Commonly used LED light source in the greenhouse and its characteristics

At present, commonly used artificial light sources for greenhouse lighting include fluorescent lamps, high-pressure sodium lamps, low-pressure sodium lamps, and metal halide lamps. In recent years, with the successful development of high-power LEDs, new energy-saving light sources have attracted widespread attention.

Ordinary fluorescent lamps provide more green light, about 50%, and most of the rest are red and blue light, which respectively account for about 25% of the total spectrum, and the far-red spectral ratio is very low. Fluorescent lamps have higher luminous efficiency and long life (about 12,000 hours), but they have lower power (at present, 28W and 36W are commonly used), and more lamps are required to satisfy a certain degree of illumination. Because it contains a lot of green light, it can easily lead to crops. Currently used in plant tissue culture.

The sodium lamp is a gas light source that emits mercury and sodium vapor and is classified into low pressure sodium lamp and high pressure sodium lamp. The low-pressure sodium lamp appeared earlier, and the sodium vapor pressure did not exceed a few Pa. Its luminescence spectrum was concentrated at the yellow light of 589 nm, and it was usually used only with other light sources. Luminous efficiency up to 200lm/W, long life (about 9000h). The standard sodium vapor pressure of the high pressure sodium lamp is about 10 kPa, and there are more red orange light and less blue-green light in the luminescence spectrum. High luminous efficiency, high power, long life (about 12000h), currently used in the light in the greenhouse. However, since the high-pressure sodium lamp is a heat source, the surface temperature is high and the amount of heat is large, and the crop cannot be irradiated at a short distance.

A metal halide lamp is a gas light source that emits light by arcing with a mixture of mercury and a rare metal halide to generate light. By changing the composition of the metal halide, it exhibits a different spectrum with higher luminous efficiency, high power, and long life (5000h to 20000h). However, there is mercury in the filler in the lamp. When the used lamp is damaged or thrown away, it will cause environmental pollution. The spectrum contains more far-red light, and the heat is too high to illuminate the crop at close range.