Analyze LED plant light spectrum technology and parameters

The basis of light research is spectrum. The application quality of light requires spectral analysis. The spectrum of LED plant lights is especially important. The manufacturer's ability to design the spectrum of plant lights determines its market position. The spectrum of LED plant lights needs to be specially designed according to the planting process. To imitation.

The plant factory is a cross-border product. The research institute of the plant is divided into planting equipment technology and planting technology. The plant lamp spectrum technology is an important link between planting equipment and planting technology. It is necessary to clarify the planting process. Spectral design, the design and manufacture of plant lights is to ensure the best efficiency of the light quality required by the planting process. These characteristics of plant lights determine the complexity and diversity of plant spectral design.

1, the application of light classification

Visual application: applied to illumination, the physical unit is based on the average human eye's visual effect function to weight the spectral radiation power as the main parameter.

Non-visual applications: applications such as animal, plant, medical, microbiological, identification, data transfer, etc. The physical unit is the radiated power or the quantum number of light.

2, the energy of photons

LED luminescence is a phenomenon of energy conversion. When electrons and holes recombine, excess energy will illuminate and produce photons. The shorter the wavelength, the higher the energy of photons. The photon is the smallest unit in the process of light transmission energy. It is this kind of photon with energy. Photosynthesis is driven by the photon energy packet instead of the general light energy. This is why plant photosynthesis requires photons to be expressed.

The energy ratio of the energy of a single photon at a wavelength of 400 nm to a wavelength of 700 nm is 1.75, that is, the blue light is 1.75 times larger than the red light energy.

Figure: At the same radiant power, the number of photons produced increases with increasing wavelength.

Photosynthesis is produced by photon flux. It is a process in which photons carrying energy decompose CO2 and H2O under the action of enzymes to produce new molecules. However, not all photons absorbed by plants produce the same photosynthesis, which requires energy transfer. From the perspective of photosynthesis, use "light meals" to understand the relationship between photons and plants.

The number of photons of photosynthetically active radiation is measured in two units: photosynthetic photon flux (PPF) with wavelengths ranging from 400 to 700 nm, and secondly the resulting photon flux (YPF), which can be determined by the photosynthetic response of the plant. The wavelength range.

3. Parameters and units of plant lights

Molar amount (mol)

When describing the basic units of matter composition such as molecules, ions, photons, etc., it is usually expressed in terms of molar amount, which is a basic amount of basic particles of 6.022EXP (23) substances, the unit is: mole (mol), The number of photons in plant photosynthesis is also expressed in terms of molar amount. A photon mole (mol) contains 6.022EXP (23) photons. Many parameters are expressed in micromolar due to the large unit of molars in plant photosynthesis.

1 mole (mol) = 1,000,000 micromolar (umol).

1 micromolar (umol) contains 60 billion photons.

PAR

Photosynthetic Active Radiation

The radiation used by plants for specific wavelength ranges (400-700 nm) for photosynthesis is called photosynthetically active radiation, and there are two types of labeling units:

One is expressed by photosynthetic irradiance (w/m2), which is mainly used for the general study of photosynthesis of sunlight.

The second is the use of photosynthetic photon flux density PPFD (umol / m2s), mainly used for artificial light source and sunlight on plant photosynthesis research.

This method of measuring the photon flux radiated to the surface of the plant per second represents the radiation capability of the radiation source, known as the PPF_PAR method.

PAR accounts for about 50% of the total solar radiation. It should be noted that the unit of photosynthetic irradiance does not reflect the wavelength.

PPF

Photosynthetic Photon Flux refers to the micromolar quantity of photons emitted by artificial light sources per second in the wavelength range of 400-700 nm, in units of umol/s.

PPFD

Photosynthetic Photon Flux Density corresponds to PPF in the number of micromoles radiated per second per square meter of light source, in units of umol/m2s, which is the concept of density.

PPFD is a PPF that represents a range of square meters.

PPFD is a physical quantity related to the radiation distance, which is inversely proportional to the square of the illumination distance.

1PPFD means that 1 micromoles per second of photons are radiated on a surface of 1 square meter.

How big is 1umol/m2s (PPFD), which means there are 6 photons in 10 square nanometers.

YPF

Generated photon flux (Yield Photon Flux)

Refers to the number of micromoles of photons emitted per second in the wavelength range emitted by the artificial light source, in umol/s. The wavelength band is generally considered to be 360-760 nm, and for LED light sources, the wavelength range is set to 380-800 nm.

YPFD

Generated photon flux density (YieldPhotonFluxDensity)

Corresponding to YPF is the number of micromoles per square meter of radiation per second, in units of umol/m2s, which is the concept of density.

YPFD is YPF representing a range of one square meter.

YPFD is a physical quantity related to the radiation distance, which is inversely proportional to the square of the distance of illumination.

YPFD can more accurately express the light quantity of LED plant light.

For red light blue spectrum, YPF = PPF, other spectral PPF.

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 amount derived from planting process parameters, and PPF is the main parameter for lamp manufacturing.

4. Quantitative analysis parameters between different light sources and lamps

For different artificial light sources, the following indicators can be used to compare the performance of spectral parameters between them. These parameters can also compare the performance of spectral parameters of different manufacturers under the same spectral form of the same light source. Generally, the larger the values, the better, but the values Big does not mean that planting efficiency is high and requires professional assessment with professional skills.

PPF/w: indicates the PPF generated per watt of power consumed.

PPFD/w: indicates the PPFD generated per watt of power consumed.

YPF/w: indicates the YPF generated per watt of power consumed.

YPFD/w: Indicates the YPFD generated per watt of power consumed.

These values ​​are related to the spectral form (light quality). If you divide these values ​​by the price of the plant lamp, you can compare the price of the plant lamp. The validity of these values ​​needs to be reliable by independent third-party professional analysis.

Typically, agricultural sodium lamps are up to 2.2 umol/w, LED sources, up to 2.1 umol/w.

5, light quality, light quantity, photoperiod

Light quality LQ

Light Quality (LQ) is a spectral form in a certain wavelength range, without units.

Light quantity LI

Light Intensity (LI) is the number of photons that can be radiated by the light quality. It can be expressed by photon flux or by photon density. The unit is PPF (YPF) or PPFD (YPFD).

Photoperiod PP

Photo Period, which is the sum of time, in hours, when the plant lights are turned on during a natural day.

6. The amount of radiation that plants need every day (important concept)

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

Usually, the compensation point and the saturation point appear only for a certain period of time, not constant. It is not scientific to set the PPFD with the compensation point and the saturation point. In our planting process expert system, we give the plant every square meter per day. The amount of radiation that is reasonably needed, this value is related to planting cost and planting quality. Our parameter is based on the planting process parameter DLI for long-term research in agricultural science, which has theoretical basis.

Daylight DLA

Daily light amount (DLA): refers to the number of moles of photons generated per square meter of PPFD per day during the photoperiod of the artificial light source, in mol/m2d.

Since the amount of light of the plant lamp is constant under the photoperiod, DLA = 0.0036 * PPFD * PP. PP-photoperiod unit: hour.

DLA is a planting process parameter, and the PPFD required for plant planting in a plant factory is calculated using DLA.

Disclaimer: The DLA parameters are defined by Xu Dong, a research institute for bright and solid light sources.

Daylight integral amount DLI

Daily light integral (DLI): refers to the amount of photosynthesis per square meter per day of effective sunlight, in mol/m2d.

DLI is an important photosynthetic parameter in traditional planting. It is a technical parameter for long-term agricultural scientific research. It has universal planting guiding significance. Under sunlight, due to the photosynthetic irradiance of sunlight (converted into PPFD) with time and weather. In the ever-changing, this change will occur between the compensation point and the saturation point. Therefore, the DLI needs to be calculated according to the integral method. The preliminary calculation can be calculated by the average PPFD and the effective time (hours).

DLI calculated according to the average method under sunlight, DLI = 0.0036 * PPFD (average) * effective time. Effective time unit: hour.

In outdoor planting, the DLI parameters will be affected by the saturation point. In the greenhouse, the indoor DLI is smaller than the outdoor DLI. The DLI of the greenhouse is usually smaller than the DLA. The establishment of the DLA parameters scientifically provides whether the greenhouse fills light or not. The theoretical basis for the amount of fill light, the establishment of the DLA database of artificial light source, can provide the basic data system for plant plant application, which is of great significance, and hopes that agricultural researchers will participate in this work.

DLA is the main parameter of planting plant and greenhouse light-filling planting process. It is the main basis for plant lamp design. DLA can be obtained through experimental data or weighted by DLI, but it needs experimental data correction. The relationship between DLA and DLI is : DLA, such as lettuce, dli is 17 and dla is 9-11.

The above is the introduction of the spectral parameters of the plant lamp. It is very important to understand the parameters of the plant lamp. It is very important for the application and communication of the plant lamp. The standardized use of these parameters can correctly apply the plant lamp and research the plant lamp spectrum technology.

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