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How important the supplementary lighting system in the greenhouse farming

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Update time : 2018-05-16 09:10:12
Application of artificial light system in modern glass greenhouse.
Artificial light system is the core element of indoor planting.
In modern glass greenhouse, the water, CO2, temperature, humidity, can be precisely controlled plant nutrition supply, artificial light system becomes the main factor of greenhouse crop actual output.
Applied to artificial light source, there are many kinds of optical system, such as fluorescent lamp, plasma lamp, metal halide lamp (including metal halide lamp and ceramic metal halide lamp), high pressure sodium (HPS), light emitting diode (LED), etc.
So far, the most successful application of large-scale production in greenhouse is high pressure sodium lamp, metal halide lamp and LED.
Green plants absorb light energy and use light to assimilate carbon dioxide (CO2) and water (H2O) to produce organic matter and release oxygen.
Plants have several plant pigments that absorb light energy and provide photosynthesis, but the most common and effective use of photosynthesis is chlorophyll.
Plant leaves contain two chlorophyll - chlorophyll a and chlorophyll b.
In red and blue region has absorption peak, yellow/green spectroscopy can be other absorbed by plant pigments such as carotene and other light without being absorbed by leaf reflection (this gives the green plants), you can see the spectral composition of more than 50% of the reflected off or underused.
1. Introduction of light source type of artificial light system.
High pressure sodium lamp
Spectra of the most popular 600W and 1000W agricultural sodium lamps in commercial glasshouses.
High - pressure sodium lamps are very effective in the greenhouse of growing crops, because high - pressure sodium lamps have very high light output.
Philips 1000 w high pressure sodium lamp, for instance, can reach more than 15 Wan Liuming light output and more than 2100 mu PPFD mol/s. (m2), maintain and output rate is also very good, in the case of using 10000 h, still can ensure the output characteristic of more than 95%.
However, the high pressure sodium lamp also has some disadvantages, such as the increase in the power of power, the blue spectral composition is less.
Ceramic metal halide lamp (CMH)
The ceramic gold halide lamp has more blue light than sodium lamp.
In the past few years, the ceramic metal halide lamp has been successfully applied to the plant growth stage, which can achieve a high PAR value output [over 1.7 mmol /(m2·s)].
The disadvantages of ceramic gold halide lamp in greenhouse are relatively obvious, such as low power density and high heat generation.
Light-emitting diode (LED)
Compared with the high-pressure sodium lamp and the gold halide lamp, the LED can simply choose the light of different wavelengths (color temperature).
This means that leds can meet the specific spectral needs of plants in different growth stages by designing different spectra.
"White light" leds themselves are impossible to exist.
White leds are "encapsulated" in two forms, the first and the rarest of them, which is the combination of red, green and blue LED chips to produce white.
But due to the green LED is expensive and inefficient, so is the most common type of white LED by the blue LED chip and the lens coated with phosphor, is to use the blue leds emit blue light to excite the phosphor.
The optimal design for plant growth is called a spectrum.
The mixed spectrum is shown in figure 5.
The spectrum of LED lamps can be mixed according to the actual needs of the crops, and leds with mixed spectra are highly efficient.
However, the spectral LED has its disadvantages, such as low power density compared with high pressure sodium lamp and ceramic metal halide lamp, and no radiation heat.
2. The successful application of artificial light system in commercial glass greenhouse.
Top high pressure sodium lamp system.
The top high pressure sodium lamp system is a stable artificial light system.
Up to now, more than 90% of the artificial light systems that have been grown in scale use the top high pressure sodium lamp as the light source to fill the light, and the yield is considerable.
At present, the problem of high pressure sodium lamp artificial light system solution is that more than 2/3 of the light needs to be reflected to the surface of the crop using reflectors.
The reflectance efficiency of the reflector is very serious, which makes the actual output efficiency of the high-pressure sodium lamp system only 50%~70%.
And because the light source and reflector have no fixed position is very good, a lot of light in the process of reflection by the high pressure sodium lamp light core, this makes greatly reduces the actual service life of the high pressure sodium lamp.
The top high pressure sodium lamp and the top metal halide lamp system.
The top high pressure sodium lamp and the top gold halide lamp system are the strongest light intensity and the closest approach to the solar spectrum.
The biggest disadvantage of this system is that the demand for power is quite large, and it generates a lot of heat at the same time.
The real full spectrum light source (target spectrum) is obtained by mixing the metal halide lamp and sodium lamp core.
High pressure sodium lamp at the top and plant.
The high - pressure sodium lamp at the top and plant is the most productive artificial light system at present.
In Russia and northern Europe, there are very good examples.
HellenOY (Finland) and Reflux (Russia) have very good design.
The artificial light system can produce the highest yield, but requires sufficient power supply.
Top high pressure sodium lamp and plant LED.
The top high pressure sodium lamp and the plant LED are the most efficient artificial light system solutions.
The increase of the total output of LED plants with a density of 50W/m2 in the artificial light system of the top high pressure sodium lamp can increase the total output by more than 20%.
Through the test data of Khosla, it can be seen that when the power density of the inter-plant LED is increased to 50W/m2, the output will be improved.
Top LED and plant LED.
Top LED and plant LED may become the most efficient artificial light system solution.
Theoretically, through the top and plant LED artificial light system, it can provide the customized spectral and light intensity for the plant.
But it is also the most expensive artificial light system, and there are already several large projects running that will see results in the coming year.
Conclusion 3.
Artificial light systems have become increasingly important in commercial greenhouses.
A common greenhouse, such as more than 10 hm2 greenhouse, through the use of artificial light system, 3 ~ 5 years can recycling costs, instead of using artificial light system requires 8 ~ 10 years (the Russian ministry of agriculture data, 2017).
How to get the most efficient and low-cost artificial light system is still an important issue for people.
Up to now, there are two kinds of artificial light systems to choose from, the top high power high-pressure sodium lamp system and the top high power high voltage sodium lamp and low power plant LED artificial light system.
However, for researchers and research institutions, the artificial light system LED by the top is the best research direction.