Abstract: To minimize the energy consumption in tunnel entrance lighting, a novel efficient solar direct lighting system is proposed. The system integrates lighting system, transmission system, and exit system, with a light utilization rate reaching over 60%. The lighting system uses a novel self-developed free-form surface lens, and employs the four-quadrant photoelectric detection method as the light tracking algorithm. The transmission fiber of the transmission system adopts the quartz fiber with large optical capacity, low transmission loss, and strong bending resistance. Based on theoretical deduction and field test, the coupling head height of the fiber is obtained when the system light utilization rate reaches the maximum. The exit taillights can secondarily distribute the transmitted light, and the distribution of light intensity after distribution is close to that of the commonly used LED lights in tunnels. Based on the test results of this system, the following conclusions are obtained: (1) The brightness of the road surface in different seasons and times is greater than the brightness specified in the standards, meeting the requirements of driving safety. (2) An energy conservation of more than 65% is achieved compared to traditional electro-optical lighting scheme, and a 24.4% cost within 10 years of service life can be saved, showing energy and economic benefits.

Key words: highway tunnel, direct sunlight illumination, tunnel lighting, energy conservation, traffic safety