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Comparison of LED Street Lamps and Traditional Sodium Lamps
Jun 09, 2018

Comparison of LED Street Lamps and Traditional Sodium Lamps

At present, China is creating a resource-saving and environment-friendly society, and the concept of “green lighting” is gradually gaining popularity. With the continuous advancement of science and technology, the rapid development of semiconductor material application technology, low-power LED light sources have been widely used in landscape lighting, and high-power LED street lights have also attracted more and more attention.

LED light emitting principle:

LED (Light Emitting Diode), a light emitting diode, is made of a group III-IV compound and is a solid-state semiconductor device that can directly convert electricity into light. The heart of the LED is a semiconductor wafer. The semiconductor wafer consists of three parts, a part of which is a P-type semiconductor in which holes are dominant and the other end is an N-type semiconductor. When current is applied to the wafer through the wire, electrons and holes are pushed into the vector well. In the quantum well, electrons recombine with holes, and then they emit energy in the form of photons. This is the principle of LED light emission. The wavelength of light, which is the color of light, is determined by the material that forms the P-N junction.

High-pressure sodium lighting principle:

The high-pressure sodium lamp utilizes the electric arc between the electrodes at both ends of the arc tube after being energized, and the sodium amalgam in the tube is heated to vaporize into mercury vapor and sodium vapor due to the high temperature of the arc, and the electrons emitted from the cathode move toward the anode during the impact discharge. The atom of matter, which causes it to gain energy to produce ionization or excitation, and then returns from the excited state to the ground state; or from the ionized state to the excited state, and then back to the base state in an infinite cycle. At this time, the excess energy is released in the form of light radiation. It produces light.

The high-power LED street lamp is a new lighting method that realizes the lighting demand by lighting the LED group by DC low-voltage, and has the characteristics of high brightness and good color rendering; in addition, since the input of the LED street lamp is low-voltage direct current, it can The combination of solar energy makes solar LED street lamps become a possible way of future road lighting.

1. About energy efficiency analysis and comparison

The lighting installation power should be compared between the two in accordance with the same illumination (brightness) level and close to the lighting quality standard. Due to the high luminous efficiency of high pressure sodium lamps (250~400W), the luminous efficiency is up to 130~1401m/W, while that of low-power lamps (100~150W) is approximately 80~1001m/W, and the high-power LEDs are now used. The street lamp uses 1WLED tube more, its light efficiency is similar, so should analyze high power street lamp and low power street lamp respectively.

(1) High-power (≥250W) street lights: High-pressure sodium lighting effects are high. Consider ballast loss, lamp efficiency, and track utilization. If the overall efficiency is 0.55, the effective light efficiency of the sodium lamp is about 70~751m/W; and the effective luminous efficiency of LED street light is currently about 621m/W in the United States, and the best domestic company has reached 56~581m/W. Therefore, the ancient town of Runjing street lamp that for high-power street lights, the current LED light energy efficiency is lower than the sodium lamp.

(2) Low-power (≤ 150W) streetlights: The effective luminous efficacy of sodium lamps (total efficiency 0.55 is included) is about 45~551m/W, while the LED is still 56~581m/W, LED can achieve energy saving than sodium lamps. %~20% up to 30%. From the above analysis, it can be seen that for low power (≤ 150W) for branches, LED street lamps can save energy by up to 10%~30% compared to sodium lamps, and the high power is still inferior to that of sodium lamps. Therefore, those who claim that LED street lights are more energy-efficient than high-pressure sodium lamps can save 50%, 60%, etc., are obviously exaggerated and speculative. We should adhere to scientific analysis and the principle of seeking truth from facts, otherwise it is easy to mislead users and the general public.

2, light source color light on the road lighting effect analysis

The correlated color temperature (Tcp) of the high pressure sodium lamp is about 2100K, which is a warm color temperature. Its color rendering index (Ra) is only 23~25, and its color rendering is low; while the color temperature of the LED street lamp is now more than 5300K, which is a cool color temperature, better The product has Ra up to 70~80 and good color rendering. As a fast-moving road and main road for motor vehicles, the sodium lamp with yellowish light is slightly better than white light for seeing the distance between 90 and 160 meters in front of the road surface, especially for fog and dusty air conditions. More advantages. For roads such as sidewalks, commercial pedestrian streets, residential quarters, and other roads, the color rendering of LED street lamps is better than that of sodium lamps, and the situation of distinguishing people is clearer and has advantages.

3, economic analysis and comparison

High-pressure sodium lamps, each about 1200 ~ 1500 yuan; current LED lights, according to the power of different sizes, the price difference is larger, about 4000 ~ 8000 yuan. As far as the status quo is concerned, LED street lights are obviously too expensive and the price is as high as 3 to 5 times. As before, LEDs with less than 150W can save energy by 10%~30%. Each year, the electricity consumption per lamp is about 50~150KWh, so it is impossible to recover the cost of buying lamps. It can only be expected that in the coming years, LED development trends will see its price gradually decline, energy efficiency further improved, and its economic performance will be compared.

4, service life analysis

Comparison of service life should be based on the entire lamp life. High-pressure sodium lamps include light sources, electrical accessories (mainly ballasts, triggers) and luminaires. Sodium lamps are used for average lamp life of 3 to 5 years, energy-saving inductive ballasts are not less than 20 years, and so are lamps. However, the service life of LED street lamps has no use experience. The existing enterprises are known as 50,000, 60,000 hours, and there is no reliable basis. The requirements formulated by the US Energy Star are divided into not less than 35,000h and 25000h. The main reason is that LED chips have a long life. However, they have a lot to do with the temperature, heat dissipation and other factors after the package. There are also electronic devices that drive the circuit devices. Component life problems, such as capacitors often only 8000h to 10000h. Therefore, as a whole, the service life of LED street lamps cannot be compared with that of sodium lamps.

5, maintain performance comparison

Users represented by urban street lamp management departments are more concerned about the maintenance performance of street lamps. According to the analysis, the maintenance performance of the sodium lamp is good. The lamps need only to be scrubbed, they do not need to be replaced, the ballasts are rarely replaced, and the light source is changed once every 3 to 5 years. It is also very convenient. LED street lamps, LED tubes, modules (including lenses, etc.), power supply devices, etc., have a high possibility of damage to components and components, and are difficult to maintain and replace. They are likely to be replaced as a whole and the cost is high. solve. LED street lamps have no standards to follow, and they are unfavorable for bidding and ordering and for use and maintenance. In summary, we believe that LED street lighting is a new thing that has emerged in recent years. With the development of the LED industry, there will be greater development and broad prospects. However, there are still many problems in the current status of the application. Although a small number of LED street lamps research, development and production companies have made great efforts to solve some technical problems and promote the advancement of the product, they do not care about the industry's elite; However, as a whole, the level, quality, unevenness, and diversity of LED street lighting products are very different. There are no standards to regulate, some are quick success, the energy efficiency of the products is not high, the heat dissipation problem is not handled well, the light failure is great, and the service life is not long. , There is no reasonable lighting distribution, can not meet the requirements for promotion. We hope that scientific research, teaching, design agencies, use units, and manufacturing companies will work together to solve various technical problems, improve product levels, formulate and improve a series of standards, and make preparations for promotion and application. In the promotion and application, we should adhere to gradual and orderly progress, starting from the pilot, summing up experience, and continuing to improve; we should start with small-power LED street lamps for branch roads and residential roads, and then develop trunk roads and high-power street lights to gradually advance. No matter what light source or luminaire is used, it should meet the requirements of the “City Lighting Design Standards” (CJJ45-2006), including brightness, illuminance, evenness and other quality indicators. Adhere to the principle of seeking truth from facts, avoid excessive exaggeration, avoid comparisons and avoid raising yourself, and avoid pressing down others, insisting on lighting quality, lighting (brightness), insisting on the combination of technology and economy, applying energy-saving and environmental protection, and preventing excessive hype. Service, responsible for the user, do not mislead the user, but also a real user appearance. Do not swear to “replace” what light source. It should be after several years or several years of efforts to continuously improve itself so as to become a new type of high quality and efficient light source and luminaire in road lighting for users to choose. Let the user speak and let the use effect evaluate. Luminous efficiency: The unit is lumens per watt Lm/w. That is, the ability of an electric light source to convert electric energy into light energy is expressed by the luminous flux emitted divided by the power consumption.

6, luminous efficiency

The luminous efficiency of LED light sources is currently around 75 Lm/w in the US and Japan, and about 65 Lm/w in domestic production. The luminous efficiency of the HPS light source is about 100 Lm/w, and the luminous flux emitted per W is 25 to 35 Lm/w higher than that of the LED. 400w high pressure sodium lamp luminous efficiency up to 120Lm/w.

7, fogging

In road lighting, there is a big misunderstanding about the penetration of LED lights for heavy fog. Most people think that the penetration of LED street lamps is lower than that of traditional lighting sodium lamps. This is a misunderstanding. Most people mostly see some information on the Internet or see the feelings of some of the senses on the road. They did not do scientific assessment and analysis, and they believe that the light penetration of LED street lamps is poor. This article will make a scientific analysis of this situation.

Huzhou Jiwei Electronics Technology Co., Ltd

Address: No. 35, Wuxing Technical Zone, Huzhou City, Zhejiang, China 313000

Tel:  +86-572-2299226

Fax:  +86-572-2299223 



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