Compared with traditional street lamps,the advantages of LED street lamps
Compared with traditional street lamps represented by high-pressure sodium lamps, LED street lamps have many potential advantages.
1. High luminous efficiency and low energy consumption.
At present, the luminous efficiency of high-power white LED has exceeded 100lm/W, and the laboratory level of high-power white LED by foreign photoelectric semiconductor has reached 160lm/W in early 2009.
According to the us department of energy (DOE), the light efficiency of high-power LED commercial products can reach 165lm/W by the end of 2020, and the light efficiency of laboratory samples can reach 230lm/W.
After 2020, LED light will basically no longer have a big increase, will enter a slow period.
In road lighting, the high pressure sodium lamp is dominant because its light efficiency can reach 120lm/W.
However, with the continuous improvement of LED light efficiency, the monopoly position of high-pressure sodium lamp street lamp is in jeopardy.
At present, the above 150W LED street lamps used in the secondary road have shown obvious advantages in energy conservation.
Traditional street lamps light source generally to the whole space, but need only street lamp illuminates road traffic and pedestrians, so in street lamp lighting design, in order to make the light even as much as possible and projected onto the pavement, you need to use the curved reflector to gather light and make it to the direction of the light you need.
In the process of light transmission, the loss caused by the obstruction of the light source and the absorption of the reflective surface, the luminous efficiency of the street lamp is only 65%~70%.
LED street lamp, because of its good direction, in the use of secondary optical lens, the efficiency of the lamp can reach about 80%.
If three more optical designs are carried out, the luminous efficiency of the luminaire can reach 85%-90%.
2. Long lifespan.
The life of street lamp directly affects the maintenance cost of whole road lighting.
At present, the life of high pressure sodium lamp is about 28000 hours, while the life of high-power LED (chip) is generally between 50 and 70,000 hours.
High - pressure sodium lamp and LED average life definition are different.
High pressure sodium lamp life expectancy is defined as "a group of subjects of light lit up to 50% when the number of damaged sample time", and the LED (chip) refers to the average life expectancy is "a group of subjects the ignited to 50% quantity of droop to 70% of the time".
If the LED is measured by the life definition of the high pressure sodium lamp, the LED (chip) with a life span of 50,000 hours can reach 100,000 hours.
The high pressure sodium lamp, measured by the life definition of the LED, lasts only about 14,000 hours.
Of course, LED life is not the life of LED street lamps.
The life of the LED street light is made up of LED light source joint decision of life and the life of the drive circuit, and the life of the LED and its driver circuit depends on the cooling capacity of lamps and lanterns, circuit topology and the selection of electronic components and a variety of factors are determined.
3. Good color rendering.
Although high pressure sodium lamp has the highest luminous effect in traditional light source, it has the worst color rendering, and the color index Ra is only about 20.
Such poor color rendering can only help people to perceive the road condition, and does not help pedestrians to distinguish clearly.
The color index of LED is about 80, which is basically close to the natural light, which is more realistic and reflects the color of the object itself.
The high visibility of LED will undoubtedly help drivers and pedestrians to identify targets and provide better access conditions under the same pavement brightness.
4. Quick start
Incandescents are light, but the actual start-up time is about 0.1~0.2 seconds.
Gas discharge lamps such as high pressure sodium lamp and metal halide lamp will take tens of seconds or even ten minutes from the start to stable light output. After the shutdown, it will need to wait for 3~6 minutes to cool before starting.
The LED startup time is only a few tens of sodium seconds (ns), and there is no waiting time to restart. The LED lamps can work in a continuous open/closed state.
5. Convenient for optical design.
LED is small in size, can be in half plane on the directional light, the lamps and lanterns design time can be approximated as a point source, very suitable for the use of the lens or reflector for optical design, to obtain ideal light distribution, to achieve higher efficiency of lamps and lanterns.
6. Strong modeling and strong structure.
LED street lamps and lanterns are plastic and flexible. They can be designed to reflect the decorative and local cultural characteristics, and add value of aesthetic and urban imagery.
LED is a solid-state light source with no glass and filament and other vulnerable parts.
LED lamps can be made very firmly in structure by rational design.
7. Low-carbon environment protection, especially suitable for solar photovoltaic technology.
Gas discharge lamps such as high pressure sodium lamps contain mercury and other harmful substances, which can cause long-term serious pollution to the environment and water sources.
LED chips and their packaging can meet the eu RoHS directive, free of harmful substances such as mercury and lead.
LED waste can be recycled, and will not cause pollution to the environment.
The characteristics of LED dc drive are especially suitable for the application of solar pv technology and landscape complementary technology to road lighting, so as to realize the real energy conservation and environmental protection lighting.
8. Have the potential total cost advantage.
At present, the unit price of LED street lamp is more than four times higher than that of high pressure sodium lamp.
The price of a 150W LED street lamp is equivalent to 400W high pressure sodium lamp, but the former price is 6000~8000 yuan, while the latter is only 1500 yuan.
However, the high luminous efficiency and long life characteristics of LED street lamps can be fully utilized to recover the difference between the initial cost of electricity and maintenance costs.
With the gradual maturity of LED street lighting technology and the continuous decrease of initial cost, its potential advantages in total cost will be revealed in a short period of time.
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