Management optimization of the luminous flux regulation of a lighting system in road tunnels

Lighting very long road tunnels implies a high consumption of electrical energy since it requires a proper illumination during the whole day. In particular, in the daytime the illuminance levels right at the entrance and exit zones must be higher than those characterizing the inside of the tunnel, in this way the eye of the driver is able to adapt and be safe while passing from a high natural illumination of the outside to the lighting conditions characterizing the inside of the tunnel; consequently this causes a high energy demand. Therefore this case study investigates whether it is possible to minimize the energy demand through the exertion of an automatic new control system regulating the luminous fluxes of artificial sources (guaranteeing the parameters set by the regulation) with respect to the variation of the natural light characterizing the outside. The innovative control systems must be characterized by high reliability levels in order to guarantee conditions which are not dangerous to the driver if an outage occurs and minimize their maintenance costs. To carry out this type of study the software DIALux was used to simulate a tunnel with a dimming system (with lamps characterized by a high luminous efficiency) regulated by a pre-programmed logic control system (with high MTBF values). The savings obtained enabled the amortization of the solution here suggested in a time interval which makes it an advantageous choice economically speaking.