Summary
At present, almost all tunnel lighting uses high-pressure sodium lamps as a light source. However, high-pressure sodium lamps have many shortcomings in radiation form, color rendering, visual sensitivity characteristics, power specifications, brightness control, etc., and the emerging LED tunnel lighting fixtures have overcome their excellent performance, especially the controllability of brightness. Many shortcomings of high-pressure sodium lamps are becoming the mainstream lamps for tunnel lighting in the world today. The author has done some work on energy saving in tunnel lighting. This paper introduces the corresponding energy-saving measures for the factors affecting the energy consumption of tunnel lighting, and analyzes the LED lighting energy-saving scheme accordingly.
First, the influence of the brightness outside the hole on the tunnel lighting energy consumption and energy saving countermeasures
The standard values ​​for enhanced illumination in the tunnel are derived from the brightness outside the tunnel hole multiplied by a factor. Taking the two-lane one-way traffic of 80km/h as an example, if the designed traffic volume is greater than or equal to 2400 vehicles/h, the brightness reduction factor of the inlet section is 0.035.
As can be seen from the above table, the brightness outside the hole has a considerable influence on the energy consumption of the tunnel. The brightness outside the hole is high, and the lighting intensity in the hole is correspondingly increased, and the investment in electrical equipment in the hole is correspondingly increased. Therefore, when designing the lighting inside the tunnel, the designer should first measure the brightness outside the tunnel hole, and then design the inner lighting according to the measured results, so as not only avoiding the waste of electrical equipment investment caused by the excessive redundancy of the lighting design. It can also save a lot of power in the operation process. When constructing the Huangtatao Expressway in Anhui Province, the preliminary design was to design the interior lighting of the cave at a brightness of 4000 cd/m2. In the formal design stage, the designers went to the scene to measure the brightness of the tunnel outside the tunnel, and measured that the brightness outside the tunnel was mostly around 3000 cd/m2. Therefore, the designer designed the lighting system in the hole according to the measured brightness outside the hole. As a result, the total power of the lighting fixture was reduced by 23% compared with the original, and the equipment investment was reduced by about 19%. It can be seen that accurate measurement of the brightness outside the tunnel hole is necessary for rational design of the interior lighting, reducing lighting energy consumption and investment in electrical equipment.
This example shows that the brightness outside the hole has a great impact on the lighting and equipment investment in the cave. Therefore, how to reduce the brightness outside the hole is also a problem that tunnel designers should consider. Generally, the following measures can be taken to reduce the light in the tunnel entrance: one is to plant evergreen trees on both sides of the roadbed; the other is to decorate the hole in dark tones; the third is to make a large area on the slope of the mountain outside the cave. Planting evergreen vegetation and so on. These measures can all play a role in reducing the brightness outside the hole.
Second, the impact of weather outside the tunnel on tunnel lighting energy consumption and energy-saving measures
The brightness outside the hole has a great influence on the energy consumption of the lighting, and the brightness outside the hole is different from the weather, season and time. Taking a tunnel with a brightness of 3000 cd/m2 outside the hole as an example, the maximum brightness at noon outside the hole in the summer solstice is 3000 cd/m2, and the maximum brightness outside the hole in the autumn equinox is about 1860 cd/m2. The maximum brightness outside the hole in the winter solstice is about At 842 cd/m2, the brightness outside the hole in morning, evening and cloudy can be as low as 200 cd/m2 or less. At present, tunnel lighting in China mostly follows four levels of dimming, namely, four brightness levels: sunny, cloudy, cloudy and heavy cloudy. Most of these four brightness levels are not divided into seasons and morning, noon and afternoon, so the waste of energy consumption is still quite large. Figure 1 shows the enhanced lighting power line and actual power demand curve in a sunny day hole of a high pressure sodium lamp. Figure 2 shows the enhanced lighting power line in the LED lamp cavity. Figure 3 shows the enhanced illumination power curve of the tunnel LED brightness intelligent stepless control system to track the brightness outside the sunny hole. It is also the actual LED lamp power demand curve. The area under the lower line is the total energy consumption for the daylighting of the luminaire. The top one in the figure is the sunny day lighting power line of high-pressure sodium lamp. The percentage of energy consumption indicated is the comparison with the natural lighting energy consumption of sodium lamp.
figure 1
It can be seen from Figure 1 that the area under the summer light of the sodium lamp to enhance the lighting power demand curve (ie, energy consumption, the same below) only accounts for 37% of the area under the design lighting power line, while the area of ​​the lower part of the annual average daytime sodium lamp power demand curve is only It accounts for 22.7% of the area under the design lighting power line. If the output power of the sodium lamp is controllable over a wide range, then only the daily illumination power line is used for tracking control. For enhanced lighting, energy saving is 77.3% per year. The goal of realizing the real-time change of brightness outside the tunnel in the tunnel illumination hole has been pursued by human beings for more than a century. However, due to the limitations of traditional light sources, humans have not been able to do so. Incandescent lamps can be steplessly dimmed, but their dimming makes them meaningless due to their low light efficiency. Gas discharge lamps, such as high pressure sodium lamps, are currently only dimmable in a small range. This dimming has little effect on the energy consumption of tunnel lighting during the day. For high-pressure sodium lamps, a better energy-saving method is to use a multi-loop grading control method to adjust the inner loop of the hole according to the detected brightness outside the hole. This method of hierarchically controlling the brightness of the hole produces a better energy saving effect. However, with the development of science and technology, LED is becoming the mainstream light source in the field of lighting with its excellent performance. At present, the LED light effect that can be supplied in large quantities has reached 90lm/W, and the brightness is constantly improving, and the control method is more advanced.
Figure 2 shows the enhanced lighting power line in the LED lamp cavity. As can be seen from the figure, the power line of LED sunny lighting is only 50% of the high pressure sodium lamp, which is mainly because the LED tunnel lamp has higher lamp efficiency, maintenance coefficient, color rendering index, effective illumination and arbitrarily set power. The characteristics of the specifications, such that it meets the requirements of the specification, the energy consumption is greatly reduced. Therefore, the simple replacement of high-pressure sodium lamps with LED tunnel lights can achieve a 50% energy saving goal.
figure 2
The LED light source is different from other light sources, and its operating current can be large or small within the rated range. This feature lays the foundation for LED lamp to achieve stepless brightness control. At present, the tunnel LED brightness intelligent stepless control system has been successfully developed, and its promotion and application will definitely have a significant impact on road tunnel lighting energy saving.
image 3
Third, tunnel LED lighting brightness intelligent stepless control system energy saving analysis
Figure 3 depicts the enhanced illumination power curve tracked using the tunnel LE D illumination brightness intelligent stepless control system. As can be seen from the figure, the annual average lighting power demand is smaller than the summer solstice, and the winter solstice power is the lowest. With the tunnel LE D illumination brightness intelligent stepless control system, no matter which day of the year, it will be illuminated according to the actual power demand, without having to pay more for lighting energy. It can be calculated that the annual average daytime lighting energy consumption is much lower than that of the sodium lamp source tunnel illumination and the constant brightness LED tunnel illumination, which is about 16.5% of the sodium lamp and 33% of the LED lamp, realizing the true meaning. Need to be illuminated. The system is used for tunnel lighting, and the relative energy savings is not much different regardless of the weather. It can replace the enhanced lighting of high-pressure sodium lamps, achieving 83.5% energy-saving goals, and saving 67% energy than LED tunnel lights with uncontrollable brightness. Therefore, the energy saving effect of this system is quite remarkable. It will be an ideal solution for energy saving in tunnel lighting for a long time now and for a long time.
Fourth, the impact of road and wall materials on tunnel lighting energy consumption.
The reflectivity of the asphalt pavement is lower than that of the cement pavement. In the lighting design, the illuminance of the asphalt pavement must be 30% higher than that of the cement concrete pavement, so that the road surface brightness of the two pavements is basically the same. Therefore, from the perspective of reducing energy consumption and investment in electrical equipment, cement concrete pavement should be used as much as possible in the design stage. In the "Code for Design of Ventilation Lighting for Road Tunnels", the average brightness of the 2m high wall of the left and right sides of the road surface should not be lower than the average brightness of the road surface. Therefore, it is also possible to save 1 to 3 percentage points of energy by coating a white paint with a high reflectance on the wall.
5. The impact of lamp power specifications on tunnel lighting energy consumption.
The standard values ​​for tunnel lighting are specified in industry standards. If the illumination greatly exceeds industry standards, the energy consumption will also be too high. Since the power specifications of the high-pressure sodium lamp source are usually only 75W, 100W, 150W, 250W and 400W, when the road needs 110W or 180W illumination, since there is no corresponding power source, only 150W and 250W specifications are adopted. This choice inevitably increases lighting energy consumption.
For the LED light source, its power can be designed according to the actual needs of the tunnel, and how much power is actually required to be equipped with much power, thereby eliminating the waste of electric energy caused by excessive illumination (lighting intensity greatly exceeding the specification requirements). For example, 60W for each LED lamp in the basic section is enough. Therefore, when designing the LED lamp, it is designed according to 60W instead of 75W, which avoids the waste of electric energy caused by excessive illumination.
Sixth, the impact of power supply voltage on lighting energy consumption.
The gas discharge lamp has high requirements on the stability of the power supply voltage, and the general variation is within 6%, otherwise the energy consumption will be greatly increased, and the life of the light source is greatly reduced.
In the evening, fluorescent lights, metal halide lamps and high pressure sodium lamps are usually brighter and brighter. Why is this happening? There are two main reasons for this: First, because the power supply voltage in the middle of the night is usually around 220V ~ 230V; and in the second half of the night, the power supply voltage will reach 15% of the rated value, up to 250V, so that the power Increase, brightness increases. Secondly, the gas discharge lamp source has a negative resistance characteristic. When the mains voltage rises, the voltage across the light source will not rise but fall, while the operating current of the light source will increase sharply; this makes the light source and the ballast The power consumption of the device has increased significantly. For example, a 150W high-pressure sodium lamp will increase to 300W including ballast power when operating at 250V. At this voltage, the life of the sodium lamp is greatly reduced, almost less than 30% of the rated life. This is the main reason why the actual power consumption of the sodium lamp is far beyond the rated power consumption when it is used for the street lamp, and it is also the reason why it is brighter and brighter.
LED lamps do not require high power supply voltages, generally between 170 and 250V. Good LED lamps are mostly powered by constant current. The current flowing through the LED is not affected by the change of the power supply voltage, but only depends on the factory setting, so its output power is almost constant; with brightness control The operating current of the functional LED luminaire also depends on the control signal, which can adjust the illumination intensity in real time according to the lighting needs of the actual application site to achieve the desired energy saving effect. In terms of basic lighting, if LED light source is used, the energy consumption of the second half of the night can be reduced by half by advanced dimming technology, so that the energy consumption of the LED light source can be reduced by 25% on the basis of the original energy saving. Up to 75%.
Due to the wide operating voltage range of LED luminaires, it is permissible to use cables with thinner diameters when designing the line without turning off or starting. Therefore, the use of LED light source can save a lot of cable costs, and the comprehensive energy saving rate is more than 80% per year under the condition of comprehensive investment and sodium lamp.
7. Influence of harmonics and power factors on power consumption
The power supply mode of the LED light source is a DC constant current power supply mode. Therefore, LED lamps must be equipped with a constant current drive power supply. At present, the constant current sources used in LED lighting fixtures are switching power supplies, that is, switching LED constant current driving power sources. Since the switching power supply is a rectifying load, it will cause serious harmonic pollution to the power grid when used in a large amount.
In the tunnel lighting system, the harmonic hazard mainly has the following aspects: 1. The waveform distortion of the grid voltage is caused; 2. The cable line is overheated, the insulation aging is accelerated, the damage is easy, and the short circuit between the lines and the ground fault cause electrical fire and personal injury. Electric shock accidents, especially neutral overload, heat, and even burning; 3. Transformer overheating, damage and even burning; 4. Capacitor with compensation power factor is overheated, easy to damage, and life is greatly shortened; 5. Power factor of the system The reduction causes the loss of the power supply system to increase; 6. The electrical protection components such as the circuit breaker and the leakage protection device, the contactor, and the thermal relay are overheated, malfunctioning, malfunctioning, and the grounding protection device is malfunctioning; 7. wasting system capacity and reducing the function of the protection device.
To solve the tunnel lighting harmonic hazard, the following two methods can be used: 1. Improve the capacity and quality of the transformer, increase the cross-sectional area of ​​the cable, especially increase the cross section of the neutral cable, and increase the capacity of other electrical equipment. However, this method cannot fundamentally eliminate harmonics, but will increase investment in electrical equipment and reduce protection characteristics and functions. 2. Improve the power factor of the LED tunnel light drive power supply. Power factor requirements should be addressed when selecting LED tunnel lighting fixtures. Generally, the power factor needs to be above 0.8, which requires the LED constant current driving power supply to have a power factor correction circuit. A good performance LED driver power supply with a power factor of 0.95 or higher. If such a power source is selected, it will be the best solution to eliminate harmonic hazards.
Conclusion
Tunnel lighting electricity costs are an important part of highway operating costs. A one-way traffic tunnel with a length of 400m, if using high-pressure sodium lamps to light according to the standard requirements, the annual lighting power consumption in the tunnel is about 600,000 yuan. In tunnel lighting, the illumination at the exit and entrance of the tunnel is dozens of times the basic illumination of the tunnel. Due to the high operating costs, many operators are overwhelmed and have to reduce lighting standards to reduce operating costs. This practice will also create frequent accidents for tunnel operations. Therefore, how to reduce the energy consumption of tunnel lighting, especially the energy consumption of the entrance, is an urgent problem for all highway operators with tunnels. At present, the total mileage of highway tunnels in China is close to 2,000 kilometers, and the total lighting energy consumption is quite large. This paper aims to introduce some energy-saving methods for tunnel lighting to help the peers to minimize the energy consumption of tunnel lighting and save huge operating expenses. It provides a feasible method for achieving sustainable development of the national economy, protecting the environment and reducing CO2 emissions.
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