Plant lighting is very hot, but do you really understand?

LED semiconductor lighting network news a few minutes before landing in Guangzhou, passing over Foshan, looking down when it is dark, you will see a "matrix" of light spots. Initially still very confused: What is it? Later I learned that it was the flower growers who provided supplementary lighting to the flower gardens...

Figure: Plant lighting is not easy? Just hanging a light bulb is fine! Scientists and designers cry in the toilet...

In fact, it is not that simple. In this issue, I have specially invited Dr. Xu Dong from Foshan Haoliang Solid Light Source Research Institute to analyze the planting techniques and plant lights for us. What is the relationship between the two?

The design of plant lights is based on the planting process. If the daily radiation of lettuce is too large, it will lead to physiological calcium deficiency, and light inhibition may occur. Reasonable daylighting setting is very important.

The planting process includes: the amount of daily radiation of plant photosynthesis and the total amount of radiation in the planting cycle, plant varieties and provenances, and whether LDP or SDP, planting methods and substrates, planting environment and control.

The spectral shape and daily radiation of the plant lamp closely related to planting are first determined by the planting process of the planting variety. In the design specification of the Institute of Bright Light Source, we use the planting process expert system, the plant planting in the system. The daily radiation amount determines PPFD and photoperiod, PPFD determines PPF, PPF determines plant lamp design and process, PPFD determines the installation height and quantity of lamps, PPDF also determines the ventilation volume and carbon dioxide supplement, these parameters can be calculated by radiation The total amount can be derived from the cost of planting.

Picture: Plant Light Planting Lettuce

It can be seen here that the spectral morphology and the amount of radiation (light quality) first need to determine what environment to plant in what environment to correctly design the spectrum of the LED plant lamp. The planting process is closely related to agricultural planting and industrial control. Internal factors, therefore, the spectral design basis of plant lights can only be derived from the planting process requirements.

Hybrid greenhouse fill light

For greenhouse planting and hybrid plant factories that use a combination of sunlight and fill light, it is accurate to perform spectral analysis of the natural light field to determine the amount of fill light. For sites where conditions are not analyzed, the illuminance value can be tested. The average value, by dividing the average value of the illuminance by 55, can be used to obtain the PPFD value of the planting surface under sunlight, and use this value to determine the amount of light supplemented by the plant lamp. This simple method is very useful for project planning and cost accounting. The greenhouse fill light can reduce or eliminate the green light band, and whether the green light radiation needs to be supplemented by the amount of green light radiation that tests the direct sunlight and scattered light is determined.

Figure: Calculation formula

Figure: Greenhouse planting and hybrid plant plant using a combination of sunlight and fill light

Spectra in a fully artificial environment

Planting in a fully artificial environment, although the red and blue light has a significant effect on the cultivation of leafy vegetables, the taste of hydroponic vegetables is still the key to improving the quality of vegetables. We recommend using white light plus red light spectrum, completely Spectral design in artificial environment requires comprehensive consideration of carbon dioxide concentration, ventilation, ambient temperature, substrate or nutrient solution control, shelf structure design and other factors. Many stacked three-dimensional planting in order to increase the number of planting layers and minimize nutrient solution tanks Height, this method will reduce the balance of nutrient solution and affect the absorption efficiency of the spectrum. The important goal of spectral design under complete artificial environment is the quality control of planting, but the planting process of plant growth is not competitive in the market.

Figure: Plant factory completely using artificial light

About the full spectrum

Some LED plant lights are nominally full spectrum, and may be intended to express their rich spectral content. There is a key concept here, that is, how is the definition of "full" of the full spectrum defined by whom, in the end of the wavelength range? Can width be called "all"?

Although the spectrum of sunlight is the most comprehensive, when studying photosynthesis in sunlight, the PAR value is only described in the range of 400nm-700nm. Many nominal full-spectrum LED plant lights have UV and IR bands. However, PPFD is used to express the parameters. Since PPFD does not describe the amount of UV and IR radiation, the parameter description of this full-spectrum plant lamp shows a low-level error.

We believe that the wavelength range of the plant lamp is only the domain of the spectral absorption efficiency function, not the value range of the absorption efficiency function. The absorption efficiency of the spectrum is an indicator for measuring the photosynthesis effect, and the broad band range or multi-band spectrum is called The full spectrum does not represent the effectiveness and compatibility of plant lights. The use of full spectrum representation of plant lights is not rigorous and often misleads the application of growers;

The definition of the wavelength range of the spectrum is still related to the planting process. It is the definition domain of the planting process that determines the spectral design, not the planting based on the spectrum. The plant lamp and the plant factory are cross-border products. Some phenomena are busy by industrial people. Research and planting, agricultural people are busy studying the spectrum, knowledge extension is only for communication and understanding, professional cooperation and professional division of spectrum design will help the industry to improve rapidly.

Figure: Solar spectrum

Figure: Plant pigment absorption spectrum

Complexity of plant lamp spectral studies

For the LED light source, the same PPFD value, the spectral shape can be different; the same PPFD, secondary optical design requires different ppf values; the same ppf value, the efficiency of the luminaire is different, the PPFD value is also different; ppfd is the same, The shape of the spectrum is not correct, and the planting efficiency is different...

Even if the above conditions are the same, the plant sources are different, the growth environment is different from the substrate, and the planting effect is different.

In addition, the same LED plant lamp is also affected by environmental factors such as carbon dioxide concentration, ventilation, temperature control, etc. Under the planting efficiency and quality meet the requirements of planting process, the plant lamp needs the manufacturing process to ensure that the energy consumption index is minimized. This is very important. The complexity of spectroscopy studies shows the diversity of current plant lights. Since there are no evaluation standards at present, the plant lights on the market are all in full bloom.

The best way to improve the industry - through cooperation with professional technology

Plant lamps involve a wide range of technologies and are cross-border products. No matter how strong the funds are, it is difficult to integrate multidisciplinary talents from the perspective of development costs. Enterprises need to start from their own conditions and solve technical and cost problems. More importantly, It is to solve the technical support problem of after-sales products. For cross-border products, mature experience is the road of cooperative development; agricultural people research the planting process, this is the key to the success of plant lamps and plant factories, and industrial people do well in accordance with the requirements of planting process. Equipment, this affects planting costs and economic benefits, professional cooperation can promote the rapid development of new agricultural planting with controllable artificial environment;

Figure: Calculation and analysis of light radiation distribution

Plant lights are different from lighting. The application of lighting products is the end customer, which can be used for marketing with concepts and prospects. Plant lights are only tools for agricultural planting. Whether the effects are not described by propaganda can be described by actual application. Whether the application of plant lamp can achieve the expected effect is not only the problem of the plant lamp itself, but also related to other technical factors. It is necessary to provide reasonable technical solutions. The marketing of plant lamp belongs to the technical means of technical support as the main means of marketing. Cases often reflect successful technical services. In the absence of technical standards, providing technical solutions is critical and companies need to face them seriously.