Harvesting daylight with LED or T5 fluorescent lamps? The role of dimming

While the efficiency of the Lighting Emitting Diodes (LED) is increasing and new installations are being implemented, their control due to the adoption of daylight harvesting systems, hasn't been sufficiently examined yet, although this can reduce further energy consumption. A crucial parameter for achieving improved performance is the proper matching of a dimming system with the luminaires used, since this can significantly affect energy savings not only among various luminaires with T5 tubular fluorescent lamps but also among various LED luminaires. Furthermore, dimming can affect the power quality of the lighting installation depending on the technology used, making it an important factor during the selection phase. The aim of the present paper is to quantify energy savings among different LED and T5 fluorescent luminaires that are commonly used with daylight harvesting systems in offices and investigate their impact on power quality. Measurements using four commercial LED and four T5 luminaires were performed estimating the mathematical function which correlates their light output with their associate power consumption. Using the measured data, a set of hourly annual simulations were performed for a photosensor installed in a typical office room, quantifying the relative differences in energy savings among various cases examined together with the power factor values. (C) 2017 Elsevier B.V. All rights reserved.