Comprehensive comparative analysis of the performance of high pressure sodium lamps and LED lamps

The life of a lamp refers to the time from the beginning of use to the end of its life. For the life of LED lamps , major manufacturers are now providing the life of the light source for more than a certain number of hours. And calculate the uniformity of illumination . Take the point directly below a light source as the point, draw a vertical line, and intersect the two points AB on both sides of the lane. Illumination uniformity is another very important standard for road lighting. Result: High-pressure sodium lamp 65.77Lux0.38. LED light source has good color rendering and can well restore the actual color of the object, but the white light is cold.

1. About the lighting effects of LED and nano lamps

In 2007, the best LED light source could only reach 80lm/w, and domestic ones were even worse. After the lamps and lanterns, the actual application light efficiency was even lower. At that stage, most LED light sources were used for indicator lighting and landscape lighting, and were not promoted in application environments such as street lighting. However, some unscrupulous manufacturers and a few departments forced it for profit, resulting in actual application failure. Such manufacturers still exist today. But this does not mean that the application of LED has always been this standard. Back then, computers were still 386, but now? We cannot stay at the previous stage when looking at things, but look more at the present and the future. Now OSRAM The normal shipment of kz series light sources is 112-130lm/w.

Take the LED street light with a light source power of 100w as an example: the initial luminous flux is 11200lm. Because LED is unidirectional, the lamp efficiency is high, the lens loss is 10%, and the lamp loss is 10%. The luminous flux of the lamp is 9070lm, and the total power of the lamp is 110w, so the luminous efficiency of this LED lamp is: 82.5lm/w, and the sodium lamp efficiency ranges from 90-140lm/w. However, because it emits light 360 degrees, the light applied to the irradiation direction is very little, only 30%. It is necessary to reflect part of the light in the non-application direction to achieve higher light utilization. Due to the design and cost issues of the lamp, the efficiency of the sodium lamp is only 40-45%.

Take a 250w sodium lamp as an example: the initial luminous flux is 30000lm, and the luminous flux of the lamp is 13500lm. The actual power of the 250w sodium lamp is 300w (this will be explained later), so the luminous efficiency of the 250w sodium lamp is 45lm/w.

Another big problem with sodium lamps is that the lighting continuity of sodium lamps is very poor. When the sodium lamp is in working state, the temperature inside the lamp cavity exceeds 150 degrees. When it is not in working state, the negative pressure sucks in a lot of dust and insects, which greatly affects the lighting effect of the sodium lamp.

From the above results, we can see that the current luminous efficiency of LED lamps is better than that of sodium lamps. With the development and maturity of LED technology, the luminous efficiency of lamps will be greatly improved.

2. About the actual power of LED and sodium lamps

The power composition of LED light source lamps: light source power + power loss = total lamp power. Now the efficiency of LED drivers can reach 91% or even better, and there is no need for reactive power compensation.

The power of the LED lamp with 100w light source before: 100+100*(1-0.91)=109w. The power composition of the sodium lamp is relatively complex, because the efficiency of the sodium lamp is low, only 0.38-0.45, and there is reactive power equal to the swimming power. The apparent power of the 250w sodium lamp is as high as 627va without reactive compensation. In order to solve this problem, the reactive compensation part must be increased. Now the reactive compensation of a single lamp is generally 85%. Sodium lamp Inductor Rectifier loss is 20%, electronic rectifier is 10%, but the cost is high and the life is short.

The previous 250w sodium lamp power is: 250+250*20%=300w. There are also reactive power losses, line losses, transformer losses, etc. in the entire lamp circuit, which will not be added here. Only the lower theoretical value is used for comparison.

3. About the lifespan of LED and sodium lamps

First of all, we must distinguish the concepts of lamp life and average life, and we must not confuse these two concepts.

The life of a lamp refers to the time from the beginning of use to the death of the lamp;

The average life of a lamp is the time from when a batch of lamps begins to be used until half of them die;

As for the life of LED lamps, all major manufacturers are now saying that the life of the light source is greater than a certain number of hours. This statement is unscientific. The theoretical life of LED light sources is very long (provided that it meets the specified temperature range and the L70 light decay standard), but the overall life of a lamp is not simply the life of the light source. The lamp also includes the influence of the driver and lens. Therefore, the final life of the lamp should be limited to the shortest life of all lamp components.

At present, the lifespan of good domestic driver power supplies and lenses made of silicon materials can reach 50,000 hours (provided that the heat dissipation of the lamp meets the requirements).

All manufacturers are talking about the average lifespan of sodium lamps. Some even say that "the average lifespan of sodium lamps used in street lamps is 3 to 5 years, and the energy-saving inductive ballast will not be less than 20 years, and the same is true for lamps." I doubt this statement.

The following are two actual data: "Discussion on the Cost of Single Street Lamp Maintenance" by Baotou Municipal Engineering Management Office

a.1) According to the actual situation in our city, the life of the bulb is calculated as an average of 6,000 hours, the annual lighting time is 3,960 hours, and the theoretical bulb replacement cycle is T=6,000/3,960=1.5 years. The bulb replacement rate is 0.67. According to the actual operation experience of street lamps for many years, the bulb replacement rate should be 0.95.

2) The theoretical life of the ballast is 16,000 hours, the replacement period is T=16,000/3,960=4 years, and the replacement rate is 0.25. Based on many years of operating experience, the ballast replacement rate should be 0.23.

3) The service life of the trigger is set at 1.5 years based on the life of the light bulb, and the replacement rate is about 0.95.

4) The electrical control equipment is calculated based on 3,000 interruptions and a replacement cycle of 4 years, with a replacement rate of approximately 0.23.

b. In the book Street Lights published by Electric Power Press in 2008, there are about 4.13 million sodium lamps in use in more than 600 cities across the country. As of the end of 2007, the national average life of sodium lamps was 4,000 hours.

In the first point, the replacement rate of sodium lamps in actual applications is 0.95, and in the second point, the average life of sodium lamps is only 4000h. From this, we can see that the life of sodium lamps is far less than 3-5 years, which shows that the difference between the results of theoretical analysis and reality is too great.

As for the life of LED street lights, what is it? In the current industry where the quality of LED lamps varies, I think we should first find products that meet some basic requirements of LED lamps for practical application, rather than denying LEDs based on some very bad companies and very bad products.

4. About environmental protection and lighting effects

Sodium lamps contain metallic mercury and sodium, have a short lifespan (compared to LEDs), and subsequent waste disposal causes great environmental pollution. LEDs do not contain the above-mentioned harmful substances or those prohibited by the EU ROHS environmental directive.

a. Glare. It will occur whether it is a sodium lamp or an LED lamp as long as it is a problem with the lamp design. This requires improvements in the lamp lighting design and has little to do with the light source itself.

b. Color rendering. Sodium lamps have poor color rendering and poor reproduction of the original color of objects, which is not conducive to judging the depth of the surrounding environment. LED light sources have good color rendering and can well reproduce the actual color of objects, but the white light is cold.

c. Regarding light transmittance. In foggy weather, vehicles are required to turn on fog lights and drive slowly. Fog lights are not used for lighting, but only for indication.

For road lighting, using a light source with good penetration will only allow you to look up and see a yellow light spot, which has no practical effect on the lighting of the road ahead.

d. Regarding illumination. Illuminance is one of the important criteria for judging lighting effects. Due to the light distribution problem of sodium lamps, the illumination uniformity is not high. In order to achieve better illumination uniformity and effect, many users often over-illuminate in actual applications.

As shown below, a test result in Qingdao :

LED street light Zhongwei Optoelectronics 150W

Induction lamp is Holland Yuding 150W

Xenon lamp manufacturer unknown 150W

High pressure sodium lamp Philips 400W

Date: April 24, 2009

Location: Jinggangshan Road, Huangdao District, Qingdao City, Shandong Province

Organizing unit: Qingdao City Street Light Management Office and individual district street light management offices

Specific location: On the unopened section of Jinggangshan Road, a total of 19 poles are installed, including 5 poles each for high-pressure sodium lamps, electrodeless lamps, and xenon lamps, and 4 poles for LEDs.

The pole is 12-13 meters high and the lamp heads are of different heights), with a spacing of 30 meters, and two lamp heads on the left and right of one pole.

Road conditions: 4 lanes in both directions, 3-meter sidewalk width, 8-meter road width on one side, 4-meter green belt in the middle. Asphalt pavement.

Measurement : In order to avoid interference from other lamps, the working point selected for the illumination test is in the middle two-pole illumination area of ​​each lamp.

Take the point directly below a light source as a point, draw a vertical line, and intersect the two points AB on both sides of the lane. From the two points AB, take 15 meters each, and make two points CD. ABCD is a rectangle with a length of 15 meters and a width of 8 meters. Make a 3*6 grid, a total of 18 working points. Measure the illumination of these 18 working points and take the average value. And calculate the illumination uniformity.

Result: High pressure sodium lamp 65.77Lux0.38

LED21.55Lux0.32

Xenon lamp 22.77Lux.0.17

Electrodeless fluorescent lamp 16.22Lux0.24

in conclusion

1. There is excessive illumination in sodium and other illumination, but the illumination uniformity fails to reach the standard of 0.4 for road lighting. It does not mean that it is not bright enough, but there are light and dark areas (relatively).

2. The illumination of LED street lamps meets the requirements, but the uniformity of illumination does not meet the standards. There is a problem with the light distribution of this product. However, even if the light distribution requirements are met, the actual brightness of the 400w sodium lamp cannot be achieved , because the sodium lamp is excessive lighting.

3. Xenon lamps and electrodeless fluorescent lamps will definitely be eliminated in the future for road lighting with high illumination requirements, but they may still be eliminated for courtyard and community roads.

4. Illuminance uniformity. Illuminance uniformity is another very important standard for road lighting. The current national road lighting standard is 0.3 for branch roads, 0.35 for secondary roads, and 0.4 for main roads.

After the LED light source is lighted, the light pattern is a rectangular spot , which is very suitable for road lighting applications. When the illumination requirements are met, the illumination uniformity can reach 0.8, which is much higher than that of sodium lamps.

The light distribution of sodium lamps is formed by reflection. On the one hand, most of the light is lost, and on the other hand, it is difficult to achieve very good uniformity, that is, to meet the road lighting standards (LEDs were not available when this standard was formulated, and these data were determined based on the best data that lighting could achieve at the time)

5. Regarding heat dissipation, the heat dissipation of LED determines the life and light decay of the lamp. Because the country strongly supports the LED lighting industry, this industry is full of development

Now many companies that were originally in the electronic cooling industry have entered the LED lighting industry, such as Foxconn, Ops (former Jiuzhou Fengshen team), AVC, Coolermaster, etc. Their rich experience in electronic cooling has brought new cooling concepts to LED lamps, which have basically met the requirements of LED temperature control. Take Ops products as an example: at an ambient temperature of 35 degrees, the node temperature can be controlled below 65 degrees.