Currently used artificial lighting technologies in greenhouses are fluorescent lamps, high pressure sodium lamps, low pressure sodium lamps and metal halide lamps. In recent years, with the emergence and development of LED lighting technology, LED lights drives, this new energy-saving lighting source drew a lot of attention.
Traditional fluorescent lamps provide more green rays (about 50%), the rest are mainly composed of red rays and blue rays (about 25%). The proportion of infrared rays is negligible. It is known that green rays are the “main engine” for pants growing. Grow lights using fluorescent-powder-involved LED lighting sources have much higher lighting efficiency, longer service life (about 12000 hours), lower power consumption (commonly used are 28W and 36W). All these LED grow lights can completely take place of sunlight to provide sufficient lights for fruits and vegetables.
Sodium lamps are a type of lighting sources that use mercury and sodium vapor to generate high brightness light, which can be divided into low pressure sodium lamps and high pressure sodium. Sodium lights (LP) appeared earlier than sodium lights (HP), equipped with LED street lighting suppliers, with a sodium vapor pressure less than several Pa. Their wavelength is concentrated around 589nm (yellow rays). Thus in most cases, they can only be used under the coordination of other lamps. Sodium lamps (LP) have very high lighting efficiency (200lm/W). The standard gas pressure of sodium lamps (HP) is 10kPa, much higher than sodium lamps (LP). They send out more red-yellow rays but very few green-blue rays, equipped with LED PWM dimming suppliers, high lighting efficiency, high power consumption, long service life (12000 hours). Sodium lamps (HP) is the most commonly used lighting source in plant lighting area, and also the closest competitors of LED lighting sources. Since sodium lamps (HP) used thermal lighting sources, which will generate a large amount of heat during operation, they cannot be used in short-distance plant lighting applications.
The rare metal halide vapor and mercury mixture within metal halide lamps can generate electric in given conditions. They are a type of lamps that emit light through discharge, equipped with electrical switches, spectrum of which can be adjusted by changing the mixture constitution of metal halide, high power consumption, long service life (5000 – 20000 hours). Because of the abundant internal mercury, the recycling of these lamps will bring about a lot of pollution our environment. Similar to sodium lamps, metal halide lamps used thermal lighting sources and cannot be used in short-distance lighting applications.