Analysis: LED street lighting technology is not yet mature

Recently heard the views of many experts and scholars believe that LED as a street lamp to replace the high-pressure sodium lamp is technically immature. The main reasons are the following:

The luminous efficiency of 1.LED is not comparable to that of high pressure sodium lamp

The irradiation of 2.LED is too concentrated, the irradiation uniformity is poor

The long light 3.LED lamp is serious, life is not long

4.LED light is not stable (short-term depreciation), over time, seasonal changes

5.LED Street itself is too heavy, is not conducive to installation, wind.

6.LED street lamp cost is too high, can not be universal.

Of course, all of these are based on the experience of many domestic test lines. There is a certain basis. However, the performance of the domestic test line can not represent the current situation of LED is worth exploring.

1 luminous efficiency problem

At present, the luminous efficiency of LED is not as good as the number of high-pressure sodium lamp. The current LED in the 6575 LM / W, and high pressure sodium lamp can reach 125 LM / W. However, the spectrum of HPS are relatively concentrated in yellow, its temperature is relatively low and only 20002500oK, LED can achieve higher color temperature, more than 35004500. In addition, the high-pressure sodium lamp is sent to the surrounding light, a large part of the light can not reach the road. In addition, the high pressure sodium lamp color rendering index is poor, only 20 to 40, the feeling of darkness; and LED color rendering index is high, can reach 75 - 80. So the road is bright and comfortable. So from the actual luminous effect, LED can be much higher than the high pressure sodium lamp. 100W LED can be replaced by 250W high pressure sodium lamp, or 300W mercury lamp. 100W LED, the output luminous flux is only about 6250 lumens (by two optical design, will be lost), when the road reached lumen is still 6000 lumens, and average road surface illuminance can reach 16Lux (12m bar). 250W high pressure sodium lamp output luminous flux of 20000 lumens. But the number of lumens to reach the road is only 7000 lumens. The illumination of the road surface is about 30 - 40Lux, because of the difference of color rendering coefficient, the correction coefficient of LED is about 2.35 times, and the correction coefficient of high pressure sodium lamp is about 0.94 times. So after the correction of the 100W LED of the ground illumination is 37.6Lux, and the correction of high pressure sodium lamp illumination is 28.2-37.6. Two equivalent. So, 100W LED can replace the 250W high-pressure sodium lamp, LED can save energy 2.5 times.

2 irradiation uniformity problem

Indeed, if not for the two optical design, LED exposure is more concentrated, so must be two times the optical design, the light intensity of a bat shaped. So the problem is easy to solve.

Light 3.LED

Now some businesses, in order to reduce costs, the use of hundreds of phi 5 small power LED. However, the small power LED light is very serious, in accordance with its decline to 80% of the life of only 1000 hours. Therefore, as the need for long-term use of street lamps is absolutely not allowed to use this small power LED. As a large power LED, the light will be better. However, many domestic manufacturers can only do 10000 hours down by 10%. Far can not meet the use requirements.

In fact, the LED life problem is mainly due to long-term work in high temperature and the formation of the problem. Life at different junction temperatures as shown below:

When the junction temperature is increased from 115 to about 135 degrees, the service life is reduced from 50000 hours to 20000 hours. At present, the luminous efficiency of LED has not been raised to a high degree, but also to improve its heat dissipation to extend the life of LED.