Working Principle And Classification Of Greenhouse

Working Principle And Classification Of Greenhouse

1. Greenhouses and their working principles

Greenhouses are special facilities that use transparent covering materials and environmental control equipment to create a local microclimate and promote crop growth and development. The function of a greenhouse is to create environmental conditions suitable for crop growth and development for efficient production. The solar radiation, mainly composed of shortwave radiation, enters the greenhouse through transparent materials, causing an increase in indoor ground temperature and temperature, and is converted into longwave radiation. Longwave radiation is then blocked by the greenhouse cover material, forming an accumulation of indoor heat and causing an increase in indoor temperature. This process is called the "greenhouse effect".

Greenhouses utilize the "greenhouse effect" to create a suitable environment for crop growth and increase crop yield by regulating indoor temperature during seasons when crops are not suitable for outdoor growth. But with the advancement of science and technology, greenhouse production has far exceeded the concept of "greenhouse effect". At present, high-tech technology can be used to automatically control and adjust various environmental factors in the greenhouse, including temperature, light, humidity, CO2 concentration, etc. According to the growth habits of crops and market needs, some or even completely break free from the constraints of the natural environment, and humans create a suitable environment for crop growth, producing high-quality and high-yield products to meet the needs of different consumer groups.

2.Types of Greenhouses

Production greenhouses are generally classified based on their transparent covering materials, main structural materials, and greenhouse performance.

1. Classification based on greenhouse transparent covering materials

(1) Glass greenhouse

A greenhouse with glass as the main transparent covering material. A greenhouse covered with single-layer glass is called a single-layer glass greenhouse, and a greenhouse covered with double-layer glass is called a double-layer insulated glass greenhouse.

(2) Plastic greenhouse

All greenhouses covered with transparent plastic are collectively referred to as plastic greenhouses. According to the properties of plastic materials, plastic greenhouses are classified into plastic film greenhouses and rigid board plastic greenhouses. Plastic film greenhouses are divided into plastic small arched greenhouses, plastic greenhouses, and large plastic film greenhouses based on their volume size (the latter is usually directly referred to as plastic film greenhouses or plastic greenhouses). To enhance the insulation of plastic film greenhouses, double-layer plastic films are often used to cover them, and greenhouses supported by frames of two layers of plastic films are called double-layer structure plastic greenhouses, A greenhouse with two layers of plastic film separated by inflation in the middle is called a double-layer inflatable greenhouse.

Hard board plastic greenhouses are divided into polycarbonate board greenhouses (including polycarbonate hollow board greenhouses and polycarbonate wave board greenhouses), fiberglass (including fiberglass reinforced polyester boards and fiberglass reinforced acrylic resin boards) greenhouses, etc. according to the different types of boards. It should be noted that if the transparent covering material of a greenhouse is not a single material, but is covered by two or more materials, the greenhouse should be classified according to the transparent covering material of the roof, and the final classification should be based on the material with the largest material area on the roof.

2. Classification based on the main structural materials of the greenhouse

(1) A bamboo and wood structure greenhouse is a greenhouse that uses bamboo and wood materials such as bamboo, bamboo sheets, and round wood as load-bearing structures for roof beams or indoor columns.

(2) The reinforced concrete structure greenhouse uses reinforced concrete components as the load-bearing structure of the greenhouse roof. Greenhouses with reinforced concrete components as indoor columns and bamboo and wood materials as roof structural components are still classified as bamboo and wood structured greenhouses.

(3) A steel structure greenhouse is a greenhouse that uses steel structural materials such as steel bars, steel pipes, steel plates, or profiles as the main load-bearing structure of the greenhouse.

(4) All load-bearing structures of aluminum alloy greenhouses are made of aluminum alloy profiles. The load-bearing components of the roof are aluminum alloy profiles, but greenhouses supported by steel structures such as beams, trusses, and columns are still classified as steel structured greenhouses.

5) Due to the continuous emergence of new building materials, greenhouses using these materials as load-bearing structures are also emerging, such as glass fiber reinforced cement (GRC) skeleton sunlight greenhouses, steel plastic composite material plastic greenhouses, etc.

3. Classification based on greenhouse performance

(1) Plastic shed

A single arch greenhouse made of plastic film as a transparent covering material is called a plastic greenhouse. Plastic greenhouse is the simplest type of greenhouse and currently has the largest number of greenhouse types in China.

(2) Sunlight greenhouse

It is a greenhouse with three insulated walls facing east, west, and south, and a curved skylight facing south. The biggest advantage of this type of greenhouse is its good insulation performance. Currently, it is the most widely available greenhouse style in the northern and northeastern regions of China.

(3)Multi-span greenhouse

A Multi-span greenhouse is a greenhouse that connects single span greenhouses. According to the roof form, Multi-span greenhouses can be divided into pointed roof greenhouses, circular arch greenhouses, serrated roof greenhouses, flat roof greenhouses, and shaped roof greenhouses. The biggest advantage of multi story greenhouse is its large indoor space, high space utilization rate, and high degree of mechanization. It is currently the most commonly used greenhouse style in developed countries and also the future development direction of greenhouse in China.