The principle of greenhouse lies in trapping the heat of sunlight to raise the temperature inside the greenhouse, thus meeting the growth needs of crops.
During the day, sunlight passes through the greenhouse film or glass and shines into the greenhouse. The heat from solar radiation is absorbed to increase the temperature inside the greenhouse. After the air temperature rises, the long - wave radiation heat reflected from the ground cannot escape through the greenhouse, which reduces heat loss and achieves the purpose of temperature increase. In this way, a suitable growth environment can be created for crops that are not suitable for the current season, thereby increasing crop yields.
Different crops have different temperature requirements for growth. In the past, farming was completely dependent on the weather. However, with the emergence of greenhouses, crops can grow and mature naturally even in cold weather, enabling us to enjoy a wide variety of fruits and vegetables throughout the year, enriching the public's dining tables. For farmers, the profit of off - season fruits and vegetables is considerable, which has led to the large - scale promotion and use of greenhouses.
In terms of time, the temperature changes with the rise and fall of the sun. In terms of space, the temperature also decreases or increases with differences in altitude, latitude and longitude. These temperature variations have different impacts on the growth and development of crops. Greenhouses consist of light - transmitting materials covering the framework and internal environmental control equipment, which can create a unique micro - climate inside the greenhouse and provide the temperature, humidity and other growth conditions required by different crops, achieving the functions of high - efficiency and high - quality production.
Natural ventilation can be adopted in greenhouses. The external wind pressure and the thermal pressure generated by the temperature difference inside the greenhouse promote the air flow inside the greenhouse. The air expands in volume and becomes lighter in mass when heated, rising and flowing upwards. After reaching the top, it diffuses around. After being cooled, its density increases and it returns to the ground, repeating this cycle to achieve the purpose of air circulation in the greenhouse.
The above is an introduction to the principle of greenhouses. Thanks to the emergence of greenhouses, crops can be free from harsh natural conditions, and the temperature suitable for crop growth can be artificially created. A large number of fruits and vegetables can be planted off - season to meet the needs of different consumers .
