Can solar LED lighting in highway tunnels replace existing conventional lighting systems?

1 Introduction

With the rapid economic development, my country's electricity demand has been growing at a rate of more than 20% per year. According to the current economic development trend and China's resource situation, the electricity supply in 2010 and 2020 will not be enough to rely solely on traditional coal, water and nuclear power. There is still a certain gap that needs to be filled by renewable energy generation. The conventional lighting system currently used consumes a lot of electricity, is expensive and has safety hazards. Therefore, driven by the "Highway Tunnel Solar Lighting System Research" project proposed by the Western Transportation Construction Science and Technology Project Management Center of the Ministry of Communications in 2004, relevant research has been carried out in China.

2 Analysis of domestic research status

The development of highway tunnel lighting fixtures in my country started late and has a poor foundation, especially in-depth research on tunnel lighting fixtures and characteristics is lacking, and there is a big gap between the designed and manufactured fixtures and those abroad. In recent years, except for Fudan University, Shanghai Lighting Research Institute, Chongqing Transportation Research and Design Institute, Zhejiang Transportation Planning and Design Institute, etc., which have research conditions and certain test equipment and have gradually begun to pay attention to tunnel lighting research, most lighting manufacturers do not have research conditions and test equipment for highway tunnel lighting, and their ability to independently develop tunnel lighting is poor. Most domestic tunnel lighting factories are small factories or mainly engaged in the production of lighting equipment in other fields, with backward technology, processes and equipment, scattered production, low level of specialization, and low efficiency.

In the development of highway tunnel lighting fixtures in my country, there is a lack of sufficient understanding and necessary investment. Compared with the concentration of foreign lighting electrical industry production, it is far from the expected economic scale. Once a highway tunnel is put into use, the lighting system is almost always lit under normal conditions. Therefore, the tunnel lighting effect must be achieved with a reliable light source, and choosing a suitable light source is an important part of long-term tunnel lighting. However, most of the tunnel lamps used in China have problems such as narrow light band, insufficient light distribution quality, high energy consumption, poor quality stability, short life, and low grade, which directly lead to poor highway tunnel lighting effects and cannot meet the requirements of highway tunnel lighting, seriously affecting driving safety. Therefore, the light source of tunnel lighting should meet the requirements of light efficiency, luminous flux, life, light color and color rendering in the specific environment of the tunnel, and at the same time ensure good visibility in the smoke formed by automobile emissions.

Therefore, in order to reduce the total power consumption of short and medium tunnel lighting systems, reduce the cost of solar power supply systems, and meet the lighting requirements far away from power supply sites, domestic and foreign countries, under the tremendous pressure of energy conservation and environmental protection, have adopted relevant policies to encourage and promote LED lighting products to reduce system power consumption.

In recent years, with the continuous improvement of the research level of LED technology, the research on the use of LED lighting has gradually deepened. In terms of LED technology research, the Light Research Center in Boston, USA, has developed a semiconductor light source with blue and yellow wavelengths, which emits light that people feel as white light. The luminous efficiency of this LED is 10 times or even higher than that of the LED on the current market, but it has not yet been commercialized. Another company, OSRAM OS, has developed a thin MD that is only 6mm high and is edge-mounted. It injects light into a light-guide material, and the light is evenly distributed on the surface. This module can be used by lighting manufacturers and built into products for directional lighting of channels, corridors, theaters or cinema seats. The module energy consumption ranges from one watt to several watts.

As for LED-related products, Austrian lighting design company uses 14,000 white and colored LEDs to illuminate the entire room, with a light level of 600-700 Lux, which is enough for an ordinary office. The computer calculates the mixing effect of white, blue, blue/green, amber and red diodes to obtain a warm color temperature of 2500-3000K, and its color rendering index is very close to the best fluorescent lamps.

In Sweden, the Swedish National Road Administration uses LEDs for traffic lights to reduce the need for traditional traffic lights that generate a lot of heat.

In 2005, ASSIST, a solid-state lighting system and technology alliance formed by eight major corporate groups in the United States, Japan and Europe, formulated the "LED lifespan for general lighting" technical standard, which stipulates the definition, device and system measurement methods of general LED lifespan.

In the same year, Japan introduced a tax law to promote the improvement and increase of energy use, which clearly stipulates that enterprises or institutions that use LED lighting to replace incandescent lighting can obtain 130% excess depreciation of the investment amount, or a tax reduction of 7% of the investment amount. In July 2006, the European Union began to implement the "Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment", restricting the use of mercury-containing fluorescent tubes; California legislators proposed to implement a ban on incandescent lamps by 2012; in February 2007, the Australian government announced that it would gradually phase out incandescent lamps.

Domestic LED is only in the initial stage of lighting application. In order to make LED really enter the lighting field, the national "863" plan provides funding for the new materials field, which has made significant progress in related industries. Some scientific research institutes, such as the Institute of Physics of the Chinese Academy of Sciences and the Changchun Institute of Optics, Fine Mechanics and Physics, Peking University, Beijing Institute of Nonferrous Metals, Shijiazhuang Thirteenth Institute and other units have also carried out research work in this area. At present, gratifying progress has been made, and the gap with the international advanced level is being narrowed. Most of the white light LEDs on the market are self-packaged by domestic LED manufacturers using imported chips and phosphors. Due to weak technical strength and independent development capabilities, the selection of blue light chips and the performance of white light LEDs are subject to certain restrictions and influences.

As a result, semiconductor lighting has gradually entered the field of highway tunnel lighting, challenging traditional lighting fixtures. Several well-known companies have launched samples of this type of light source. It can be seen that with the rapid development of LEDs at home and abroad, there are price barriers on the road to popularization of corresponding product development, but its high cost performance has greatly made up for this shortcoming. Especially in the fields of transportation, as the industry continues to develop, LEDs have received more widespread attention, such as road signal lights, strobe warning lights, variable information boards, etc. In particular, in 2004, the Western Construction Management Center of the Ministry of Transportation proposed the "Highway Tunnel Solar Lighting System Research" project based on solving the problem of highway tunnel lighting with no power supply conditions or poor power supply conditions. While the first solar LED lighting system tunnel in the country was built in Jilin Province, many LED lighting system tunnels with conventional power supply have been completed in China.

At present, the LED lighting systems for highway tunnels that have been built are divided into two categories. One is the different lamps such as 50W, 80W, 120W, and 210W developed for expressways, which use relatively high-power lamps and are arranged continuously without light spots or small light shift effects, such as the Xiaopanling Tunnel in Jilin Province, the Longtoushan Tunnel in Guangdong Province, the Huangzhushan Tunnel in Jiangxi Province, the Duchuankou Tunnel of the Zaoxiao Expressway in Shaanxi Province, and the Caoyuan Tunnel of the Quansan Expressway in Fujian Province; the other is for ordinary roads and tunnels with poor power supply conditions, which use low-power lamps and are arranged at intervals to reduce power consumption, reduce power supply costs, and achieve solar power supply as the purpose of the setting method, such as the Garden Tunnel of Chaochang Highway in Jilin Province.

3 Conclusion

At present, in the research and application development of highway tunnel solar LED lighting systems in China, the following problems need to be further solved:

(1) The brightness of LED lighting decays quickly, and its service life needs to be further extended.

(2) Application standards of new lighting fixtures in highway tunnels.

(3) Reasonable configuration of solar power supply system in winter and rainy weather.

In summary, there is still a long way to go before the solar LED lighting system in highway tunnels replaces high-pressure sodium lamps and conventional power supply systems, especially the LED attenuation problem, which directly affects the service life of lamps. In other words, whether from the perspective of improving LED lighting technology or improving the level of solar energy application, promoting the application of solar LED lighting in highway tunnels has positive significance.