What Is a Commercial Greenhouse?
Greenhouses, also known as greenhouses, refer to rooms with facilities for cold protection, heating, and light transmission for the cultivation of warm plants in winter. In the unsuitable season for plant growth, it can provide the growth period and increase the yield. It is mostly used for plant cultivation or seedling cultivation of vegetables, flowers, forests and other plants in the low temperature season. A greenhouse is a building that controls or partially controls the environment in which plants grow. Mainly used for non-seasonal or non-regional plant cultivation, scientific research, additional breeding and ornamental plant cultivation. [1]
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- 1. a warm house.
- Chinese·
Greenhouse Introduction
- Greenhouse (15 photos)
- Greenhouse is a building with lighting covering material as all or part of the envelope structure. It can be used for cultivating plants in winter or other unsuitable seasons for open-field plants.
Greenhouse History Origin
- The origin of the greenhouse can be traced back to the earliest period of Qin Shihuang. According to the scholar Wei Hong's "Preface to the Official Book of Luding," the book "Qin is burning, I fear that the world will not change from the law, and those who come will worship as Lang. Seven hundred people are closely planted in the middle temperature of Laoshanling Valley. "He lived for more than two hundred years, and his records must be based on word-of-mouth history. [3]
- Tang Shi scholar Yan Shigu said in the commentary of "Hanshu · Volume 88 · Rulin Biography 58th" that "where is the wet soup in Xinfeng County today, No. Confucianism Village". Wei Hong said that "the middle temperature of the Laoshanling Valley" further consolidated Wei Hong's credibility. Wei Hong's record about Qin Shihuang revealed a valuable piece of agricultural technology information. That is, during the Qin Shihuang period, the Chinese had invented the greenhouse technology. [3-4]
Greenhouse main classification
- 4-story greenhouse sunlight panel
- According to the model, the greenhouse can be divided into GLP622 single building / multi-building type 6 type 8 type GKW7430 film GSW8432 / 8430/825 greenhouse PC board greenhouse.
- Greenhouses can be divided into thin film greenhouses, glass greenhouses, and plastic plate greenhouses by material.
Greenhouse plastic material
- Large-scale multi-story plastic greenhouses are a type of greenhouse that has emerged and developed rapidly in recent decades. Compared with glass greenhouses, it has the advantages of light weight, small amount of framework materials, low shading rate of structural parts, low cost, and long service life. Its environmental regulation ability can basically reach the same level as glass greenhouses. Plastic greenhouse users accept The capacity is far higher than glass greenhouses worldwide, and has become the mainstream of modern greenhouse development.
- Plastic greenhouse structure
- Overall dimensions of plastic greenhouses
- Such greenhouses have different structural sizes in different countries. But in general, the span of general greenhouses is 6m ~ 12m, the open space is about 4m, and the eaves are 3 ~ 4m high. For greenhouses with natural ventilation as the main component, the maximum width of the greenhouse should be limited to 50m, preferably 30m when using side windows and ridge windows. For greenhouses with mechanical ventilation, the maximum width of the greenhouse can be limited. Expand to 60m, but it is best to limit it to about 50m. For the length of the greenhouse (from the perspective of convenient operation), it is best to limit it to 100m, but there is no strict requirement.
- 2. The main structure
- The main structure of plastic greenhouses generally uses hot-dip galvanized steel pipe as the main load-bearing structure, which is produced in factories and installed on site. Due to the light weight of the plastic greenhouse and its weak resistance to wind and snow loads, full consideration must be given to the overall stability of the structure. Generally, vertical diagonal braces should be installed in the second span or second room of the room. Consideration must also be given to providing necessary space support on the envelope structure and on the roof. It is best to have diagonal supports (stayed rods) anchored to the foundation to form a space force system.
- The main structure of a plastic greenhouse must be capable of resisting at least level 8 wind, and generally requires a level of wind resistance of level 10.
- The snow load carrying capacity of the main structure should be determined according to the actual snowfall conditions in the construction area and the winter use of the greenhouse. For use in the north, the design snow load should not be less than 0.35kN / m2.
- For annual operation of plastic greenhouses, multiple load factors such as equipment weight, plant lifting, and maintenance should also be considered.
Greenhouse glass material
- Glass greenhouse is a greenhouse with glass as transparent covering material.
- Design requirements
- In foundation design, in addition to meeting the requirements of strength, it should also have sufficient stability and ability to resist uneven settlement.
- Zhongnong Scenic Sunlight Greenhouse
- Independent foundation. Reinforced concrete is usually used.
- Strip foundation. Masonry structures (bricks and stones) are usually used, and construction is also carried out on site. A reinforced concrete ring beam is often installed on the top of the foundation to install embedded parts and increase the strength of the foundation.
- The steel structure mainly includes : the bearing structure of the greenhouse and the support, connection pieces, and solid pieces provided to ensure the structural stability.
- The design of glass greenhouse steel structure in China is mainly based on the greenhouse design codes of the Netherlands, Japan, and the United States. However, issues such as structural strength, structural rigidity, structural integrity, and structural durability must be considered in the design.
- Classification: Glass greenhouses can generally be divided into text-type and large-roof type. Most of them use tempered glass on the top, ordinary float glass or insulating glass around them. There are also sunlight greenhouses on the top of glass greenhouses, and glass around.
Greenhouse performance
- Light transmission
- The greenhouse is a daylighting building, so the light transmittance is one of the most basic indicators for evaluating the light transmission performance of the greenhouse. The light transmittance refers to the percentage of the amount of light that penetrates into the greenhouse and the amount of outdoor light. The light transmittance of the greenhouse is affected by the light transmittance of the light-transmitting cover material of the greenhouse and the shadow rate of the greenhouse skeleton. Moreover, the light transmittance of the greenhouse also changes at any time with the different angles of solar radiation in different seasons. Greenhouse light transmittance has become a direct influence on crop growth and selection of crop varieties. Generally, the number of plastic greenhouses is 50% ~ 60%, the light transmittance of glass greenhouses is 60% ~ 70%, and sunlight greenhouses can reach more than 70%.
- Thermal insulation
- Heating energy consumption is a major obstacle to the operation of greenhouses in winter. Improving the thermal insulation performance of the greenhouse and reducing the energy consumption are the most direct means to improve the production efficiency of the greenhouse. The insulation ratio of a greenhouse is a basic indicator for measuring the insulation performance of a greenhouse. Greenhouse insulation ratio refers to the ratio of the area covered by the transparent material of the greenhouse with a small thermal resistance and the area covered by the greenhouse envelope structure with a large thermal resistance. The larger the insulation ratio, the better the insulation performance of the greenhouse.
- Durability
- Greenhouse construction must consider its durability. Greenhouse durability is affected by factors such as the aging resistance of greenhouse materials and the carrying capacity of the main structure of the greenhouse. In addition to its own strength, the durability of light-transmitting materials is also manifested in the fact that the light transmittance of the material decreases continuously with time, and the degree of attenuation of the light transmittance is a decisive factor that affects the life of the light-transmitting material. The service life of general steel structure greenhouses is more than 15 years. The design wind and snow load are required to meet the maximum load once in 25 years; the simple greenhouse with bamboo and wooden structure has a service life of 5 to 10 years, and the design wind and snow load is used to meet the maximum load once every 15 years.
- Due to the long-term operation of the greenhouse in high temperature and high humidity environments, the surface corrosion of components has become one of the important factors affecting the service life of the greenhouse. Steel structure greenhouse, the main structure of the force is generally thin-walled steel, and its own corrosion resistance is poor. In the greenhouse, the hot-dip galvanized surface must be used for anti-corrosion treatment. The thickness of the coating is 150 ~ 200 microns, which can guarantee 15 years of use life. For greenhouses with wooden structures or reinforced welded truss structures, surface anticorrosive treatment must be guaranteed once a year.
Greenhouse type
- Safety
- Environmentally-safe greenhouse is a closed type of physical plant protection technology, environmental control technology, and biological control technology. It can control plant diseases and insect pests without using pesticides or other chemicals, and can protect plants from severe weather and physiological obstacles. Plant breeding facilities. Environmentally safe greenhouses are mainly divided into two categories: physical plant protection greenhouses and environmentally controlled greenhouses. The former focuses on the physical control facilities for plant diseases and insect pests during the full growth period. The latter is a greenhouse that controls diseases and insect pests, physiological obstacles, and growth environment regulation.
- Environmentally safe greenhouse
- The physical plant protection greenhouse is mainly designed based on the physical plant protection technology integration system as the core of the plant protection facility, that is, the soil pest control is designed as a soil continuous cropping barrier electric treatment mode, and the aerial part disease control on the ground is set as a greenhouse electric defogging and disease prevention and promotion system The established space electric field control mode, flying pest control is set to color, light double electric trapping and insect net-combination mode, red spider and other mites are biological control mode or perilla anti mite mode.
- Controlled
- Environmentally controlled greenhouses are based on physical plant protection greenhouses, supplemented by temperature, light, and carbon dioxide concentration control modes. These greenhouses not only ensure pesticide-free control of plant diseases and insect pests during plant growth, but also ensure continuous cloudy or It can still grow or protect seedlings under extreme weather conditions. Auxiliary facilities for growing environment include hot air stove or soil heating line or wet curtain, space electric field generating system, supplementary light, and carbon dioxide increasing application system. Among them, the space electric field generating system has the function of regulating photosynthesis of plants in addition to preventing airborne diseases. , Can enhance the photosynthesis intensity of plants in low light environment. [5]
Greenhouse solarium
- The front slope is covered with heat insulation at night, and the east, west, and north sides are single-slope plastic greenhouses that are enclosing walls, collectively referred to as sunlight greenhouses. Its prototype is a single-slope glass greenhouse, and the front-slope light-transmitting covering material uses plastic film instead of glass to evolve into an early sunlight greenhouse. Solar greenhouses are characterized by good thermal insulation, low investment, and energy conservation, and are very suitable for use in less developed rural areas in China.
- Solar greenhouse performance
- The light transmittance of energy-saving solar greenhouse is generally above 60% ~ 80%, and the temperature difference between indoor and outdoor can be maintained above 21 ~ 25 degrees Celsius.
- 1. Solar greenhouse lighting
- On the one hand, solar radiation is the most important energy source to maintain the temperature of solar greenhouses or maintain heat balance; on the other hand, solar radiation is the only light source for photosynthesis of crops.
- 2. Solar greenhouse insulation
- The thermal insulation of solar greenhouse is composed of two parts: thermal insulation envelope structure and movable thermal insulation quilt. The thermal insulation material of the front slope should be made of flexible materials so that it can be easily stowed after sunrise and put down at sunset.
- The research and development of new front roof insulation materials are mainly focused on the requirements of easy mechanized operation, cheap price, light weight, aging resistance, water resistance and other indicators.
- The solar greenhouse is mainly composed of three parts: the surrounding wall, the rear roof and the front roof, referred to as the "three elements" of the solar greenhouse. The front roof is the entire daylighting surface of the greenhouse. During the daylight hours, the front roof is only covered with plastic film. When the light diminishes, cover the plastic film with movable insulation in time to strengthen the insulation of the greenhouse.
- The solar greenhouse can also be equipped with a top window system, a roll film system, etc.