Greenhouse is widely used because of the high price of out-of-season vegetables, considerable profits and mature outdoor picking. Even in the cold winter, the greenhouse is very warm. Everyone should not only think about why the temperature in the greenhouse is so high, but also think about the heat preservation principle of the greenhouse. Let's have a look.
For solar radiation, plastic greenhouses and glass are almost "transparent" and most solar radiation can enter. But for long-wave radiation on the ground, plastic greenhouses and glass are not "transparent", and long-wave radiation rarely penetrates. In this way, the greenhouse allows the external solar energy to enter the room continuously, but the indoor heat is rarely lost, thus playing a role in regulating the temperature.
So the sun shines into the greenhouse through the film, and the temperature is firmly locked by the film, so the temperature is relatively high. The surface itself has a temperature. Because of the barrier of the film, the cold air outside can't get in and can't touch the indoor air, so the temperature won't drop. The function of the membrane is to let in only sunlight and not air, so the indoor temperature is much higher than the outdoor temperature.
With the maturity of greenhouse technology in recent years, the types of greenhouses are increasing day by day, and their functions are beginning to be refined. According to the function, there are ornamental greenhouses, entertainment greenhouses, catering greenhouses and experimental greenhouses. Of course, the most important greenhouse is used to grow vegetables. Let's take a look at the types of greenhouses divided by materials.
1, glass greenhouse
Why is the temperature high in the greenhouse? Principle of heat preservation in greenhouse.
Its covering material is mostly transparent glass, and its light transmittance is very good, even reaching 70%. The skeleton is generally made of galvanized steel pipe or aluminum alloy light steel, which is very inconvenient to install and maintain, and the economic benefit cannot be effectively guaranteed.
2. Plastic greenhouse
Why is the temperature high in the greenhouse? Principle of heat preservation in greenhouse.
Widely used in southern China, mainly for gardening facilities. Plastic greenhouses are covered with plastic films, and most of them are cement-reinforced mixed columns. It is a single-span arched roof greenhouse with no heating, and its main function is to be warm in winter and cool in summer.
3. Plastic solar greenhouse
Why is the temperature high in the greenhouse? Principle of heat preservation in greenhouse.
This is a traditional greenhouse in northern China, which has developed rapidly in recent years. It has the advantages of light weight, less skeleton materials, long service life, high production efficiency and strong ability to adjust the environment. This type of greenhouse is easily accepted by the whole world and almost becomes the mainstream of today's development.
4. Movable roof greenhouse
This kind of greenhouse is widely used in areas with mild climate and no snow. It has an automatic curtain drawing system, which can be reasonably controlled according to outdoor conditions, which can fully reduce energy costs and improve efficiency to a certain extent.
There are many kinds of greenhouses. With the development of technology, there will be more and better products in the future, which will bring great convenience to agricultural production.