LED street light contrast with traditional sodium light

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 technology, the rapid development of semiconductor materials application technology, low-power LED light source has been widely used in landscape lighting, high-power LED street lights are also attracting more and more attention.

LED light principle:

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

The principle of light emission of high pressure sodium lamp:

The high-pressure sodium lamp uses an electric arc to generate an arc between the electrodes at both ends of the arc tube. Due to the high temperature of the arc, the sodium amalgam in the tube is evaporated by heat into mercury vapor and sodium vapor, and the electrons emitted by the cathode move toward the anode during impact. The atom of matter, which is energized to produce ionization or excitation, and then returns to the ground state from the excited state; or from the ionized state to the excited state, and then back to the ground state infinite loop, at which time the excess energy is released in the form of optical radiation. It produces light.

The high-power LED street lamp is a new type of illumination method for illuminating the LED group by DC low voltage, which has the characteristics of high brightness, good color rendering, etc. In addition, since the input of the LED street lamp is low voltage DC, it can The combination of solar energy makes solar LED street lights a potential for future road lighting.

1. About energy efficiency analysis and comparison

The lighting installation power of both should be compared in accordance with the same illumination (brightness) level and close lighting quality standards. Because the high-power sodium lamp high-power lamp (250~400W) has high luminous efficiency, it can reach 130~1401m/W, while the low-power lamp (100~150W) has about 40~1001m/W, and the current high-power LED The street lamps use 1W LED tubes, and their light effects are similar. Therefore, it is necessary to analyze the high-power street lamps and low-power street lamps separately.

(1) High-power (≥250W) street light: High-pressure sodium has high light efficiency. Considering three factors such as 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 light effect of LED street lamps is currently about 621m/W in the US, and the best domestic enterprises have reached 56~581m/W. Therefore, the ancient town Runjing street lamp feels that for high-power street lamps, LEDs are currently less energy efficient than sodium lamps.

(2) Low-power (≤150W) street light: The effective light efficiency of the sodium lamp (included in the comprehensive efficiency of 0.55) is about 45~551m/W, while the LED is still calculated according to 56~581m/W, the LED can achieve energy saving compared with the sodium lamp. %~20%, up to 30%. From the above analysis, it can be seen that the LED street lamp can save 10%~30% energy compared to the sodium lamp when the power is small (≤150W) for the branch, and the high power is still not comparable to the energy efficiency of the sodium lamp. Therefore, those who generally claim that LED street lamps are more energy efficient than high-pressure sodium lamps, and even save 50%, 60%, etc., are obviously exaggerated and speculative. We should adhere to the scientific analysis and the principle of seeking truth from facts, otherwise it will easily mislead users and the masses.

2. Analysis of the effect of light source color on road lighting

The color temperature (Tcp) of the high pressure sodium lamp is about 2100K, which is a warm color temperature. The color rendering index (Ra) is only 23~25, and the color rendering is low. The color temperature of the LED street lamp is more than 5300K, which is a cool color temperature. The product has a Ra of 70~80 and good color rendering. As a fast track, main road, and yellow light of the motor vehicle, it is better to see the road surface at a distance of about 90~160m in front, which is better than white light, especially for foggy and dusty air conditions. More advantage. For roads such as sidewalks, commercial pedestrian streets, residential quarters, etc., the color rendering of LEDs is better than that of sodium lamps, which distinguishes people's conditions more clearly and has advantages.

3. Economic analysis and comparison

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