Analysis of LED Low-altitude Lighting Application of Qingdao Bay Bridge

I. Introduction to the Qingdao Bay Bridge Project

Qingdao Bay Bridge is the starting point of the national highway network Qingdao-Lanzhou expressway. It is an important part of the main frame of the “five vertical, four horizontal and one ring” road network in Shandong Province, and it is also the cross-sea passage of the east and west coast of Jiaozhou Bay planned by Qingdao. "One bridge" in one road, one bridge, one tunnel. The first phase of the Qingdao Bay Bridge starts from 200 meters north of the Licun River Bridge on Qingdao’s Side Ring Bay Road. It is 1 km east of the Jiaozhou Bay Expressway on the Huangdao side, and the design start point of the Jiqing South Line is followed. The Red Island Interchange is set up in the middle. The red island connection line is connected. The main line has a total length of 28.047 kilometers, including 25.171 kilometers of the sea-crossing bridge, 749 meters of Qingdao side wiring, and 1.3 kilometers of yellow island side wiring. The main line bridge is 35 meters wide and has six lanes in both directions. The design speed is 80 km/h.

After the completion of the Qingdao Bay Bridge, it will become one of the landmarks and important attractions of the island city. In order to ensure the safety of driving at night and to show the unique charm of the Bay Bridge at night, it is necessary to carry out an aesthetic design lighting design for the bridge. To this end, not only need to care about the needs of bridge traffic safety, but also need to care about the interaction between the bridge and the surrounding environment, and care about the symbolic significance of the bridge. The night illumination of the Bay Bridge should be both functional and landscape-oriented. Combine the two to achieve a comfortable and safe lighting effect, and realize the organic unity of the bridge traffic function and the landscape function.

Second, lighting design requirements

The Qingdao Bay Bridge is located in the bay. The natural environment is complex and the climate is harsh. Its lighting scheme must be based on the full familiarity and understanding of the local geography and climate. According to the technical specifications of the highway and bridge, the operational requirements and natural conditions of the bridge are combined. And design. In addition to the need to design energy conservation, environmental protection and intelligence, we also need to fully consider the landscape effect. Its design requirements are as follows:

1, in line with the lighting function requirements

The lighting of the bridge directly affects the driving safety of the vehicle. In the lighting design, certain brightness and uniformity must be ensured, so that the driver can clearly distinguish the road traffic situation and traffic signs without feeling the eye fatigue and glare. Control is especially important to ensure traffic safety. Since the sea surface tends to have large humidity, foggy days and low visibility, it is also necessary to consider the fog permeability and inductivity of the light source. At the same time, the choice of brightness should comply with the relevant regulations of night lighting, and suppress light pollution.

2, high reliability

The Qingdao Bay Bridge has a long distance and its environment is characterized by high salt spray, thunderstorms and typhoons. Therefore, the selection and installation of the luminaire should fully consider the factors of earthquake resistance, wind resistance, corrosion resistance and easy maintenance. The system equipment should have multiple protections to resist inductive lightning strikes and grid surges, waterproof gas intrusion and salt spray corrosion; in the case of individual equipment failure, the system can still operate stably without affecting or affecting the lighting system's on-time opening and closing. . The single lamp can be self-regulating, which can overcome the influence of grid and long-distance power supply voltage fluctuations on road lighting and facilities, and prolong the life of the light source.

3, environmental protection and power saving

In order to meet the lighting requirements, a larger number of lamps need to be installed, which brings about a huge power consumption. To this end, energy-saving lamps should be selected as much as possible in order to meet the lighting function requirements. The street lamp control system is used to control the switch state and illumination control of the street lamp according to the traffic volume and environmental conditions to reduce the power load of the lighting system.

4, enhance the bridge aesthetics

The overall lighting effect is to create a good night image of the building, and its lamp position can not destroy the daytime image of the building. As part of the landscape, bridge lighting needs to be ornamental and decorative. The lighting design should grasp the architect's design style and intention, and without changing the original style, structure and layout of the bridge, make it glow different from the daytime at night, and structure and decoration details of the key parts of the building. The display is more vivid and magnificent.

Third, the bridge lighting technical parameters

Qingdao Bay Bridge is an important traffic artery connecting Qingdao, Hongdao and Huangdao. The speed is fast and the flow is large. The lighting requirements of the whole bridge are very high. Since the current national standards for LED low-altitude lighting are not implemented, refer to the International Commission on Illumination CIE. The seven technical parameters of the bridge lighting quality provided are: bridge deck average illumination, bridge deck uniformity, glare threshold increment, lamp temperature rise, lamp life, IP rating, LED particle efficacy.

Fourth, the actual comparison of LED and HID sodium lamps

1. Advantages and disadvantages of LED low-altitude lighting and high-pressure sodium lamp high-pole lighting:

At present, the main bridge is a high-sodium sodium light source. See the following picture for details:

China's currently built Gulf Bridges such as the Hangzhou Bay Bridge and the Donghai Bridge all use light poles and high-pressure sodium light as the main lighting. The Qingdao Bay Bridge will use LED low-altitude lighting as the illumination. The advantages and disadvantages of the two are as follows:

● The color of the high-pressure sodium lamp is yellow, the color temperature and the imaging index are relatively low, and the imaging index is only about 25 (yellow).

The color temperature of the LED light source can be flexibly selected between 400 and 7000K, the imaging index can reach 80 or more, and the visual effect is closer to natural light.

● The lamp structure of the sodium lamp determines the light source utilization of the lamp is low, only about 70%. The angle of illumination of the tube is 360°, and most of it must be reflected by the reflector to reach the designated area.

The light source utilization rate of the LED lamp is high, about 90%. The illumination angle of the LED diode can be kept consistent with the illumination angle of the lamp, and the directivity is strong. Therefore, most of the light of the lamp is directly irradiated to the designated area, and the light source utilization rate is high.

● High-pressure sodium lamp bulbs have a long startup time, causing voltage fluctuations during startup, which is polluted to the power grid. It is necessary to have a certain time interval when starting up again. The high-pressure sodium lamp can reach normal brightness for about 5 to 10 minutes, and the time interval for restarting is generally greater than 5 minutes.

LED lights do not have a startup delay problem, DC drive, no pollution to the grid. It can be turned on instantly and can work at any time, which can realize intelligent energy-saving control very conveniently.

● The temperature of the sodium lamp is very different when the lamp is on and the lamp is off. If the lamp body does not have a respiratory system, the reflector is easily corroded by harmful gases and generates a large loss of light.

The LED luminaire does not need to be equipped with a breathing system. The design can solve the heat dissipation problem well. The general power used on the bridge is 4 W to 10 W. The heat dissipation effect of the luminaire is good. Around 30 °C.

● From the glare threshold, the glare threshold of high-altitude street lights is generally between 9 and 15, while the glare threshold of low-altitude LED illumination can be controlled between 1 and 5, which has low impact on drivers and passengers.

● The life of sodium lamp is generally about 20,000 hours (GE NG400T/E40 nominal life is 24,000 hours), and it can be used with ballasts, triggers and capacitors, which will be less than 20,000 hours (in practical applications, it rarely reaches 20,000 hours of life).

LED light source life can reach 30,000 to 50,000 hours (CREE R2 chip nominal life of 50,000 hours), the driving life is generally 30,000 to 50,000 hours, with the use of lamps with very good heat dissipation (bridge low-altitude lighting power Both are between 4W and 10W), and the life expectancy will reach 30,000 hours or more.

In summary, LED lamps have a great advantage over sodium lamps in terms of power consumption, which is more in line with the current low carbon, energy saving, environmental protection and ecological policies advocated by the state. Low-altitude LED lamps are still in the stage of R&D and start-up, and the cost of construction is relatively high. At present, there is no specific practical case for functional lighting on extra-large bridge projects, which has certain risks.

Five, Led guardrail lights low-altitude lighting practice

Although low-altitude LED guardrail lights have not been applied on a large scale, according to the data, LED low-altitude guardrail lighting is currently being used in many places in the country. The following are examples:

In the distance is a high-pressure sodium lamp, and the color rendering index is significantly worse than that of LED. Fence tube LED lighting effect real image. It can be seen from the photo of the following photos that LED low-altitude lighting can fully meet the actual illumination requirements, and the uniformity of illumination is better, and the color rendering is also better than that of high-pressure sodium lamps.

Six, LED low-altitude lighting design points on the Qingdao Bridge

According to Table 1, the main design points of the luminaire are as follows:

Average illumination: According to Table 1, CIE stipulates that the illumination range of outdoor traffic area is 20 to 30lx, and the uniformity of illumination is generally controlled within 0.3~0.4 to meet the requirements of vehicle driving, and participate in the LED guardrail lamp test of Qingdao Bay Bridge. The uniformity of some of the segments can reach 0.6 or higher, which can basically meet the needs of TV broadcast.

Glare Limitation: Glare caused by high-intensity illuminants appearing in the observer's field of view is direct glare. In the eyes of the observer, direct glare generally comes from the range of 0 ° ~ 45 ° angle of the visual axis, especially 0 ° ~ 20 ° (as shown in Figure 1 below).

Take the guardrail luminaire as an example. In Figure 1, because the light pole is not used, the human eye cannot see the luminaire above 45°. Therefore, if the luminaire is designed to limit the glare to a negative angle below 0°, it will be perfect. To solve the problem of glare, the following are the solutions that some manufacturers actually use:

Glare threshold:

The threshold increment TI is used to measure disability glare. Disability glare can cause a decrease in visibility. This is because the light from the glare source scatters in the direction of the retina, forming a bright light curtain that is superimposed on the original clear scene, thereby increasing the background brightness and reducing the contrast. This light curtain can be measured by an equivalent light curtain brightness Lv. The magnitude of the threshold increment depends on the brightness of the light curtain and the adaptation brightness Lav of the eye. Its calculation formula is:

In the formula:
K—age coefficient, generally 10, suitable for observers of 23 years old Lav—average brightness of road surface (cd/m2)
Eeyei - the illumination of the human eye retina by the i-th light source in the direction of the vertical line of sight (lx)

Description:
1. The luminaire is mounted on the guardrail at a height of 1.2 m
2. The total height of the guardrail is 1.4 m
3. The rectangular line in the figure is a car, and the height of the person in the car is about 1. 3 m. 4. As shown in the figure, the installation height of the human eye in the car is more than 10 cm, which means that the light of the lamp is out. The mouth is below the human eye (-5 ° angle), and no direct light from the luminaire is injected into the human eye. This is a very good solution to the glare problem of the luminaire. 5. This scheme has very high requirements for the light distribution of the luminaire. The light exit must be between the red lines. 6. Several manufacturers involved in the test section have used this method to solve the glare problem, and the actual effect is good.

Θ—the angle between the line of sight and the direction of the ith glare source incident on the observer's eye ray (°)

N—the total number of glare sources

It can be seen from the formula that the glare threshold increment is mainly for the street lamp, because it has the illuminance of the light source in the vertical line of sight direction, and the low-altitude lighting fixture is installed below the human eye (as shown in Figure 2), so the glare The threshold increment is no longer applicable here. That is to say, with low-altitude illumination, the glare threshold is essentially zero, with little impact on the driver's line of sight.

Lamp temperature rise:

Since the lamps are all low-power lighting, the maximum is 10 watts, the lighting design is reasonable, and the temperature rise of the lamps is 30 °C, which has no effect.

Lamp life:

The CREE chip is used, and the high reliability matching power supply is selected. The overall service life of the lamp is expected to be more than 30,000 hours.

Light effect of the luminaire:

Since the chip with a luminous efficacy above 110Lm is specified, the luminaire basically adopts the reflection mode of the convex mirror. The loss rate is generally above 80% for the HID source, and the effective luminous efficiency is above 90Lm.

Seven, LED low-altitude lighting problems and prospects

LED is a light-emitting diode lighting product produced by semiconductor as a raw material and high-tech computer chip. It enters human life with a filamentless, mercury-free, electronic-free phosphor, purely illuminated green light source, and it is generally illuminated. Compared with green, non-polluting, long life, cold light source, the light source has a life of more than 30,000 hours, a color temperature of about 5000K, close to daylight, and the same illumination can save 50% to 70% energy compared with traditional light sources, no heavy metal emissions, no Ultraviolet and infrared radiation, fully in line with international and domestic lighting industry standards.

Although LED luminaires are still not mature enough, there are always defects of one kind or another, which are relatively expensive. At present, they are still based on national road lighting design standards. In fact, there are some specific standards that do not meet the needs of LEDs, especially low-altitude lighting.

At the beginning of 2009, in order to expand domestic demand, promote the development of China's LED industry, and reduce energy consumption, the Ministry of Science and Technology launched the “Ten Cities and Ten Thousands” semiconductor lighting application demonstration city program, covering 21 cities including Beijing, Shanghai, Shenzhen and Wuhan. The Qingdao Bay Bridge is also actively promoting the country's promotion. For the first time, LED low-altitude lighting is used on such a long bridge. Although there are unknown risks, let us have low-altitude LED lighting in the early preparation and use of the test section. With deeper understanding and confidence, I believe that Qingdao Bay Bridge will be the first large-scale LED low-altitude lighting project to eat "crab".

With the joint efforts of relevant leaders and experts and manufacturers, LED low-altitude lighting will be applied in Qingdao Bay Bridge, and LED light source will become the dominant light source in the 21st century. The application and practice of LED low-altitude lighting in Qingdao Bay Bridge will also provide a new idea and reference for the implementation of other large bridges and urban interchange lighting projects at home and abroad.

references:

Peng Yingzi High/fast road low light lighting application analysis architectural lighting design magazine 2009/10
Ma Jian, “Road Lighting Technology” Zhang Haijun, Institute of Building Technology, Tianjin University, “Comparison of Road Lighting Standards and Requirements for Light Distribution of Lamps”
Wang Wei's "Analysis of the Status Quo of LED Street Lights"
Shi Xiaohong's national standard "Performance Requirements for Road and Street Lighting" mainly introduces Chen Chaozhong's "Road Lighting Technology" GE&CREE sample data

Edit: Sophy