Application Research of LED Lighting Fixtures in Highway Tunnels

Abstract: The construction scale of highway tunnels has been expanding in recent years. At the same time as the rapid development of tunnel construction, the high cost investment and high operating costs of highway tunnel lighting have restricted the development of highway tunnels. In order to meet the rapid development of the ever-expanding tunnel construction, the related content of tunnel lighting was studied to save operating costs. Combined with the example of a highway tunnel lighting, the advantages of LED lighting are studied, and the advantages of road tunneling are applied. The LED lighting and ordinary high-pressure sodium lamps are compared and analyzed, indicating that LED lighting is a very energy-saving green lighting. It provides a new way of thinking for solving tunnel lighting.

A road tunnel is an underground structure in a highway structure that is different from a bright road outside the cave. During the day, the vehicle enters the cave. Due to the sudden drop in brightness, the human visual reflection lags behind to form a “black hole effect”. It is difficult to distinguish the inside of the cave; when the vehicle exits the tunnel, a “white hole effect” is formed, which causes strong glare.

The nighttime situation is exactly the opposite of the daytime. This kind of difference in brightness between inside and outside the hole, when entering or exiting the tunnel, the human eye needs to adapt to the time, that is, the "adapted hysteresis phenomenon" occurs. In order to solve the visual adaptation process of the tunnel entrance brightness from light to dark or from dark to bright, the driver can clearly identify the target or object on the road surface, eliminate visual and psychological obstacles, and does not affect driving safety. The Design Code for Highway Tunnels (JTG D70-2004) stipulates that tunnels with a length > 100 m should be illuminated. Highway tunnel lighting is designed to create a good working visual environment within the cave, ensuring that vehicles traveling during the day and night approach safely approach and traverse the tunnel at design speed.

Light Emitting Diode (LED) is a green light source that attracts attention in the 21st century. It is an energy-saving and environment-friendly light source with low power consumption, long life, vibration resistance and no radiation. Since 1998, in the short span of several years, the world's semiconductor and lighting field has set off a "hot" of white LEDs, making white LED technology continue to innovate and rapidly develop, and the luminous intensity and stability of LEDs can be greatly improved.

1 LED working principle and advantages

1. 1 LED lamp works

LED Chinese translated as "light-emitting diode", is an electronic device that can convert electrical energy into light energy, with the characteristics of a diode. The basic structure is an electroluminescent semiconductor module packaged in an epoxy resin, which acts as a positive and negative electrode through pins and serves as a support. The core of the LED is a wafer consisting of a P-type semiconductor and an N-type semiconductor. There is a transition layer between the P-type semiconductor and the N-type semiconductor, called the PN junction. In some PN junctions of semiconductor materials, the injected minority carriers recombine with the majority carriers to release excess energy in the form of light, thereby directly converting electrical energy into light energy. Such a diode fabricated by the principle of injection electroluminescence is called a light-emitting diode, and is generally called an LED. When it is in the forward working state (ie, plus a forward voltage at both ends), the electrons begin to move and the holes (positively charged ions) combine to produce radiant light. The light source is generated within a millimeter of the interface of the PN junction. The wavelength of the illumination depends on the characteristics of the material and has different illumination colors. Red, yellow, green and blue LEDs are common. The brightness of the LED can be adjusted by the operating voltage (current). In the large operating current range, the brightness of the LED increases with increasing current. Currently, different LEDs can emit light from different wavelengths from infrared to blue, and LEDs that are coated with phosphors on blue LEDs to convert blue light into white light.

1. 2 Advantages of LED lamps

LED luminaires have no stroboscopic, no radiation, are typical green lighting, and are a new source of eye protection. Instead of tungsten, the LED is made of a special semiconductor PN material. Illuminated by electronic motion. There is no ultraviolet or infrared light in the spectrum, so there is no flash and radiation, which protects the eyes. Its main advantages are concentrated in the following points:

1) High luminous efficiency. LED lamps have low voltage, low current and high brightness. A 10 to 12 W LED source emits light equivalent to a 35 to 150 W incandescent lamp. The same lighting effect LED is 80% to 90% more energy efficient than conventional light sources, and is 4 to 8 times more than incandescent lamps.

2) The power consumption is extremely small. At the same brightness, the power consumption is only 1 / 8 to 1 /10 of ordinary incandescent lamps.

3) Long life. LED uses solid-state semiconductor chip to convert electrical energy into light energy, plus epoxy resin package, can withstand high-intensity mechanical shock, LED single-tube life is 100,000 h, light source life is over 20,000 h, and life is 12 h per day. More than a year.

4) Reliable and durable, easy to transport long distances. Since there are no wearing parts such as tungsten wire and glass case in the body, it is basically not affected by transportation, the normal scrap rate is small, and the maintenance cost is extremely low.

5) The start response is fast, there is no blackhead, and the trouble of replacing the lamp is eliminated. The LED starts to respond very quickly, so the current has little impact on it. The ordinary incandescent lamp or the energy-saving tube is affected by the starting current, and the lamp cap is easily blackened and needs to be replaced.

6) Since the LED tube is composed of more than ten or dozens, even if it is damaged, it will not have much influence on normal lighting. Unlike the high-pressure sodium lamp, the whole lamp is extinguished, so the reliability of the LED lamp is higher than that of the high-pressure sodium lamp. The reliability has increased many times.

7) No mercury is added to the light source, which is good for environmental protection.

A comparison of the performance of LED luminaires with conventional luminaires is shown in Table 1.

Table 1 Performance comparison between LED lamps and traditional lamps

2 LED lights for tunnel lighting advantages

The types of light sources used in traditional tunnel lighting mainly include metal halide lamps, high-pressure sodium lamps, incandescent lamps, and energy-saving lamps (compact fluorescent lamps). Among them, the high-pressure sodium lamp has the advantages of high luminous efficiency, energy saving, moderate color temperature, and is most widely used in tunnel lamps. However, the advantages of LED tunnel lights compared to high pressure sodium lamps are:

1) LED as a point source can largely solve the problem of secondary light extraction and optical loss that traditional spherical light source must solve by light emission.

2) The uniformity of the light-irradiated surface can be controlled. In theory, it can be completely uniform in the target area, which can also avoid the waste of light in the traditional light source "light under the light" phenomenon.

3) The color temperature is optional, which is an important way to improve efficiency and reduce cost in different occasions. As a kind of light-emitting device, LED can control the brightness by changing the current flowing through the current, and can also change and adjust the color through the configuration of different wavelength LEDs. This makes it easy to convert the lighting mode of the tunnel in different environments.

4) More energy efficient. At present, the luminous efficiency of white LEDs is about 80Lm /W, which can save 50% to 60% compared with traditional high-pressure sodium lamps. With the rapid improvement of LED efficiency, LED tunnel lamps have shown great potential in energy saving.

5) Low maintenance costs. Based on the current technical level and test results, the high-power LED light source can be used normally for 5 to 10 years without replacement, while the traditional high-pressure sodium lamp is replaced once every 2 years or so. The use of LED light source can greatly reduce maintenance costs.

6) Better color rendering. LEDs have a high color rendering index (typically 75 to 80), and the road looks brighter, feels more comfortable, and the driver feels safer. The high-pressure sodium lamp has a narrow spectrum and poor color rendering (color rendering index is generally 20 to 40), and it feels dim.

The 100 W LED lamp has a luminous flux of only about 6,250 Lm, which is still around 6 000 Lm when it reaches the road, and the average illumination of the road can reach 16 Lx (12 m high pole). The output luminous flux of the 200 W high-pressure sodium lamp is 16 000 Lm, but only 6 000 Lm is reached on the road surface, and the illumination of the road surface is about 30 to 40 Lx. Due to the difference in color rendering coefficient, the illumination correction factor of the LED is 2.35 times. The correction factor of the high pressure sodium lamp is 0.94 times. Therefore, after the correction of the 100 W LED, the illuminance of the ground is 37. 6 Lx, and the corrected illumination of the high-pressure sodium lamp is 28. 2 to 37. 6 Lx, which are equivalent. Therefore, a 100 W LED can replace a high-pressure sodium lamp of about 200 W. From the actual luminous effect, the LED lamp is much better than the high-pressure sodium lamp.

3 luminaire layout example

Ningqiang to Cheppanguan highway tunnel lighting design using the new LED tunnel special lighting to replace the original design of high-pressure sodium lamps, the total lighting power is 0.6 times the original design, saving 40%. The lighting layout is:

Basic section luminaire layout: 60 W LED tunnel-specific lamps with a spacing of 10.0 m (cement pavement), 110 W LED tunnel-specific lamps, spacing of 1. 0 m (asphalt road).

6米。 The introduction of the segment of the luminaire arrangement: using 140 W LED tunnel dedicated lamp to enhance the illumination, spacing 0. 6 m.

Transition section I luminaire arrangement: illuminate with a 140 W LED tunnel dedicated light with a spacing of 2.0 m.

Transition section II luminaire arrangement: illuminate with a 140 W LED tunnel-specific lamp with a spacing of 8. 0 m.

Exit section: Add 2 盏 140 W of LEDs and 4 盏 110 W of LED tunnel-specific lamps to enhance lighting (asphalt) for each basic lighting segment.

Each basic lighting section adds 2 盏 140 W of LED tunnel-specific lights to enhance illumination.

See Table 2 for comparison of investment and energy saving of high pressure sodium lamps and LED lamps.

Table 2 Comparison of lighting optimization costs

4 Conclusion

At present, the initial investment of LED tunnel-specific lamps is higher than that of high-pressure sodium lamps, but the power consumption and maintenance cost of LEDs are much lower than that of high-pressure sodium lamps, and with the industrialization of LED lamps, the production cost will be greatly reduced, so LED lamps The application of road tunnels will soon become popular, and with the continuous application of more LED lamps, it will produce considerable economic and social benefits.

According to the statistics of the “Statistical Bulletin on the Development of Highway Water Transportation Industry” published by China every year, the annual increase of highway tunnel construction in China from 2006 to 2006 is more than 20%. At the end of 2009, the number of national highway tunnels was 6,139, 394.200 million m, an increase of 713 and 756,600 m from the end of the previous year, including 190 special long tunnels, 821,100 m, and 905 long tunnels, 150.07. Million m. If you add other types of tunnels such as railway tunnels, subways, light rails and overpasses, if 50% of them are equipped with LED tunnel lighting, it will bring huge economic benefits.

Therefore, LED lamps, as the fourth generation of electric light source, are called “green lighting source”, which will replace traditional incandescent lamps, tungsten halogen lamps and fluorescent lamps and become the next generation of light sources in the 21st century, especially with green energy – solar energy. When combined with batteries, white LEDs will be an ideal environmentally friendly lighting.

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