For a long time, planting plants under artificial light has aroused wide interest in the industry, not only because of limited urban space, but also because of the conditions that can control plant growth. The interest in gardening has increased significantly as the growth rate of flowers and fruits is found to vary according to the spectrum provided to plants. Think about how many flowers you need to cultivate on Valentine's Day, or imagine the pressure on suppliers to supply fresh fruits and vegetables to the supermarket at the appointed time. Together with the horticulture industry and universities, Osram optoelectronic semiconductors and other major lighting manufacturers investigated how light affects different plants.
We now know that green plants are basically using blue light (about 430 to 490nm) and red light (about 640 to 780nm), mainly for photosynthesis, so they are used to generate energy, but there are other absorption bands, such as the infrared range of about 730nm (see Figure 1), which controls plant growth and so on.
The correct mix, coupled with a temporary increase in certain wavelengths suitable for individual plant needs, can trigger the desired effect. LED is particularly suitable for this application due to the determination of the color spectrum and control flexibility. For optimum plant growth, the above wavelength range of light must be provided and no overall white appearance is required. If these parameters are properly executed, plants can be cultivated in closed spaces under artificial light, away from wind and rain.
At the same time, omni-directional lighting means that plants consume less energy in vertical growth, or they need to find sunlight. Instead, they grow more outward and produce higher yields. Creating a good environment for plants poses a challenge to lamps and LEDs. Because the sprinkler system used in commercial greenhouses produces high humidity, LEDs should withstand environmental impacts or be protected. Chemicals or ash layers contaminated with fertilizers or pesticides may also penetrate LED lamps.
Key parameters of product development: stability and output
From this and other areas of application, can be based on lumen packaging, light quality and packaging size, and many other details of targeted product development. The LED package is essentially different on two parameters, namely the output level and the "stability". The "stability" of the LED assembly includes not only enhanced reliability, but also the operating temperature and environmental parameters required for a particular application. Low-stability LEDs can have a very long service life, but only in moderate conditions. Higher stability means more complex, more expensive materials, more complex processes, and therefore higher costs. Therefore, in most cases, the parts should be selected according to the stability of the LED specific application.
The output level or the amount of light emitted per package is another key factor. Led in a linear or panel luminaire with a large number of individual small lumen packages. In the application of directional light or even specific distributed light, the large lumen encapsulation is used, which is more suitable for the "point Light source" of two times optics. In the middle, there is a series of classic lamps and lamps, through a small number of medium-range lumen encapsulation or a large lumen package to achieve the previous incandescent lamp standard luminous flux.
Select the correct LEDs for the application
Experience has shown that many LEDs optimized for specific applications can also be used very successfully in other areas, with little modification or even modification. In order to define suitable led packages in all areas of general lighting, it is necessary to differentiate between output levels and package stability. However, technological innovations and improvements that have been established in the LED market cannot be overlooked. New application areas such as horticultural lighting are presenting new challenges to product developers that they have to overcome. The above results show that although there are appropriate LEDs for almost all established applications, this does not preclude the possibility of a more suitable led in the future, or the presence of areas that have so far not been considered.