Lighting systems energy efficiency based on different human visual conditions

This paper presents a lighting design analysis in scotopic and photopic conditions of different lamps types. The efficient lighting system concept is usually associated with high performance electronic circuits. However, researches related to the human eye physiology indicate that this efficiency gain can be achieved only by changing the lamp type to be used in each visual condition. Analysis suggests that changing the light spectrum incident on the eye, so that it excites most effectively the photoreceptor cells, light levels can be reduced without compromising the visual performance. On this basis, this paper presents a study comparing the power required, the lighting system investment cost, and the energy consumed cost over 10 years. Therefore, lighting systems based on high pressure sodium lamps, fluorescent lamps, metal halide lamp, and lighting emitting diodes are compared. The final results show that the most efficient lighting system for photopic conditions is based on high pressure sodium lamps. However, under scotopic conditions the best efficiency is obtained with the use of metal halide lamps.