With the development of LED technology, the United States, Japan, South Korea, etc. have taken LED agricultural lighting applications as an important development direction, and many domestic and foreign manufacturers have also entered the field of agricultural lighting. The application of LED light source in agricultural lighting mainly includes plant production, aquaculture, microalgae cultivation, edible fungus production, etc. It is widely used in European and American countries and has achieved good economic benefits. In April 2010, Japan's Mitsubishi Chemical Corporation used a large-scale waste container to transform it into a plant factory, supplemented by modern information management technology and LED as a light source for crop photosynthesis. In order to meet the needs of the new plant factory, Japan Showa Denko has developed LED products for the “plant factory†that can emit red light of a specific wavelength that promotes the growth of crops.
It was adopted by more than 10 plant factories in Japan, and its sales in 2010 reached 1 billion yen [1]. LED agricultural lighting in Europe, especially in the Nordic region, has also developed rapidly. Due to geographical location, the Nordic region has been in a semi-polar and semi-polar state for a long time. Temperature and light are not conducive to the growth of crops. After adopting greenhouses and LED lighting technology, agricultural products are used. The quality has been greatly improved and the supply of agricultural products in the country has been maximized. The US Department of Agriculture has allocated significant funds to fund Purdue University's LED lighting technology research to improve agricultural development in a hostile natural environment.
At present, LEDs have been adopted in domestic agricultural lighting, such as the establishment of solar photovoltaic LED plant factories in the Yangling Agricultural Demonstration Zone in Shaanxi. In addition to some applications, the development of related technologies for LED applications in the agricultural sector has also received increasing attention. In December 2010, the “Plant Factory Innovation Achievements Conference†was held at the Chinese Academy of Agricultural Sciences. Beijing Zhongda Yida Facilities Horticulture Technology Co., Ltd. launched a family version of the plant factory and family gardening products, which were respectively associated with Philips Lighting of the Netherlands and Mitsubishi Chemical of Japan. Dozens of internationally renowned companies such as Panasonic (China) Electrician, Taiwan Everlight, Yangzi Electric, Ou Lin Group and so on signed a strategic cooperation agreement on technological innovations in LED plant lighting sources, industrial control, air conditioning environmental control, nutrient solution preparation, etc. Market development and other agreements have been reached.
1 Analysis of the advantages of LED light source in the field of agricultural lighting
In recent years, with the large-scale promotion of greenhouses in agricultural production, the research progress of artificial climate chambers and the improvement of agricultural science and technology, it has become more and more important to carry out research on rational greenhouse light supply and reduce light cost. The light-feeding measures have become a research hotspot, and the successful development of new luminescent materials provides an opportunity to solve this problem. New energy-efficient LED plant lights are the best choice. LED lamps have many advantages such as high luminous efficiency, low heat generation, small size and long life. The advantages in agricultural lighting are obvious. The main performance is that the bio-energy efficiency is high, which can greatly increase the plant cultivation density.
LED energy-saving effects from agricultural lighting applications are significant.
LED agricultural lighting source is a special lighting tool, plant growth requires sunlight, and LED agricultural lighting source is the principle of using sunlight, using light instead of sunlight to become a source of plant growth and development environment. At present, the traditional artificial illumination source is lacking compared with the LED illumination source: firstly, the spectrum of the artificial illumination source is basically a linear line, which is not ideally matched with the plant photosynthetic absorption spectrum. Only the light of individual bands can be absorbed by plants, and the light of other bands is wasted, and energy is not saved. In addition, due to the large power consumption of incandescent bulbs, fluorescent tubes, sodium lamps, etc., and at the same time generating a lot of heat radiation, plants can not be irradiated at close range, and the efficiency of excitation of plant growth light is not high, which greatly increases the cost of artificial illumination. Some high value-added flower planting and artificial climate chamber tests have not been widely used in agricultural production.
The light environment is one of the important physical environmental factors indispensable for plant growth and development. Controlling plant morphogenesis through light quality regulation is an important technology in the field of facility cultivation. The main effects of light spectrum on plant photosynthesis are red light and blue light. The red light is mainly concentrated in 630-660 nm. Its function is to help plants to bloom. The blue light is mainly concentrated in 450-470 nm. Its role is to help plants grow. Stem leaves [2]. The application test results show that the wavelength of LED agricultural illumination source is very suitable for plant growth, flowering and results [3]. In general, indoor plants and flowers will grow worse with time. The main reason is the lack of light irradiation. It can not only promote the growth of LEDs through the spectrum of plants, but also extend them.
Long flowering period, improve the quality of flowers. Applying this high-efficiency light source system to agricultural production and breeding of greenhouses, greenhouses, etc. can produce the following effects: 1 As a supplemental illumination, the illumination can be enhanced at any time of the day, which can prolong the effective illumination time. 2 Whether at dusk or at night, it can effectively extend and scientifically control the light required by plants. 3 In the greenhouse or plant laboratory can completely replace natural light to promote plant growth. For most growers, LED plant lights are the best source of light for sunlight. Because its spectrum is completely based on the spectral design required for plant growth, it has high brightness and long life. 4 Thoroughly solve the situation of watching the day of eating at the nursery stage, and arrange the time according to the delivery time of the seedlings.
Having full-spectrum illumination in the greenhouse is critical to plant growth. The plant illumination source used in the early days was not a full-spectrum light source and could not fully provide the illumination needed for plant growth. The newly launched plant-grown high-light sodium lamp now has full-spectrum properties that provide all the light needed for plant growth, greatly reducing the time required for plant growth. Therefore, its emergence is a technological revolution in the field of plant lighting, and has become the best choice for light sources in this industry, widely used in the fields of aqueous solution cultivation, sowing, breeding, flower cultivation and so on.
2 LED light source market demand analysis in the field of agricultural lighting
The lighting fixtures used in traditional agricultural production are mainly high-pressure sodium lamps, fluorescent lamps and incandescent lamps. Among them, high-pressure sodium lamps and incandescent lamps are mainly used for greenhouse fill light in winter and spring when the light time is short or rainy days. Because of the high luminous efficiency and long service life of high-pressure sodium lamps, the use area is wide. Take a set of Philips high-pressure sodium lamps (including lamps, rectifiers and reflectors) used in greenhouses, with a power of 400 W, a price of 300-400 yuan, a luminous efficiency of 120 lm / W, and a luminous flux of 47 000 lm. The average service life is 24 000 h. At present, the world glass greenhouse area is about 49,000 hm2, while China is about 0.35 million hm2. According to a sodium lamp of 15 m2, China needs 2.3 million 4,386 high-pressure sodium lamps to meet the production needs. Thus, the light source device needs to be used once. Sexual investment was 700-900 million yuan, and the demand of the whole world reached 32 million, and the one-time demand investment reached nearly 10 billion yuan. If all of these greenhouses in the world are operated with high-pressure sodium lamps for 1 h, they will consume 13 million kWh. Calculating the world's 2.38 million hm2 of agricultural greenhouse LED lighting needs, the number will be more than dozens of times.
At present, fluorescent lamps are commonly used as artificial illumination sources in closed plant growth systems (such as plant tissue culture, plant factories, edible fungi factories, etc.), and the use in tissue culture production is most common. For example, a common 10 m2 tissue culture chamber using a Philips T5 trichromatic fluorescent tube has a length of 86 cm, a diameter of 16 mm, a power of 28 W, a price of 18 to 20 yuan, and a luminous efficiency of 100 lm / W, luminous flux 2 900 lm, service life 24 000 h. In the tissue culture room, the tissue culture frame is often set according to the length of the lamp tube. Each layer has an area of ​​90 cm×50 cm, a total of 3 layers, and a 10 m2 tissue culture room can be placed with 10 3-layer cultivation frames, 5 lamps per layer. A total of 150 lights are required. According to the statistics of the Ministry of Agriculture, as of the end of 2007, the total area of ​​plant tissue culture was over 20 million m2, and on this basis, the annual production of more than 10 million plants, there are 300 in China, plant tissue culture. The annual output value has exceeded 20 billion yuan. According to the 300-day light day of the year, the plant tissue culture 16 h / d illumination time, the plant area of ​​20 million m2 of plants in the country, at least 300 million fluorescent lamps, need to invest 5 to 6 billion yuan, the annual electricity consumption of lighting The total amount needs at least 40 billion kW·h [4].