How does LED Grow Light affect the growth rate of cannabis?

一 LED Grow Light basic parameters

1, LED light-emitting principle

LED light emission is a phenomenon of energy conversion. When electrons and holes recombine, the excess energy will emit light and produce photons. The shorter the wavelength, the higher the energy of the generated photons. Photons are the smallest unit in the process of light transfer energy and are absorbed by plant photosynthesis. It is this kind of energetic photon.

2. The nature of plant photosynthesis

Photosynthesis is a process in which energy-carrying photons decompose CO2 and H20 under the action of enzymes to produce new molecules.

3. The number of photons of photosynthetically active radiation

Two measurement units are used: photosynthetic photon flux (PPF), whose wavelength ranges from 400 to 700 nm, and the second is the generated photon flux (YPF), whose wavelength range can be determined according to the photosynthetic response of the plant.

4. Parameters and units of LED grow lights

1) Molar quantity (mol): The molar quantity is a basic quantity composed of 6.022EXP (23) elementary particles of a substance. The unit is: mole (mol). The number of photons in plant photosynthesis is also expressed in molar quantity. The photon mole (mol) contains 6.022EXP(23) photons. Because the unit of mole is large in plant photosynthesis,-generally expressed in micromole. 1 mole (mol) = 1000000 micromole (umo1). One micromole (umo1) contains 6 quadrillion photons.
 

2) Photosynthetically active radiation (PAR): The radiation in the specific wavelength range (400-700nm) used by plants for photosynthesis is called photosynthetically active radiation, and there are two labeling units:
One is expressed by photosynthetic irradiance (w/m2), which is mainly used for generalized research on photosynthesis of sunlight.
The second is expressed by the photosynthetic photon flux density PPFD (umol/m2s), which is mainly used for the study of plant photosynthesis by artificial light sources and sunlight.
 

3) Photosynthetic photon flux (PPF): refers to the number of micromoles of photons emitted by artificial light sources per second in the wavelength range of 400-700nm, in umol/s.
 

4) Photosynthetic photon flux density (PPFD): Corresponding to PPF is the number of micromoles radiated by the light source per square meter per second, in umol/m2s, which is the concept of density.
PPFD is the PPF expressed in one square meter. PPFD is a physical quantity related to the radiation distance, which is inversely proportional to the square of the radiation distance. 1PPFD means that 1 micromole of photons per second radiates on a surface of 1 square meter. How big is 1umol/m2s (PPFD)? It means there are 6 photons in 10 square nanometers.
 

5) Generated photon flux (YPF): refers to the number of micromoles of photons radiated per second in the wavelength range emitted by the artificial light source, unit umo1/s. The generally considered wavelength range is 360-760nm. For LED light sources, the wavelength range is set to 380-800nm.
 

6) Generated photon flux density (YPFD): Corresponding to YPF is the number of micromoles of radiation per square meter per second, the unit is umol/m2s, which is the concept of density.
YPFD means YPF in the range of one square meter. YPFD is a physical quantity related to radiation distance, which is inversely proportional to the square of the radiation distance. YPFD can more accurately express the light quantity of LED Plant light. For red and blue spectra, YPF=PPF, other spectra PPF<YPF.
The difference between PAR and PPFD, PAR is a physical concept, and the unit of this physical concept of PPFD. The relationship between PPFD and PPF: PPFD is the basic quantity derived from planting process parameters, and PPF is the main parameter for lamp manufacturing.
For the same PPF light source, the relationship between the installation height and PPFD is that the installation height increases, and the PPFD decreases at a rate of 2 power.

5. Quantitative analysis parameters between different light sources and lamps

For different artificial light sources, the following indicators can be used to compare their spectral parameter performance. These parameters can also be compared with the spectral parameter performance of different manufacturers under the same spectral form of the same light source. Generally, the larger the value, the better. However, the value Large does not mean that the planting efficiency is high, and a professional assessment with professional skills is required.
PPF/w: Indicates the PPF produced per watt of power consumption. PPFD/w: Represents the PPFD produced per watt of power consumption. YPF/w: Indicates the YPF produced per watt of power consumption. YPFD/w: Indicates the YPFD produced per watt of power consumption.
If you divide the above number by the price of Plant light, then you can compare the price of Plant light. The validity of these values requires independent professional analysis by a third party to be reliable. Generally, the agricultural sodium lamp is up to 2.2umo1/w, and the LED light source is up to 2.1umol/w.

6. Light quality, light quantity, light cycle

Light quality LQ: is the spectral form within a certain wavelength range, without unit.
Light quantity LI: is the number of photons that can be radiated by light quality, which can be expressed by photon flux or photon density, unit: PPF (YPF) or PPFD (YPFD).
Photoperiod PP: Represents the sum of the time the Plant light is turned on in a natural day, unit: hour.

7. The amount of radiation that plants need every day

Many people are keen to study the compensation point and saturation point of plant radiation to estimate how much PPFD should be used for Grow Light. The range from the compensation point to the saturation point is large (as shown in the figure below), and the amount of light in this range is artificial. The randomness, the compensation point and the saturation point are only qualitative analysis. The quantification process must consider other environmental factors, and cannot be understood mechanically.

Usually, the compensation point and saturation point only appear in a certain period of time and are not constant. It is not scientific to set the PPFD with the compensation point and saturation point. In our planting technology expert system, we give the plant per square meter per day The amount of radiation that is reasonably required is related to the planting cost and planting quality. This parameter of ours is based on the planting technology parameter DLI, which has been studied for a long time in agricultural science, and has a theoretical basis.
 

Total amount of daylight DLA: refers to the number of moles of photons produced by artificial light sources per square meter of PPFD per day under the photoperiod, unit: mol/m2d. The amount of light of Grow Light is constant under the photoperiod, DLA=0. 0036* PPFD*PP. DLA is a planting process parameter, and the PPFD required for plant planting in a plant factory is calculated using DLA.
Daylight integral DLI: refers to the integral amount of photosynthesis per square meter per day under the effective solar radiation, unit: mol, /m2d.
 

DLI is an important photosynthetic quantity parameter in traditional planting. It is a technical parameter of long-term agricultural scientific research and has universal planting guidance. Under sunlight, the photosynthetic irradiance (converted to PPFD) of sunlight changes with time and weather. In constant change, this change will sometimes span between the compensation point and the saturation point. Therefore, DLI needs to be calculated in accordance with the integral method. The preliminary calculation can be calculated using the average PPFD and the effective time (hours).
 

DLI calculated by the average method under sunlight, DLI=0. 0036*PFD (average) * effective time. Effective time unit: hour.
In outdoor planting, the DLI parameter will be affected by the saturation point. In the greenhouse, the indoor DLI is smaller than the outdoor DLI, and the DLI of the greenhouse is usually smaller than the DLA. The establishment of the DLA parameter scientifically provides whether the greenhouse is supplemented with light or not. The theoretical basis of the amount of supplementary light and the systematic establishment of a DLA database of artificial light sources can provide a basic data system for plant factory applications. It is of great significance. It is hoped that agricultural researchers will participate in this work.
 

DLA is the main parameter of the planting process for plant factories and greenhouses. It is the main basis for the design of Grow Light. DLA can be obtained through experimental data or weighted through DLI, but it needs to be corrected by experimental data. The relationship between DLA and DLI is : DLA<DLI
 

The above is the introduction of Plant light spectrum parameters. It is very important to understand these parameters of Grow Light for the application and communication of Plant light. The standardized use of these parameters can correctly apply Plant light and study plant light spectrum.

二 Performance comparison between LED plant lights and HID lights

HID refers to a class of gas discharge lamps including high pressure and low pressure sodium (HPS), mercury vapor (MV) and metal halide (MH). Before the invention of LED lamps, HID lamps have always been the dominant position of Plant lighting.

1. Light effect (lumens per watt)

Compared with other types of traditional artificial lighting, today's double-ended HPS lamps are quite efficient, producing more than 100 lumens per watt. The light output of the LED light laboratory has exceeded 300 lumens per watt. With the advancement of technology, the efficiency of LEDs continues to increase, and the cost per lumen output is also falling.

2. Reflection efficiency

HID lamp is a diffuse light source, it needs a reflector fixture, the reflectivity of the best reflective material used in the fixture is about 95%, it usually may have a lot of reflection, so even the best HID lamp, its overall lamp The efficiency is usually only 85% or lower. Since LEDs are directional, there is no reflection loss.

3. Lamp degradation and spectral instability

After one-year operation, the output power of HID lamps may be reduced by 10-15%. In the case of HPS, when they degrade, the spectrum shifts to the green/yellow range, which is the worst range of the spectrum. Plant utilization. Therefore, most professional growers replace HID lights at least once a year. The rated life of the LED lamp is at least 50,000 hours, the output power drops by less than 10%, and it will usually continue to work beyond its rated value with almost no change in the spectrum.

4. Cooling requirements.

The inner wall temperature of HID lamps is about 400 degrees Celsius, so if cooling is not used, they may become a potential fire hazard. About 75% of all energy consumed by HID lamps is emitted in the form of heat, and most of the heat is in the form of infrared (IR) radiation. Therefore, not only does the HID system require a lot of air conditioning, but the high level of IR can heat the blades without increasing the air temperature. Compared with HID, LEDs usually generate 50% less heat, and most of the heat from the LEDs is generated from the back of the circuit board and transferred to the heat sink instead of being radiated to vegetation.

5. Fixed spectrum output of HID

LED is the only-lighting technology that can be designed to meet the specific spectrum of plants. A single LED chip produces a very narrow spectrum band, so LED growth lights can be precisely mixed to provide an optimized spectrum to maximize the absorption and utilization of plants.

6. LED is safe, simple and easy to use

Compared with the non-ventilated HID system, LED does not need to replace the lamps, and the cooling requirement is reduced by 40-50%. They will never cause a fire hazard in the close range of a growing tent, and they produce almost no layered infrared (IR) radiation.
It is for these reasons that LED grow lights have become the first choice to replace HID as garden lighting.

三 Features and Advantages of LED Grow Light lighting

1. Features of LED Grow Light

1) Different wavelengths of light have different effects on plant photosynthesis. The light required for plant photosynthesis has a wavelength of about 400-700nm. 400-500nm (blue) light and 610-720nm (red) contribute the most to photosynthesis.
2) Blue (470nm) and red (630nm) LEDs can just provide the light needed by plants, so the ideal choice is to use a combination of these two colors. In terms of visual effects, the plant light with a combination of red and blue appears pink.
3) Blue light helps plant photosynthesis, which can promote green leaf growth, protein synthesis, and fruit formation; red light can promote plant rhizome growth, help flowering and fruiting and prolong flowering, and increase yield!
4) The ratio of red and blue LEDs of LED Plant light is generally between 4: 1--9: 1, and usually 6-9: 1.
5) When plant light is used to supplement light for plants, the height from the leaves is generally about 0.5-1 meters, and continuous exposure for 12-16 hours a day can completely replace sunlight.
6) The effect is very significant, and the growth rate is almost 3 times faster than that of natural plants.
7) Solve the problem of lack of sunlight in the greenhouse in winter, promote the chlorophyll, anthocyanin and carotene needed in plant photosynthesis, so that fruits and vegetables are harvested 20% earlier, increasing the yield by 3 to 50%, and improving the sweetness of fruits and vegetables. And reduce pests and diseases.
8) LED light source is also called semiconductor light source. This kind of light source has a relatively narrow wavelength and can emit light of a specific wavelength, so it can control the color of the light. Using it to irradiate plants alone can improve plant varieties.
9) LED grow light has low power, but extremely high efficiency, because other lights emit full spectrum, that is to say, there are 7 colors, but plants need only red light and blue light, so most of the light energy of traditional lights is wasted , So the efficiency is extremely low. And LED grow light can emit specific red and blue light that plants need, so it is extremely efficient. This is why LED grow light with a power of several watts is better than a lamp with a power of tens or even hundreds of watts. Another reason is the lack of blue light in the spectrum of traditional sodium lamps, and the lack of red light in the spectrum of mercury lamps and energy-saving lamps, so traditional lamps have a much worse light-filling effect than LED lamps, and they save more than 90% of energy compared to traditional lamps. The operating cost is greatly reduced.

2. Advantages of LED plant lights

1) No standard power socket connectors for drivers or cooling fans are required.
2) An environment with red and blue wavelengths is required for plant growth.
3) Compared with other ordinary lighting equipment, LED Plant light has a milder line and will not scorch seedling plants.
4) Compared with other Plant lighting, it can save 10%~20% of electricity bill.
5) Blue light can promote plant growth, and red light can make plants flower and bear fruit.

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