The plant factory combines modern industry, biotechnology, nutrient solution cultivation and information technology to implement high-precision control of environmental factors in the facility. It has full closure, low requirements for the surrounding environment, shortens plant harvest period, saves water and fertilizer, and has no The advantages of pesticide production and non-discharge of waste are 40~108 times of the production efficiency of open land. An intelligent artificial light source and its light environment control play a decisive role in its production efficiency.
As an important physical environmental factor, light plays a key role in regulating plant growth and material metabolism. “One of the main features of plant factories is the full artificial light source and the intelligent regulation of the light environment” has become a common consensus in the industry.
Plant Demand For Light
Plant life activities are inseparable from light. Light is the only source of energy for plant photosynthesis. Light intensity, light quality (spectrum) and periodic changes of light have a profound impact on crop growth and development, and photosynthesis of plants by light intensity The effect is the biggest.
Light Intensity
The intensity of light can change the shape of the crop, such as flowering, internode length, stem thickness, and leaf size and thickness. Plants' requirements for light intensity can be divided into hi-light, hi-light, and low-light plants. Most of the vegetables belong to hi-light plants, and their light compensation points and light saturation points are relatively high. In the artificial light plant factory, the relevant requirements of crop light intensity are an important basis for selecting artificial light sources. Understanding the illumination requirements of different plants is to design artificial light sources. Improving the production performance of the system is extremely necessary.
Light Quality
Light quality (spectral) distribution also has an important impact on plant photosynthesis and morphogenesis. Light is part of the radiation, and radiation is an electromagnetic wave. Electromagnetic waves have wave characteristics and quantum (particle) characteristics. The quantum of light is called photon, and it is also called photon in the field of horticulture. Radiation with a wavelength range of 300-800 nm is called physiologically active radiation of a plant, and radiation with a wavelength range of 400-700 nm is called photosynthetically active radiation (PAR) of a plant.
Photoperiod
The relationship between photosynthesis and photomorphogenesis of plants and the length of day (or light period) is called the photoperiod of plants. Periluminality is closely related to the number of hours of illumination, and the number of hours of illumination refers to the time when the crop is illuminated by light. Different crops require a certain amount of light hours to complete the photoperiod. According to the different photoperiod, it can be divided into long-day crops, such as cabbage, which require more than 12~14h of light hours at a certain stage of birth; short-day crops, such as onions and soybeans, need 12~14h or less. Light hours; medium-day crops, such as cucumbers, tomatoes, peppers, etc., can bloom and bear under long or short sunshine.
Among the three elements of the environment, the light intensity is an important basis for selecting artificial light sources. At present, there are various expression methods for light intensity, including the following three types.
(1) Illumination refers to the luminous flux surface density (luminous flux per unit area) accepted on the illuminated plane, in units of lux (lx).
(2) Photosynthetically active irradiance PAR, unit: W/m² .
(3) Photosynthetically active photon quantum density PPFD or PPF is the photon number of photosynthetically active radiation arriving or passing per unit time per unit area, in units of μmol/(m²·s). Mainly refers to the light intensity of 400~700nm directly related to photosynthesis. It is also the most commonly used indicator of light intensity in the field of plant production.
Light Source Analysis Of Typical Fill Light System
The artificial fill light is achieved by installing a fill light system to increase the light intensity in the target area or prolong the illumination time to achieve the plant's light demand. In general, fill light systems include fill light devices, circuits, and their control systems. The fill light source mainly includes several common types such as incandescent lamp, fluorescent lamp, metal halide lamp, high-pressure sodium lamp and LED plant lamp. Due to the low efficiency of incandescent lamps and low efficiency of photosynthetic energy, they have been eliminated by the market.
Fluorescent Lamp
Fluorescent lamps are a type of low-pressure gas discharge lamp. The glass tube is filled with mercury vapor or an inert gas, and the inner wall of the tube is coated with a phosphor, and the color of the light varies depending on the fluorescent material applied in the tube. The fluorescent lamp has good spectral performance, high luminous efficiency, low power, long life (12000h) compared with incandescent lamps, and relatively low cost. Because the fluorescent lamp itself generates less heat, it can be placed close to the plant for illumination. It is suitable for three-dimensional cultivation, but the spectral layout of the fluorescent lamp is unreasonable. The internationally common method is to add a reflector to maximize the effective light source component of the crop in the cultivation area. Japan's adv-agri company has also developed a new fill light source HEFL. HEFL is actually a category of fluorescent lamps. It is a general term for cold cathode fluorescent lamps (CCFL) and external electrode fluorescent lamps (EEFL). The HEFL lamp is extremely thin, with a diameter of only about 4mm. The length can be adjusted from 450mm to 1200mm according to the cultivation needs. It is an improved version of the conventional fluorescent lamp.
Metal Halide
The metal halide lamp is a high-intensity discharge lamp which is formed by adding various metal halides (tin bromide, sodium iodide, etc.) to the discharge tube to generate different wavelengths on the basis of the high-pressure mercury lamp. The halogen lamp has high luminous efficiency, high power, good light color, high life, and a large spectrum. However, since the luminous efficiency is lower than that of the high-pressure sodium lamp, the life is shorter than that of the high-pressure sodium lamp, and it is currently used only in a few plant factories.
HPS
High-pressure sodium lamps are of the type of high-pressure gas discharge lamps. The high-pressure sodium lamp is a high-efficiency lamp in which a high-pressure sodium vapor is charged in a discharge tube and a small amount of cesium (Xe) and a halide of a mercury lamp metal is added. Because high-pressure sodium lamps have high electro-optical conversion efficiency and low manufacturing cost, high-pressure sodium lamps are the most widely used in agricultural facilities for light-filling applications. However, due to the shortcomings of low photosynthetic efficiency, low-efficiency short-boards are caused. On the other hand, the spectral components emitted by high-pressure sodium lamps are mainly concentrated in the yellow-orange light band, lacking the red and blue spectrum necessary for plant growth.
LED
As a new generation of the light source, light-emitting diode (LED) has higher electro-optical conversion efficiency, adjustable spectrum and high photosynthetic efficiency. LED can emit monochromatic light required for plant growth. Compared with ordinary fluorescent lamps and other complementary light sources, LEDs have the advantages of energy saving, environmental protection, long life, monochromatic light, and cold light source. As the electro-optical efficiency of LEDs further increases, the cost of scale effects decreases, and LEDs will become the mainstream equipment for agricultural facilities.
By comparison, the characteristics of different fill light sources can be clearly understood, as shown in Table 1.
Want to learn more about LED plant lights? You can click on the article:
《Can Be Eaten The Vegetable Which Grows With The LED Grow Lights》
《The Prospects of LED Grow Lights For Development 》
《Why We Need LED Grow Lights?》
The Design Idea of Typical Crop Fill Light System
The design of the plant factory fill light system is usually designed with the core content of the light intensity, light quality and photoperiod parameters of different crop growth stages and special means of end regulation, and relies on the intelligent control system to implement the implementation, achieving the ultimate goal of energy saving and high yield.
At present, the design of the fill light design for leafy vegetables has gradually matured. For example, leafy vegetables can be divided into four stages: seedling stage, middle growth stage, late growth stage, and terminal treatment; fruit vegetables can be divided into the seedling stage, vegetative growth stage, flowering stage and harvesting stage. From the light intensity of the fill light, the light intensity at the seedling stage should be slightly lower, at 60~200 μmol/(m?·s), and then gradually increase. Leaf vegetables can reach up to 100~200 μmol/(m?·s), fruit vegetables can reach 300~500 μmol/(m?·s), to ensure the photosynthesis requirements of photosynthesis in different growth stages, and to achieve high yield. For the light quality, the ratio of red to blue is crucial. In order to increase the quality of the seedlings and prevent the length of the seedlings, the ratio of red and blue is generally set at a lower level [(1~2): 1], and then gradually reduced to meet the needs of plant light form formation, and the leaf red and blue ratio can be compared. Settings (3~6): 1. For the photoperiod, similar to the light intensity, it should show an increasing trend with the extension of the growth period, so that the leafy vegetables have more photosynthesis time for photosynthesis. The light-filling design of fruit and vegetables will be more complicated. In addition to the above basic rules, we should focus on the photoperiod setting during flowering, and we must promote the flowering results of vegetables so as not to be counterproductive.
It is worth mentioning that the light formula should include the end-disposal light environment setting content, for example, the continuous supplementation of light can greatly improve the yield and quality of the hydroponic vegetable seedlings, or the UV treatment can significantly improve the sprouts and leafy vegetables (especially The nutritional quality of purple leaves and red leaf lettuce）.
It is not difficult to find that the LED light source equipment is most in line with the current development trend in order to cope with the weak light and ultraviolet light caused by bad weather such as cloudy weather and haze and to ensure high-yield and stable production of facility crops.
In the future, the development direction of plant factories should be re-typed with high-precision, low-cost sensors and remotely controllable, tunable spectral fill light system and expert control system. At the same time, the future plant factory will continue to develop with low cost, intelligence, and adaptability. The use and popularization of LED light source provide high-precision environmental control for plant factories. LED light environment regulation is a complex process involving light quality, light intensity, photoperiod, and other comprehensive control. It is believed that with the further research of LED fill light illumination and With the promotion, plant factories will play an important role in our lives.
《The Analysis of Vertical Farm Development Prospect》
《How To Build A Successful Plant Factory?》
《The Problems In Greenhouse And How To Solve Them?》
As an important physical environmental factor, light plays a key role in regulating plant growth and material metabolism. “One of the main features of plant factories is the full artificial light source and the intelligent regulation of the light environment” has become a common consensus in the industry.
Plant Demand For Light
Plant life activities are inseparable from light. Light is the only source of energy for plant photosynthesis. Light intensity, light quality (spectrum) and periodic changes of light have a profound impact on crop growth and development, and photosynthesis of plants by light intensity The effect is the biggest.
Light Intensity
The intensity of light can change the shape of the crop, such as flowering, internode length, stem thickness, and leaf size and thickness. Plants' requirements for light intensity can be divided into hi-light, hi-light, and low-light plants. Most of the vegetables belong to hi-light plants, and their light compensation points and light saturation points are relatively high. In the artificial light plant factory, the relevant requirements of crop light intensity are an important basis for selecting artificial light sources. Understanding the illumination requirements of different plants is to design artificial light sources. Improving the production performance of the system is extremely necessary.
Light Quality
Light quality (spectral) distribution also has an important impact on plant photosynthesis and morphogenesis. Light is part of the radiation, and radiation is an electromagnetic wave. Electromagnetic waves have wave characteristics and quantum (particle) characteristics. The quantum of light is called photon, and it is also called photon in the field of horticulture. Radiation with a wavelength range of 300-800 nm is called physiologically active radiation of a plant, and radiation with a wavelength range of 400-700 nm is called photosynthetically active radiation (PAR) of a plant.
Photoperiod
The relationship between photosynthesis and photomorphogenesis of plants and the length of day (or light period) is called the photoperiod of plants. Periluminality is closely related to the number of hours of illumination, and the number of hours of illumination refers to the time when the crop is illuminated by light. Different crops require a certain amount of light hours to complete the photoperiod. According to the different photoperiod, it can be divided into long-day crops, such as cabbage, which require more than 12~14h of light hours at a certain stage of birth; short-day crops, such as onions and soybeans, need 12~14h or less. Light hours; medium-day crops, such as cucumbers, tomatoes, peppers, etc., can bloom and bear under long or short sunshine.
Among the three elements of the environment, the light intensity is an important basis for selecting artificial light sources. At present, there are various expression methods for light intensity, including the following three types.
(1) Illumination refers to the luminous flux surface density (luminous flux per unit area) accepted on the illuminated plane, in units of lux (lx).
(2) Photosynthetically active irradiance PAR, unit: W/m² .
(3) Photosynthetically active photon quantum density PPFD or PPF is the photon number of photosynthetically active radiation arriving or passing per unit time per unit area, in units of μmol/(m²·s). Mainly refers to the light intensity of 400~700nm directly related to photosynthesis. It is also the most commonly used indicator of light intensity in the field of plant production.
Light Source Analysis Of Typical Fill Light System
The artificial fill light is achieved by installing a fill light system to increase the light intensity in the target area or prolong the illumination time to achieve the plant's light demand. In general, fill light systems include fill light devices, circuits, and their control systems. The fill light source mainly includes several common types such as incandescent lamp, fluorescent lamp, metal halide lamp, high-pressure sodium lamp and LED plant lamp. Due to the low efficiency of incandescent lamps and low efficiency of photosynthetic energy, they have been eliminated by the market.
Fluorescent Lamp
Fluorescent lamps are a type of low-pressure gas discharge lamp. The glass tube is filled with mercury vapor or an inert gas, and the inner wall of the tube is coated with a phosphor, and the color of the light varies depending on the fluorescent material applied in the tube. The fluorescent lamp has good spectral performance, high luminous efficiency, low power, long life (12000h) compared with incandescent lamps, and relatively low cost. Because the fluorescent lamp itself generates less heat, it can be placed close to the plant for illumination. It is suitable for three-dimensional cultivation, but the spectral layout of the fluorescent lamp is unreasonable. The internationally common method is to add a reflector to maximize the effective light source component of the crop in the cultivation area. Japan's adv-agri company has also developed a new fill light source HEFL. HEFL is actually a category of fluorescent lamps. It is a general term for cold cathode fluorescent lamps (CCFL) and external electrode fluorescent lamps (EEFL). The HEFL lamp is extremely thin, with a diameter of only about 4mm. The length can be adjusted from 450mm to 1200mm according to the cultivation needs. It is an improved version of the conventional fluorescent lamp.
Metal Halide
The metal halide lamp is a high-intensity discharge lamp which is formed by adding various metal halides (tin bromide, sodium iodide, etc.) to the discharge tube to generate different wavelengths on the basis of the high-pressure mercury lamp. The halogen lamp has high luminous efficiency, high power, good light color, high life, and a large spectrum. However, since the luminous efficiency is lower than that of the high-pressure sodium lamp, the life is shorter than that of the high-pressure sodium lamp, and it is currently used only in a few plant factories.
HPS
High-pressure sodium lamps are of the type of high-pressure gas discharge lamps. The high-pressure sodium lamp is a high-efficiency lamp in which a high-pressure sodium vapor is charged in a discharge tube and a small amount of cesium (Xe) and a halide of a mercury lamp metal is added. Because high-pressure sodium lamps have high electro-optical conversion efficiency and low manufacturing cost, high-pressure sodium lamps are the most widely used in agricultural facilities for light-filling applications. However, due to the shortcomings of low photosynthetic efficiency, low-efficiency short-boards are caused. On the other hand, the spectral components emitted by high-pressure sodium lamps are mainly concentrated in the yellow-orange light band, lacking the red and blue spectrum necessary for plant growth.
LED
As a new generation of the light source, light-emitting diode (LED) has higher electro-optical conversion efficiency, adjustable spectrum and high photosynthetic efficiency. LED can emit monochromatic light required for plant growth. Compared with ordinary fluorescent lamps and other complementary light sources, LEDs have the advantages of energy saving, environmental protection, long life, monochromatic light, and cold light source. As the electro-optical efficiency of LEDs further increases, the cost of scale effects decreases, and LEDs will become the mainstream equipment for agricultural facilities.
By comparison, the characteristics of different fill light sources can be clearly understood, as shown in Table 1.
Want to learn more about LED plant lights? You can click on the article:
《Can Be Eaten The Vegetable Which Grows With The LED Grow Lights》
《The Prospects of LED Grow Lights For Development 》
《Why We Need LED Grow Lights?》
The Design Idea of Typical Crop Fill Light System
The design of the plant factory fill light system is usually designed with the core content of the light intensity, light quality and photoperiod parameters of different crop growth stages and special means of end regulation, and relies on the intelligent control system to implement the implementation, achieving the ultimate goal of energy saving and high yield.
At present, the design of the fill light design for leafy vegetables has gradually matured. For example, leafy vegetables can be divided into four stages: seedling stage, middle growth stage, late growth stage, and terminal treatment; fruit vegetables can be divided into the seedling stage, vegetative growth stage, flowering stage and harvesting stage. From the light intensity of the fill light, the light intensity at the seedling stage should be slightly lower, at 60~200 μmol/(m?·s), and then gradually increase. Leaf vegetables can reach up to 100~200 μmol/(m?·s), fruit vegetables can reach 300~500 μmol/(m?·s), to ensure the photosynthesis requirements of photosynthesis in different growth stages, and to achieve high yield. For the light quality, the ratio of red to blue is crucial. In order to increase the quality of the seedlings and prevent the length of the seedlings, the ratio of red and blue is generally set at a lower level [(1~2): 1], and then gradually reduced to meet the needs of plant light form formation, and the leaf red and blue ratio can be compared. Settings (3~6): 1. For the photoperiod, similar to the light intensity, it should show an increasing trend with the extension of the growth period, so that the leafy vegetables have more photosynthesis time for photosynthesis. The light-filling design of fruit and vegetables will be more complicated. In addition to the above basic rules, we should focus on the photoperiod setting during flowering, and we must promote the flowering results of vegetables so as not to be counterproductive.
It is worth mentioning that the light formula should include the end-disposal light environment setting content, for example, the continuous supplementation of light can greatly improve the yield and quality of the hydroponic vegetable seedlings, or the UV treatment can significantly improve the sprouts and leafy vegetables (especially The nutritional quality of purple leaves and red leaf lettuce）.
It is not difficult to find that the LED light source equipment is most in line with the current development trend in order to cope with the weak light and ultraviolet light caused by bad weather such as cloudy weather and haze and to ensure high-yield and stable production of facility crops.
In the future, the development direction of plant factories should be re-typed with high-precision, low-cost sensors and remotely controllable, tunable spectral fill light system and expert control system. At the same time, the future plant factory will continue to develop with low cost, intelligence, and adaptability. The use and popularization of LED light source provide high-precision environmental control for plant factories. LED light environment regulation is a complex process involving light quality, light intensity, photoperiod, and other comprehensive control. It is believed that with the further research of LED fill light illumination and With the promotion, plant factories will play an important role in our lives.
《The Analysis of Vertical Farm Development Prospect》
《How To Build A Successful Plant Factory?》
《The Problems In Greenhouse And How To Solve Them?》
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