In recent years, LED (Light Emitting Diode) technology has made rapid progress. As a new type of light source, LED has many advantages such as long life, high luminous efficiency, low power consumption, good dimming performance, high color rendering index, no fear of vibration, good directionality, low working voltage, environmental protection, and great development potential. It has become an energy-saving light source option for highway lighting, and has been installed and used in many highways in China. There are many failure cases, but there are also successful cases, and the initial investment in successful cases is relatively large due to factors such as the price of LED materials. Under the guidance of the national energy conservation and consumption reduction policy, the application of LED lighting in the expressway has also entered a new development period. Is LED lighting suitable for the future development of the highway?
1 Advantages of high power LED
(1) Energy saving
The former design of the Qianyiping Tunnel of Shaanxi Wuzi Expressway was designed with high-pressure sodium lamps. The box was changed to 315kVA. After the actual use, the LEDs were changed to 80kVA, and the actual power was only 60kW. In actual use, the lighting effect reached the design requirements. Compared with high-pressure sodium lamps, LED lighting can save about 70%.
(2) long life
The LED is a semiconductor that has a lifetime of 50,000 hours when the luminous flux is attenuated to 80% under good heat dissipation. The life of the metal halide lamp is about 12,000 hours, and the life of the high pressure sodium lamp is about 20,000 hours. An important propaganda point for distributors to introduce LED lighting is that it is maintenance-free for 10 years, showing the long life of LED lighting. The long life of LED can effectively reduce the maintenance work of lamps and reduce operating costs.
(3) good color rendering
LED light source output white light, moderate color temperature, 5000K ~ 6000K, compared with high pressure sodium lamp, light color is more natural, color rendering is much better than high pressure sodium lamp, high color sodium lamp color rendering index is only about 20, and white LED can reach 65 ~80. The high color rendering of LEDs undoubtedly helps drivers and pedestrians identify targets and provide better access conditions at the same road surface brightness.
(4) The direction of the light source is good
High-pressure sodium lamp or metal halide lamp is a light source for full-space illumination. It is necessary to change the light emitted by one half space into the other half space by changing the direction of the reflector by 180°. The absorption of light by the reflector and the blocking of the light source itself are inevitable. The efficiency of the lamps is generally only about 70%. Different from the traditional light source, the LED is directional light. The light source of the LED is composed of a very large number of LEDs. By designing the projection direction of each LED, the illuminated road surface can obtain uniform illumination, and the utilization of light is much higher than that of the conventional light source.
2 Constraints
Although LED has many advantages, in actual operation, there are still some constraints in the application of LED light source at this stage. It is these reasons that hinder the development of LED on the highway to some extent.
(1) fever problem
Improving the heating of LEDs is the key to capturing high-power lighting. The working state and heat dissipation design of the LED are not only directly related to the actual luminous efficiency of the LED, but also related to the actual service life. The commonly used LED chip light efficiency refers to the chip light effect when the junction temperature is 25 °C. Due to the heat dissipation design and the ambient temperature, the junction temperature tends to be much higher than 25 °C in actual use, resulting in a large light effect. decline. For example, a chip with a junction temperature of 25 ° C and 100 lm/W may be only 60 to 70 lm/W in actual use.
A technology company in Taiwan invented the loop heat pipe (LHP) cooling technology to replace the commonly used heat sink cooling technology, which has solved this problem well and greatly improved the service life of LED lamps. After 3 years of actual testing, it shows that the light decay is less than 3% after working for 12 hours every day. It is estimated that after 10 years of work, its light decay is only 20%. This basically solves the problem of life.
(2) cost performance problem
Since the price of LED chips is still at a high level, the price of LED street lamps is still higher than that of conventional lamps. The actual data of a municipal road in Shanghai is shown in Table 1.
Through the above comparison, it can be found that the current cost performance of the LED light source is still at a low level. But LED is a semiconductor component. With the rapid development of electronic technology, technology is more and more advanced, and the price will become lower and lower. As an emerging light source, LED is in the stage of rapid development. At present, the luminous efficacy of high-power white LED has reached 150lm/W. Through the study of its luminescence mechanism, it is estimated that the theoretical light effect of LED can reach 350lm/W, which is very large. Development space and potential.
(3) There is no uniform standard
At present, there is no unified national standard for the production of LED light sources. Each manufacturer produces its own products according to its own standards, which is difficult to be universal. The structural design of the LED light source luminaires is an integrated design, that is, the related components cannot be replaced in the field. Whether the LED light source is damaged or the power supply is faulty, the whole lamp must be removed and replaced when there is a problem, and the maintenance work cost is greatly increased. The upgrade of LED products is very fast, and the interface has no national standard constraints. With the update of the chip, it is difficult for manufacturers to guarantee the production of existing products after several years. At that time, the maintenance of the products including the maintenance will become a difficult problem in the operation and maintenance department, and the phenomenon of a street lamp will appear.
3 Conclusion
In recent years, under the call of the national energy conservation and emission reduction policy, there are many successful experiences in the domestic highway lighting, and there are also lessons of failure.
Before the unified national standards for LEDs were developed, the LED industry was mixed, and everyone grabbed the market. However, because the current core technology and supply of LED chips are in foreign countries, the domestic process is not completely processed, and the technology is not packaged. In the case of adequate reliability testing, it is irresponsible to rush to bring products to market, and some highways and municipal roads have unfortunately tested mice. However, due to the significant advantages of LED light sources and the maturity of white LED technology, energy-saving, long-life, uniform illumination, flexible and convenient, green and environmentally friendly semiconductor light source in the highway lighting system, to save construction funds, reduce the use of It is of great significance to contradict the electricity, reduce the maintenance work after the completion of the construction, and build a conservation-oriented society. It is believed that LED light sources have broad application prospects on the expressway.
Edit: Cedar
We can provide hardware design services for customers. After the adoption of the feasibility plan.We can complete the design of Circuit Board Layout, and export the gerber file, BOM and so on. And then start customizing the Printed Circuit Board and PCBA for the customer's product.
Our design software: Altium Designer/ Genesis/ Eagle/ P-cad/ Protel-99SE/ CAM350/ Power PCB /AutoCAD and etc.
PCB Design,Electronic PCB Design,One-Stop PCB Design,Electronic Development PCB Design
Orilind Limited Company , https://www.orilind.com