The application of LEDs (light-emitting diodes) can be said to be everywhere. As a kind of semiconductor luminescent material, compared with other luminescent materials, LEDs are eclipsed by other green materials because of their advantages of green, high efficiency, reliability and durability. As the cost of high-power LEDs continues to decrease, it is possible to gradually replace traditional lamps. The application of LED light source in road lighting has become a hot spot in the semiconductor lighting industry in recent years. What are the special requirements for technology when LED device products are applied to street lamps? What are the advantages of LED street lights compared to current street lights? What are the shortcomings? How to solve? Industry experts have explained from different sides.
The development of national standards is a powerful means of popularization and promotion. LED as a street lamp mainly has the following advantages or features: high luminous efficiency, low reflection loss of lamps, saving energy by 70%; with digital control of brightness function, more power saving; no need for high voltage, high security; The matching software can remotely and automatically control the brightness; provide high-brightness and high-color illumination light source under special circumstances such as accident, fog, rain, etc.; easy installation and maintenance; module installation, no unnecessary wiring; no light pollution or waste; Long life means no need to change frequently, which reduces the potential for traffic disruptions and reduces the maintenance costs paid for this. It has been calculated that the use of LED street lights is superior to high-pressure sodium lamps in terms of laying cost, power consumption cost and life in addition to the cost of single lamps and the cost of initial installations compared to high-pressure sodium lamps.
The main technical problems faced by LED street lamps are: output power and luminous flux, secondary optical design, thermal design and power system design. The improvement of output power and luminous flux also needs to be further improved from the basic level of high-power white LED epitaxial technology and chip technology. In terms of secondary optical design, the radiation forms of LEDs are Lambertian, side-fire, batwing and concentrating. In the field of road lighting, according to the design experience, Lambertian and batwing are more suitable. Through the secondary optical design, the illumination range and luminosity curve of LED meet the requirements of road lighting. Heat dissipation is one of the key problems that LED street lamps need to solve. Because LED street lamps have high brightness requirements and large heat generation, and outdoor use environment is harsh, if the heat dissipation is not good, it will directly lead to rapid aging of LEDs, and the stability will be reduced. The heat dissipation of the LED itself is good. Because the street lamp has the characteristics of outdoor nighttime use, the heat dissipation surface is located on the side to facilitate the natural convection heat dissipation of the air. The power system of LED street lamps is also different from traditional light sources. The combination of low energy consumption, low operating voltage and low output power and low output voltage of solar modules is very suitable. How to make a group of LEDs tightly compressed together safe, Reliable work is also an indicator of LED street lights.
Based on the above analysis of the market prospects and technical issues of LED street lamps, it can be seen that the factors affecting their application are:
First, the high cost of LED street lights is not conducive to popularization. Although the heat dissipation problem of LED street lamps has been initially solved, the excessive price and overweight lamp heads still hinder the popularity of LED street lamps.
Second, the reliability of the modularization of LED street lamps still needs to be strengthened, and LED street lamps may be ineffective due to driving circuits and the like.
Third, LED street lights, whether single-point or multi-point light sources, have the problem of heat dissipation. As for the street lamp with 250W high-pressure sodium lamp, due to the mature technology, the heat dissipation is very good. Even if it works for 5,000 hours, the light decay is still small, and the luminous efficiency can reach more than 70%. With the current technology, high-power LED street lamps under the same conditions are difficult to solve due to heat dissipation problems, and the light decay is large, and the luminous efficiency will drop to 30%. If you want to increase the light efficiency by increasing the voltage and current, it is easy to cause LED chips. The phenomenon of damage.
Fourth, LED street lights have a short range, so LED street lights need to further strengthen research on how to work at higher altitudes. In addition, the development of national LED road lighting standards is also a very powerful means to popularize LED street lights.
The lack of standard specifications can not be fully promoted. LED street lights have two outstanding advantages: energy saving (reported to save more than 50% of electricity), long life (which can reduce maintenance and extend replacement time), so the current development and application of LED street lamps in China fast development. Many large and medium-sized cities have tried some LED street lights, but they have not been used in large quantities.
At present, the main problem of LED street lamps is that there is no standard specification, which cannot be fully promoted. Among them, several main parameters of LED for street lamps such as color temperature, color rendering (color rendering index) and glare have not been determined.
In addition, the price of LED street lamps is too high. At present, depending on the power and installation height, the price is between 3,000 yuan and 5,000 yuan per unit. It is difficult to promote and apply large areas.
The urban management system of street lamps is responsible for the long position, which brings great difficulties to the promotion and application of LED street lamps.
The development of national standards is a powerful means of popularization and promotion. LED as a street lamp mainly has the following advantages or features: high luminous efficiency, low reflection loss of lamps, saving energy by 70%; with digital control of brightness function, more power saving; no need for high voltage, high security; The matching software can remotely and automatically control the brightness; provide high-brightness and high-color illumination light source under special circumstances such as accident, fog, rain, etc.; easy installation and maintenance; module installation, no unnecessary wiring; no light pollution or waste; Long life means no need to change frequently, which reduces the potential for traffic disruptions and reduces the maintenance costs paid for this. It has been calculated that the use of LED street lights is superior to high-pressure sodium lamps in terms of laying cost, power consumption cost and life in addition to the cost of single lamps and the cost of initial installations compared to high-pressure sodium lamps.
The main technical problems faced by LED street lamps are: output power and luminous flux, secondary optical design, thermal design and power system design. The improvement of output power and luminous flux also needs to be further improved from the basic level of high-power white LED epitaxial technology and chip technology. In terms of secondary optical design, the radiation forms of LEDs are Lambertian, side-fire, batwing and concentrating. In the field of road lighting, according to the design experience, Lambertian and batwing are more suitable. Through the secondary optical design, the illumination range and luminosity curve of LED meet the requirements of road lighting. Heat dissipation is one of the key problems that LED street lamps need to solve. Because LED street lamps have high brightness requirements and large heat generation, and outdoor use environment is harsh, if the heat dissipation is not good, it will directly lead to rapid aging of LEDs, and the stability will be reduced. The heat dissipation of the LED itself is good. Because the street lamp has the characteristics of outdoor nighttime use, the heat dissipation surface is located on the side to facilitate the natural convection heat dissipation of the air. The power system of LED street lamps is also different from traditional light sources. The combination of low energy consumption, low operating voltage and low output power and low output voltage of solar modules is very suitable. How to make a group of LEDs tightly compressed together safe, Reliable work is also an indicator of LED street lights.
Based on the above analysis of the market prospects and technical issues of LED street lamps, it can be seen that the factors affecting their application are:
First, the high cost of LED street lights is not conducive to popularization. Although the heat dissipation problem of LED street lamps has been initially solved, the excessive price and overweight lamp heads still hinder the popularity of LED street lamps.
Second, the reliability of the modularization of LED street lamps still needs to be strengthened, and LED street lamps may be ineffective due to driving circuits and the like.
Third, LED street lights, whether single-point or multi-point light sources, have the problem of heat dissipation. As for the street lamp with 250W high-pressure sodium lamp, due to the mature technology, the heat dissipation is very good. Even if it works for 5,000 hours, the light decay is still small, and the luminous efficiency can reach more than 70%. With the current technology, high-power LED street lamps under the same conditions are difficult to solve due to heat dissipation problems, and the light decay is large, and the luminous efficiency will drop to 30%. If you want to increase the light efficiency by increasing the voltage and current, it is easy to cause LED chips. The phenomenon of damage.
Fourth, LED street lights have a short range, so LED street lights need to further strengthen research on how to work at higher altitudes. In addition, the development of national LED road lighting standards is also a very powerful means to popularize LED street lights.
The lack of standard specifications can not be fully promoted. LED street lights have two outstanding advantages: energy saving (reported to save more than 50% of electricity), long life (which can reduce maintenance and extend replacement time), so the current development and application of LED street lamps in China fast development. Many large and medium-sized cities have tried some LED street lights, but they have not been used in large quantities.
At present, the main problem of LED street lamps is that there is no standard specification, which cannot be fully promoted. Among them, several main parameters of LED for street lamps such as color temperature, color rendering (color rendering index) and glare have not been determined.
In addition, the price of LED street lamps is too high. At present, depending on the power and installation height, the price is between 3,000 yuan and 5,000 yuan per unit. It is difficult to promote and apply large areas.
The urban management system of street lamps is responsible for the long position, which brings great difficulties to the promotion and application of LED street lamps.
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