What are the commonly used light sources for smart lighting street lights

The commonly used light sources for smart lighting street lamps mainly include fluorescent lamps, high-pressure sodium lamps, low-pressure sodium lamps, and metal halide lamps. In recent years, following the successful development of high-power LEDs, new energy-saving light source LEDs have also attracted widespread attention.

　　 Generally, fluorescent lamps supply more green light, about 50%, and the rest are mostly red and blue light. They also account for about 25% of the total spectrum. The far-red spectrum has a very low share. Fluorescent lamps have high luminous power and long lifespan (about 12000h), but their power is small (28W and 36W are commonly used now), and more lamps are required to meet certain illuminance. Because it contains a lot of green light, it simply constitutes a long crop. Now commonly used in plant tissue culture.

　　 Sodium lamp is a gas luminous light source that emits mercury and sodium vapor. It is divided into low pressure sodium lamp and high pressure sodium lamp. The low pressure sodium lamp appeared earlier, the sodium vapor pressure does not exceed a few Pa, and its emission spectrum is concentrated in the yellow light of 589nm, which can generally only be used in cooperation with other light sources. The luminous power is as high as 200lm/W, and the lifetime is long (about 9000h). The standard operating sodium vapor pressure of the high-pressure sodium lamp is about 10kPa, and there are more red-orange light and less blue-green light in the emission spectrum. The luminous power is high, the power is large, and the lifespan is long (about 12000h), and it is used more now. However, because the high-pressure sodium lamp is a heat source, the surface temperature is high and the heat generation is large, and it cannot illuminate the crops at close range.

　　 metal halide lamp is a gas luminous light source in which mercury and rare metal halide mixed vapor generate arc and discharge light. Different spectra can appear by changing the composition of the metal halide. The luminous power is high, the power is large, and the life span is long (5000h~20000h). However, there is mercury in the filling of the lamp, which will pollute the environment when the lamp used is broken or invalidated and thrown away. The spectrum contains a lot of far-red light, which generates a large amount of heat and cannot illuminate crops at close range.

　　 LED (Light Emitting Diode) light source is a new energy-saving light source developed in recent years. Compared with artificial light sources such as incandescent lamps, fluorescent lamps and high-pressure sodium lamps, LEDs have significant benefits:

　　·DC low voltage power supply. The forward voltage of low-power colorful LEDs is generally 1.5V-2.8V, and the forward voltage of high-power LEDs is generally 3V-4V, which is far less than the safe voltage.

　　·Energy saving. Sodium lamps and metal halide lamps are gas-discharge light-emitting lamps, which emit light by discharging metal element vapor by heating. LED is a solid light source that emits light without heating. It is a cold light source, so it reduces the amount of electricity consumed on heating.

　　·Monochrome light source, high luminous power. LED can emit monochromatic light, and its half-wave width is mostly ±20nm, which can accurately supply the required spectrum for plants without wasting electric energy to declare yellow light, green light and other spectra that plants do not need.

　　·Small size and sensitive application. Lightweight and low-profile lamps can be planned, with large use space.

　　·Environmental protection. LED is a solid luminous light source and does not contain harmful substances such as mercury. It will not cause pollution during the operation of the equipment, and its waste can be recovered. The LED light source is an environmentally friendly green light source.

　　·Long life. LED is a solid light source, there are no loose parts inside, no glass, filament and other vulnerable and burnable parts. It has high mechanical strength, vibration resistance and impact resistance, and its lifespan can reach more than 50,000h.

　　 The obvious advantages of the LED light source of smart street lights have attracted the attention of scholars from the Netherlands, Japan, the United States and other countries. Especially in recent years, the successful development of high-power LEDs has laid the foundation for the use of LEDs in greenhouses.