Comparative Study of Energy Savings for Various Control Strategies in the Tunnel Lighting System

Tunnel lighting is the most significant component in total energy consumption in the whole infrastructure. Hence, various lighting control strategies based on light-emitting diode (LED) technology have been investigated to conserve energy by decreasing luminaires' operating time. In this study, four kinds of tunnel lighting control strategies and the development of their associated technologies are evaluated: no-control low-consumption lamps (LCL), time-scheduling control strategy (TSCS), daylight adaptation control strategy (DACS), and intelligent control strategy (ICS). This work investigates the relationship between initial investment and electrical costs as a function of tunnel length (L) and daily traffic volume (N) for the four control strategies. The analysis was performed using 100-day data collected in eleven Chinese tunnels. The tunnel length (L) ranged from 600 m to 3300 m and the daily traffic volume (N) ranged from 700 to 2500. The results showed that initial investment costs increase with L for all control strategies. Also, the electricity costs for the LCL, TSCS, and DACS strategies increased linearly with L, whereas the electricity cost for the ICS strategy has an exponential growth with L and N. The results showed that for a lifetime equal to or shorter than 218 days, the LCL strategy offered the best economical solution; whereas for a lifetime longer than 955 days, the ICS strategy offered the best economical solution. For a lifetime between 218 and 955 days, the most suitable strategy varies with tunnel length and traffic volume. This study's results can guide the decision-making process during the tunnel lighting system's design stage.