At present, the greenhouse artificial light sources mainly are fluorescent lamps, high pressure sodium, low pressure sodium, metal halide lamps act. In recent years, with the successful development of high-power LED, the new energy-saving LED light source also attracted widespread attention.

The ordinary fluorescent lamp provides more green, about 50%, most of the rest are red and blue, which take about 25% of the total spectrum, infrared spectral ratio is very low. Fluorescent lamp with luminous efficiency 80lm/W, long life (about 12000h), and CRI>85, but less power (currently used both 28W and 36W). Because it contains a lot of green light, which likely to cause crop growth, commonly used in plant tissue culture.

Sodium lamp is mercury and sodium vapor light, it is divided into two kinds as low pressure sodium lamp and high pressure sodium. Low pressure sodium appeared earlier, the sodium vapor pressure is not more than a few Pa, and the emission spectrum is mainly in the 589nm yellow, usually only used complexes with other light sources. The luminous efficiency is up to 200lm / W, long life (about 9000h). High pressure sodium standard vapor pressure is about 10kPa, the emission spectrum most are red-orange light and a little blue-green light. It with high luminous efficiency, high power, long life (about 12000 h), it used a lot in the greenhouse. However, due to the high pressure sodium lamp is heating source, with high surface temperature, the lamp can not shoot the crop in closed distance.

The metal halide lamp is a gas light source, that mixed vapor of mercury and the rare metal halide, then generated arc, thereby discharge light. It can emit different spectral by changing the metal halide composition. Its luminous efficiency is high as 65-140lm/W, also high power, and long life (5000h to 20000h). But metal halide lamp contains mercury; it will pollute the environment when the lamp is breakdown or abandon. Its spectrum contains a lot infrared light, produces more heating, and also can’t shoot the crop in closed distance.

LED (Light Emitting Diode) is a solid-state semiconductor devices that can convert electrical energy into visible light; it can convert electrical to light directly. The heart of LED is a semiconductor wafer. And LED light is the lamps that used LED as light source. Compare to the up lamps, it’s have the following features:
1) High energy efficient: it can achieve 100-150lm/W.
2) Long life as 50000h.
3) LED light in theoretically, its spectral characteristics include the entire visible spectral range. Color Rendition Index is 70-90.
4) Environmental protection: it doesn’t contain mercury or xenon and other harmful elements, also does not produce radiation, it is recyclable.

Obviously, Countries all over the world take more and more attention to the problem of energy-saving and environmental protection, some countries are already promoting the use of LED lamps. As long as the of LED lamps cost reduce, and LED technology continues to improve, it will replace the fluorescent lamp, Sodium lamp, the metal halide light inevitablely.