LED why the rise in tunnel lighting applications? These advantages contributed"......

In the vast majority of outdoor lighting applications, LED has proved its advantages. For tunnel applications, integrated in solid-state lighting devices in particular, point source. In this paper, Lumileds global marketing and business development manager DALE KANE about the specific challenges brought by the tunnel, and how to use LED and lens combination to solve harsh lighting requirements.

"Darkness" and "dark" these two words to a proper extent describes many of the world's highway tunnel illumination. So when you see a bright tunnel, no shadows or black spots, you might want to know why all the tunnels are not so good lighting conditions. In fact, the new tunnel in many parts of the world have shown that LED tunnel lighting carefully designed to help the driver can easily and quickly adjust the visual acuity, the maintenance to a minimum and save energy in improving the light quality at the same time.

We will discuss some of the projects, proof of tunnel based on LED solid state lighting (SSL) value. Tunnel lighting should upgrade by LED, there are two main factors. Municipal Quality usually focus on the life cycle cost and light.

The overall cost of ownership of public lighting depends on several illumination, power consumption, equipment costs, installation costs, maintenance costs, lamp size and lamp life expectancy etc.. Although other factors can be quantified can be considered, but mainly the decision of the competent department of.

Solid state lighting with high quality lighting

With the solid-state lighting technology, the quality of the lighting is very good for use in the tunnel. Compared with the commonly used outdoor lighting products, LED lighting has excellent color.

Road users and pedestrians attach great importance to quality. Some city and public institutions have chosen LED lighting to improve the commercial area, making it more attractive, increasing the sense of security and comfort.

In the tunnel lighting, it can be said that the total cost and visual perception are factors that have. However, considering the status of public funds, we must achieve the total life cycle cost is low. Fortunately, the development of LED technology reduces the LED tunnel lighting system and power purchase cost, and high pressure gas discharge light source (HID) compared with the traditional LED, greatly reduce the life cycle cost and other advantages but also has a solid state lighting system.

Comparison of LED and traditional lighting

At present, the traditional high pressure gas discharge lamp (HID), such as high pressure sodium (HPS) and metal halide lamps (MH), is still the main tunnel lighting. Minimum illumination lighting scheme of tunnel needs higher, to provide security for the users of the environment. The lamp must be able to quite far from the distance from the plane to provide a high level of illumination. A typical installation of highway tunnel is 5-7 meters high, providing clearance for high side vehicle.

High pressure sodium lamp and metal halide lamp for tunnel lighting project designers very attractive, not only provides a low unit cost, and provides high illumination. An array of high pressure sodium lamp and metal halide lamps, each lamp power is usually up to 400W, to meet the requirements of illumination.

However, high pressure sodium (HPS) (Figure 1) and metal halide lamps (MH) are obviously. The two lamps consume a lot of energy, usually light quality is low, can not provide uniform lighting in the tunnel, and if failure occurs, the need for expensive remedial maintenance program. Now, with the development of LED technology, the tunnel operators have a new choice, from the angle of operation and the public more and more attractive.

Figure 1. high-pressure sodium lamp (HPS) tunnel lighting cannot provide consistent illumination level, the poor quality of light.

Based on the most obvious advantage of the LED tunnel lamp is their high efficiency and long service life:

In the typical application of tunnel lighting, LED lighting system can provide high quality >100 LM / W. Because LED is the direction of point light source, the light output can be accurately transmitted to the desired area, compared with the HID system, the system provides additional functions.

LED is a semiconductor device very reliable, long service life, greatly reduces the cost of maintenance and service.

Lighting environment

The benefits of LED lighting in highway tunnel is mainly divided into two categories: the light quality and reduce the impact of traffic flow. LED lamp light quality is largely due to excellent color LED. For example, Lumileds Luxeon T LED CRI super efficient minimum is 70, the common CRI high pressure sodium lamp is 20. When comparing these two techniques, the LED solution will produce a more natural environment based on.

Display color of the spectrum can help drivers better distinguish distant objects more real, than the high-pressure sodium lamp light orange brown better. Even if the absolute luminance level under the same environment, will also feel safer and more comfortable.

Uniform illumination of the entire tunnel is another advantage of LED scheme. By using the optical lens design of advanced mold development, on the road to provide a uniform pattern of light, neither blocked it without interference of glare. This consistency can be achieved, because the LED lamp is a light source array by small but powerful, can according to the needs of the beamforming pattern, such as the use of total internal reflection on each LED (TIR) lens to form the desired beam. In the whole space, it will form a more smooth, more consistent in road lighting, no black or bright spot on the surface.

Entrance lighting and exit lighting

LED tunnel lamp can also enhance light control in the transition of entrance and exit area, let the eyes of the driver can adapt to. The level of illumination lighting simulation design of high pressure sodium lamp and metal halide lamps when traditional in the day according to the external light level, close the lamp part or a whole section (Figure 2).

Figure two. In order to achieve the desired level of tunnel entrance light, high pressure sodium lamp and metal halide lamps are usually too bright, and LED lamp dimming accurately to reach the level of.

If it is to match the tunnel illumination level high pressure gas discharge lamp, there will be a day in most of the time over bright, far from the desired level of illumination. The main reason is that the HID light can not be accurately controlled. On the contrary, LED is fully adjustable light, can accurately match lighting level required, so as to eliminate excessive lighting, reduce energy consumption.

Because LED is very durable, usually do not like HPS or MH lamp as failure, so there is no need to shut down part of tunnel, erecting high-rise platform, maintain a smooth road. (compiled: LED James)

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