LED Flood Lights
The advantages and installation matters of LED Tunnel Light
  • November 30,2018.
LED tunnel lights are used in tunnels, workshops, large warehouses, venues, metallurgy and various types of factories, construction and other places for large-area floodlighting, which are most suitable for urban landscapes, billboards, building facades for landscaping lighting.

Advantages of LED Tunnel Lights:

LED VS. Traditional source: LED is a solid-state semiconductor device that converts electricity directly into light.

Compared to traditional tunnel light sources (sodium lamps, metal halide lamps, etc.), LED sources have the following advantages:

(1) Low light decay. If the heat dissipation condition is good, the light decay in first 10000H of LED is positive light decay, which is 3%~10%, and the light decay in first 50000H is basically 30%, which is far lower than the ordinary road lighting source, and the luminescence is more stable.

(2) High color rendering. The color rendering of general LED light is about 70 to 80, which is higher if using three-color phosphors. The color rendering of general high pressure sodium lamps is 20 to 35, while the color rendering of low pressure sodium lamps is lower, so even the brightness of traditional light sources is higher than LED, but the visual effect is worse than LED. ‘Not the brightest, but the most clear’ should be a direction of LED light source application development.

(3) Lifespan. The lifespan of LED is higher than that of general road tunnel light sources, which is now generally higher than 50000H.

(4) Price. Although the current price of LED light is higher than that of traditional lighting, with the maturity of manufacturing technology, its price is falling sharply.

In addition, LED also has the advantages of high maintenance factor, good safety performance, no stroboscopic and energy saving and environmental protection.

Foreground challenge

At present, among the light sources used in tunnel lighting applications, high-pressure sodium lamps have been used for large-scale applications because of their high visual light efficiency (up to 120 lm/w), but high-pressure sodium lamps in the funnel lighting, there are still some difficult to overcome problems in poor color rendering and limited choice of light source power (usually only 250W and 400W), especially in the internal segment lighting. The high-pressure sodium lamp has no lower power on the one hand, on the other hand, the glare and stroboscopic light caused by the light source are more serious. In some long tunnels, straight tube fluorescent lamps have also been used for their high color rendering and good visual inductivity.

However, due to the short lifespan of fluorescent lamps, which is usually only about 8,000 hours, so they often need to be replaced, greatly increasing the maintenance cost. In addition, the power of the fluorescent lamp is low, so it is impossible to meet the requirements in areas such as the inlet section, the transition section, and the exit section where higher illumination is required. In recent years, with the maturity of the technology of induction lamp, the influence of the electrode factor is eliminated, so the induction lamp has a longer lifespan than the conventional fluorescent lamp, and can also achieve greater power, which makes the induction lamp show its advantage in the tunnel lighting situation. However, the luminous surface of the induction lamp is larger, and the optical efficiency of the entire lamp is lower during the optical design.

Although there are still many difficulties and challenges in the large-scale application of LED tunnel lights, such as the imperfect standard of LED lighting products, the negative impact of some inferior products on market promotion, and the high purchase cost of LED tunnel lights. These all put pressure on the large-scale market application of LED tunnel lights, but these pressures are inevitably encountered in the initial stage of any new technology and new products. However, with the further development of high-power white LED technology, LED tunnel lighting thermoelectric system technology continues to mature, people's energy conservation and environmental awareness are further enhanced, LED technology will certainly create a new future in the semiconductor lighting industry in tunnel lighting applications.

Installation method

LED tunnel lights have various installation methods, such as ceiling type, suspenders type, seat type, wall hanging type, etc., which are easy to operate and meet the needs of different work site lighting. The integrated design of the lamp and the electrical box has strong overall reliability, low failure rate, and safer and more convenient use and maintenance. The LED tunnel light can adopt intelligent control technology to realize its own dimming control and save energy. The long tunnel is provided with LED tunnel lights according to the double-hole one-way driving mode. The tunnel lighting is divided into entrance section, transition section 1, 2, 3, basic section and exit section. The lighting function is divided into enhanced light, full day light and emergency light three kinds. Double side lighting, the installation height of the lamp is 5.5 meters.

Road tunnel lighting has its own characteristics, it is different from common road lighting. The following points should be considered in design,

1, The road surface should have a certain brightness level
2, The tunnel wall should have a certain brightness level
3, The design needs to take into account many influencing factors, such as speed, traffic volume, route alignment, etc.
4, Comprehensively determine the level of lighting from aspects such as driving safety and comfort
5, Human visual adaptability, especially at the entrance and exit sections of the tunnel

6, Tunnels also require lighting during the day, and daytime lighting problems are more complicated than at night.

In order to save energy, improve lighting effect and ensure the safety and comfort of driving in tunnel lighting, it can usually be considered from the following aspects,
1, brightness
Due to the brightness outside the tunnel during the day is much higher than that in the tunnel, when the driver drives into the tunnel, the vision needs to have a certain adaptation time, and then the inside of the tunnel can be seen. This phenomenon is called ‘adapted hysteresis phenomenon’. If there is no proper transition, will produce a ‘black hole phenomenon’, make the driver temporarily lose normal visual function, which will bring security risks. ‘The black hole phenomenon’ is a visual problem that occurs before entering the tunnel and is also the most important problem in tunnel lighting. Tunnel lighting is usually divided into entrance lighting, interior lighting and exit lighting. The brightness of the daytime tunnel entrance lighting is determined by the brightness outside the tunnel, the speed of the vehicle, the field of view at the entrance, and the length of the tunnel. The threshold segment is to eliminate the ‘black hole phenomenon’, and the illumination level of the transition segment is further gradually decreased, thereby providing the driver with time for visual dark adaptation.

2, brightness uniformity
Good visual function not only requires a better average brightness, but also requires that the average brightness on the road surface should not be too different from the minimum brightness. If the difference in brightness in the field of view is too large, the bright part will form a glare source, and the change of light and dark will bring about a certain stroboscopic effect, which will affect the vision, and the visual effect of the human eye will be significantly worse, and the vision Fatigue will also increase.

The overall brightness uniformity U0 refers to the ratio of the minimum brightness to the average brightness on the road surface inside the tunnel. The longitudinal uniformity U1 refers to the ratio of the minimum road surface brightness to the maximum road surface brightness on the lane axis. If the bright and dark bands appear on the road surface continuously and repeatedly, that is, the ‘zebra effect’, it will be very annoying for the road users who are traveling in this lane. This problem involves people's psychology, but it also jeopardizes road safety. Vertical uniformity is mainly used to evaluate the size of the ‘zebra effect’.

3, glare
Glare is caused by extreme high brightness or contrast in the field of view, resulting in decreased visual function or discomfort to the eye. Glare in tunnel lighting can come from oncoming vehicle headlights, tunnel lighting, and high brightness outside the tunnel exit. Glare can reduce the ability of people to recognize obstacles and endanger the safety of driving. Tunnel lighting fixtures should adopt a cut-off type, adopting special technical measures to eliminate direct and reflected glare, forming diffuse reflection, so that the light enters the human eye very softly. The International Commission on Illumination uses a relative threshold increment (TI) to account for the decline in visual function due to glare, a measure of disability glare. In the tunnel lighting standard of the European Standards Committee (CR 14380:2003E), the provisions for disability glare are as follows, the tunnel threshold segment and the inner segment during the day and the entire tunnel at night, the relative threshold increment (TI) must be less than 15% .

4, stroboscopic effect
Stroboscopic means that in a long tunnel, due to the discontinuity of the arrangement of the illuminators, the driver is constantly disturbed by the stimulation of light and dark changes. It is related to the brightness change of light and dark, the frequency of light and dark changes, and the total time of stroboscopic. These three are related to the optical characteristics of the luminaire used, the traveling speed of the vehicle, the illuminator installation pitch, and the tunnel length. In general, stroboscopic phenomena caused by stroboscopic frequencies less than 2.5 Hz and greater than 15 Hz are acceptable.

If the vehicle's speed is 60km/h (16.6m/s), the installation spacing of the lights is 4 meters, so the frequency of the strobe is about 4.2Hz. When designing, should consider, choose the appropriate lights installation spacing. If the frequency of the strobe is between 4 Hz and 11 Hz and lasts longer than 20 s, it will cause significant discomfort to the driver.

5, lighting control

The advanced lighting control method is an important skill for reasonable energy saving in the case of ensuring visual conditions and meeting the tunnel lighting requirements. The purpose of lighting control is to change the lighting level of the tunnel at any time. Due to the cloudy, rainy or dusk time, the brightness outside the tunnel is much darker than usual. Therefore, appropriate measures should be taken to reduce the level of illumination in the entrance section to reduce unnecessary energy waste. In the tunnel lighting, the illumination of the tunnel lighting environment or the opening and closing of the lamp can be adjusted and controlled by various dimming devices or control devices according to factors such as daytime, nighttime and traffic volume. At present, most of the foreign countries use photosensitive devices and dimmable electronic rectifiers to form an intelligent lighting system, which reduces the overall brightness of the lights in the tunnel and reduces the energy consumption. At the same time, the uniformity of the tunnel brightness is guaranteed.

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