of (i) luminous intensity and (ii) photoluminescence duration. Results show that the shorter the distance between the emission spectra of the exciting source and the photoluminescent powder, the better the performance of the latter. Therefore, the choice of both afterglow and exciting source cannot be independent from the final system's application and the required end-use lighting level.