Facility gardening semiconductor lighting and its scientific and technological problems in research and development

Facility horticulture To achieve sustainable development, there is an urgent need for comprehensive and comprehensive intelligent environmental control technology to overcome environmental adversity and create appropriate production conditions. Illumination is an important environmental factor for horticultural production. In order to obtain high yield and high quality agricultural products, all environmental factors related to agricultural biological production, including lighting, in the horticultural facilities during production must be artificially or intelligently regulated. The more accurate the environmental factors in the facility horticultural production system, the more accurate it is in line with the horticultural needs, which is more conducive to the potential of horticultural production. Throughout the development process of facility horticultural environment control technology, illumination is the last important environmental factor in horticultural facilities to achieve intelligent control after environmental factors such as temperature, humidity, CO2 concentration and airflow. The main reason is that before the appearance of a solid-state semiconductor electric light source such as a light-emitting diode (LED), the conventional electric light source as an actuator cannot adjust its light intensity and light quality components in real time, and cannot implement intelligent control. Nowadays, based on the good controllability and photoelectric advantages of LED light source, the use of LED fill light or artificial light environment control can well overcome the constraints of unsuitable lighting conditions on horticultural biological production, and is essential for ensuring high quality, high yield and stable production of facilities. .

Objective demand for artificial lighting in facility horticultural production

The regulation of light environment is physical regulation, ecological security, and less negative environmental effects. The regulation of greenhouse lighting environment has become the inherent requirement and objective demand of modern agricultural development to ensure the high yield, high quality, high efficiency and stable production of modern agriculture. Facility gardening as an environmentally controllable agricultural production method, the development of light environment control technology is its inherent requirement, but also an objective demand, mainly in two aspects. First, artificial replenishment of the greenhouse is necessary and urgent. There are two types of fill light methods, one is to enhance photoperiod and photosynthesis through visible light control (PAR); the other is to control morphology and quality through UV and FR. The necessity of artificial light supplementation in greenhouses is mainly based on the following points.

(1) Low light and illuminating stress. The severe production hazards often caused by weak light and light in the summer caused by rainy days in the rainy days and snowy days in winter, resulting in crop yield reduction or even no cropping.

(2) Haze weather. Since 2012, the frequency, duration and area of ​​impact of smog weather in China have been increasing year by year. The smog period lasts for 7 months (October to April). Under the smoggy weather conditions, the light intensity is reduced by 20%-90%, which seriously affects the photosynthesis of the crops, the flowering results, and is easy to cause pests and diseases, resulting in crop yield reduction or even harvest. Moreover, the frequent occurrence of smog in winter and spring coincides with the critical period of facility horticultural production, which aggravates the degree of damage and has a great impact on the income of vegetable farmers.

(3) Photoperiod regulation in high latitudes. In the high-latitude short-day sunshine area, it is urgent to adjust the photoperiod and increase the number of illumination hours.

(4) Long-day plant production needs. Producing long-day plants in areas with insufficient sunshine hours requires an increase in the number of hours of illumination to facilitate their completion of the growth cycle. In short, in order to overcome the light environment problem of the above-mentioned facilities horticultural production, artificial artificial light supplementation is a direct and effective way. Second, the complete artificial light facility produces light environment regulation. Accurate and intelligent light environment regulation is the decisive factor for high-quality, high-yield, energy consumption and production efficiency in artificial light plant tissue culture, plant factories, edible fungi factories and nursery factories. The necessity is very prominent. Through the regulation of light environment, crop shape can be improved, yield can be increased, and the content of beneficial chemicals can be increased according to human needs, the accumulation of non-profit substances can be reduced, the energy value and nutrient health value of agricultural products can be improved, and real-quality production can be realized.

The definition and connotation of agricultural semiconductor lighting

Traditional lighting is a visual application. It is an illumination system (illumination device) composed of artificial light or natural light that transmits light with specific luminosity and chromaticity requirements to the target object according to the scientifically designed distribution characteristics for human perception and information. Agricultural lighting is a lighting application method that includes both visual and non-visual functions. Traditional agricultural lighting refers to the use of photoelectric light sources to create suitable light environments or compensate for the lack of natural light in accordance with the production target requirements of various fields of agricultural production, and regulate the growth and development of agricultural organisms. And agronomic measures for reproduction. The emergence of LED has pushed agricultural lighting into a new stage of development, called agricultural semiconductor lighting, a new type of lighting that belongs to the category of modern agricultural lighting. Agricultural semiconductor lighting refers to the use of semiconductor electric light source and its intelligent control equipment. According to the requirements of the light environment requirements of agricultural organisms and the production targets in various fields of agricultural production, artificially creating suitable light environment or making up for the lack of natural light, regulating agricultural organisms. An agronomic measure for growth, development, and reproduction to achieve high-quality, high-yield, high-efficiency, and stable production targets. Characteristics of agricultural semiconductor lighting:

(1) The electric light source of agricultural semiconductor lighting is a modern electric light source such as a fourth-generation semiconductor solid-state light source-light-emitting diode;

(2) The spectrum of the electric light source can be precisely regulated, and the light intensity, light quality and photoperiod can be controlled in real time;

(3) It can meet the needs of light environment regulation and control in all fields of modern agricultural production, and achieve the goal of high yield, high efficiency, high quality and stable production;

(4) Agricultural semiconductor lighting includes both visual lighting and non-visual categories. Among them, the lighting of plants and edible fungi belongs to the former, and the lighting of livestock and poultry farming belongs to the visual category;

(5) Agricultural semiconductor lighting can completely break through the day and night and the interannual photoperiod laws of natural light illumination, and completely control the lighting conditions according to the demand;

(6) Light environment regulation needs to be coordinated with other environmental factors to control and comprehensively coordinate control. Facility Horticulture Semiconductor lighting is an emerging research branch of the facility horticultural engineering discipline. It is the most important component of agricultural semiconductor lighting and an important field for non-visual applications of semiconductor lighting. China's facility horticulture needs to vigorously develop semiconductor lighting technology and equipment to accelerate application process and industry. Development.

Facility gardening semiconductor lighting applications and its complexity

Facility gardening semiconductor lighting research production system is mainly facilities horticultural production system, biological species cover vegetables, flowers, seedlings, edible fungi, medicinal plants, etc., its application fields are diverse, various fields of biological forms are diverse, light environment demand is very different . In summary, the application areas of facility horticultural light environment regulation are as follows:

(1) Greenhouse fill light. In order to increase the photosynthesis yield of plants, increase the light intensity, and prolong the photoperiod of plant illumination, artificial light supplementation must be performed.

(2) Edible fungus factory. At present, the production of edible fungi is highly industrialized. Most edible fungi have low requirements on light intensity, but the requirements for light quality are harsh, the effect of yield quality is large, and the regulation of light environment is very important, and the application potential is huge.

(3) Plant factory. As the most advanced development stage of facility gardening, plant factories can be used for large-scale production of vegetables, seedlings (vegetable seedlings, rice, tobacco, etc.) and Chinese herbal medicines. Intelligent artificial light source and its light environment regulation play a decisive role in its production efficiency.

(4) Plant tissue culture. Plant tissue culture is an important means of rapid propagation and detoxification of seedlings. It is completely produced by artificial light. The demand for artificial light sources is extremely great, and the upgrading of electric light sources is very urgent.

Facility Horticulture Semiconductor lighting applications are complex and require systematic, multi-faceted, multi-scale research. One of the reasons is that agricultural bio-nutrition and growth and development have diversity and complexity. The response mechanism of agricultural organisms to light environment is different. The research methods are different, and it is necessary to systematically study one by one to reveal its photobiological laws. For example, plants use light energy, CO2 and water to form carbohydrates through chlorophyll photosynthesis and convert light energy into chemical energy. Microorganisms (for example, edible fungi) need to be decomposed by extracellular enzymes to obtain the required nutrients. Produces hyphae and fruiting bodies. The nutritional methods of the three agricultural organisms are fundamentally different, and the laws of light environment demand are very different. The second reason is that the agricultural production field is complex, the types of agricultural organisms are diverse and their forms are different, and the time and space requirements for the light environment are different. The third reason is that the quantitative properties of the light environment (light intensity and photoperiod), mass properties (light quality and spectrum), and electric light source luminescence characteristics (duty cycle, frequency) are many, and the biological effects need to be studied one by one. The superposition of the above three factors reveals the complexity and systemicity of plant photobiology research. Finally, there are many types of facility systems, and the characteristics of light environment and the law of change are different. It is necessary to carry out targeted light environment regulation.

Facility gardening semiconductor lighting urgently need to solve scientific problems

The study of the laws of agricultural biophotobiology is the basis of agricultural semiconductor lighting. As an emerging research field, the international start-up is late, and there are still many scientific problems in the research and development of facility horticultural semiconductor lighting. In summary, one of the scientific issues is photobiology. The light quality here refers to the type of light that has an effect on living things, including visible light, UV and far red light. (1) The biological function of light quality. The main research contents include the physiological metabolism, molecular biology and proteomics mechanism of the effects of light quality and complex light quality on the growth and yield and quality of plants and edible fungi; (2) the light quality adaptability between biological species and varieties. The difference mechanism is used; (3) the biological mechanism of interaction between light quality and other environmental factors; (4) the effective threshold and reference value (such as compensation point, saturation point and light stress threshold) of the facility biomass quantity attribute. The second scientific issue is adversity photobiology. The main research is to determine the response mechanism and agronomic significance of photosynthetic mechanism and metabolic system operation efficiency under monochromatic and composite light, strong light and continuous illumination.

Facility gardening semiconductor lighting urgently need to solve technical problems

Comprehensive analysis of the status quo of research and development of horticultural semiconductor lighting technology, the technical problems to be solved include three aspects:

(1) Establishing the lighting formula required for the growth and development, high quality and high yield of specific organisms in various production areas of facilities and horticulture;

(2) Develop an agricultural bio-light environment control strategy based on the lighting formula;

(3) Research and development of LED light source devices, lamps and computer intelligent control systems.

5.1 lighting formula and light environment control strategy

The light formula refers to a set of parameters that are aimed at high quality and high yield, and the types of light quality and quantity properties required for each stage of growth and development of specific plant species and varieties. The appropriate lighting formulas for specific organisms in the production and horticulture fields are different and specific, and need to be revealed one by one. The light environment control strategy refers to the space-time management method strategy of directly controlling and switching the light environment parameters through computer based on the high-yield and high-yield target, based on the illumination formula of each plant species and variety growth and development in the various horticultural production systems. It is necessary to establish a facility horticultural light environment control strategy. For example, the greenhouse light-filling strategy needs to comprehensively consider the natural light daily variation parameters, environmental parameters, crop photosynthetic physiological parameters, growth and development stages and luminaire properties, implement a cost-effective light-filling method to meet the light intensity, light quality and photoperiod requirements, and save energy and efficiency. The light environment control strategy has obvious spatial and temporal characteristics. The use of segmentation management is an optimal choice for facility horticultural production and has important practical significance. For example, the germination period, seedling stage, vegetative growth period and reproductive environment of horticultural crops have different light environment requirements. The growth stage of the tissue culture plants and the light environment requirements of the rooting stage are different, and the light environment requirements of the edible fungus mycelial growth stage and the fruiting body growth stage are different. . Therefore, based on LED semiconductor lighting technology, the management of the facility horticultural light environment needs to establish a dynamic real-time control strategy to maximize the production efficiency of light energy and biological resources, and avoid energy waste caused by blind ineffective lighting.

5.2 LED light source and lighting development

The development of special LED light sources and lamps is the core of the facility gardening semiconductor lighting, the most urgent. The development of LED light sources and lamps needs to follow the following principles.
(1) Principle of high light energy utilization. Develop reasonable spectral components, maximize the luminous efficiency of the LED light source, reduce the distance between the light source and the irradiated organism, reduce the light loss, and improve the light energy utilization efficiency;

(2) The principle of low cost. Cost is an important factor in determining the industrialization of greenhouse lighting industry in facilities, and it is necessary to dig deep into cost reduction technology;

(3) Ecological safety principles. On the basis of meeting the photosynthetic physiological requirements of the horticultural crops, it is suitable to improve the spectral composition of pure red and blue, increase the trace amount or a small amount of green light, and increase the visual health;

(4) Priority development of facilities LED high-value-added agricultural products special LED light source and lamps, which is conducive to the sales of lamps and cultivating leading enterprises. At present, the types of lamps already on the market include bulbs, lamps, panel lamps, downlights, strips, and light barriers. The indicators and performances of LED luminaire design include uniformity of illumination, plausibility of light quality, reliability of heat dissipation, suitability of LED chip power, effectiveness of illuminating surface design and sensory comfort.

5.3 intelligent control system

With the rapid development and mutual penetration of computer technology, network technology, communication technology, automatic control technology, bus technology, signal detection technology and microelectronic technology, semiconductor lighting has entered the era of intelligent control. This is especially true for agricultural lighting, where simple switching control has not been able to complete the need for complex regulation of the light environment. There are two main purposes for realizing the intelligentization of the lighting control system: one is to improve the control and management level of the lighting system, to reduce the maintenance and operating costs of the lighting system; the second is to save energy and improve light efficiency. In general, the lighting control system consists of sensors, control circuits, control software, control PLCs or computers. The main functions of the agricultural semiconductor lighting intelligent control system include two aspects. First, control the light quality, light intensity and photoperiod of the LED luminaire; second, control the spatial position and movement rate of the luminaire.

Conclusion

Facility gardening semiconductor lighting related scientific and technical issues to solve the ultimate goal is to provide services for research and development and industrialization services for facility horticultural production practices. The goal of facility gardening semiconductor lighting:

(1) Energy conservation and improve the efficiency of light energy utilization of agricultural organisms;

(2) High quality and high yield, obtaining higher production efficiency and biomass, and improving energy substances or health beneficial substances;

(3) Stabilizing production and reducing light environmental adversity;

(4) Visual health, does not harm the visual health of production personnel.

At present, facility horticultural semiconductor lighting is in full swing and development is in full swing. However, based on the complexity of facility horticultural production, facility horticultural semiconductor lighting still has a long way to go in terms of scientific laws and technology research and development. However, there are reasons to believe that in the next 5-10 years, China's facilities and horticultural semiconductor lighting science and technology research and development and application will make great progress, and will also greatly promote the development of facilities and horticultural semiconductor lighting industry and discipline.