1. The principle of adapting measures to local conditions
Different countries and regions have different characteristics in their geographical location, natural conditions, climate characteristics, social and economic conditions, planting habits, and cultivation methods. The selection of the form of the greenhouse, the determination of the structural scheme, the selection of building materials, the material and thickness of the thermal insulation layer, the construction cost and operating costs of the greenhouse, etc., must be determined according to the specific local conditions.
2. The principle of saving energy
Energy conservation is a long-term national policy for both developed and developing countries. Large-scale multi-span heated greenhouses in developed countries have been developed because of their high energy consumption and higher output; although the United States is a country with sufficient energy, it does not choose to build a large number of greenhouses in the colder northern regions, and its greenhouses are relatively concentrated in In the warm southern regions such as Florida, California and Arizona, the United States imports a large number of vegetables from Mexico in winter, which is based on energy considerations. Energy is scarce and expensive in my country, especially in the vast cold regions of the Three Norths, where large-scale multi-span heated greenhouses cannot be used as the main agricultural production facilities in the short term. In terms of greenhouse design, it is necessary to consider the penetration of more sunlight and strengthen thermal insulation measures to reduce the energy consumption of winter operation and thus reduce operating costs.
3. The principle of safety and durability
The greenhouse must not only ensure the environmental conditions required for the growth of crops, but also bear various loads that may be encountered, such as the self-weight of the structure, the hanging weight of the crops, the wind load, the snow load and the construction load. The structural calculation should fully consider various unfavorable loads. The load combination is used to maintain sufficient strength, stiffness and stability under the possible loads during construction and operation, and full attention should be paid to the corrosion resistance and rust resistance of metal components. Generally speaking, a permanent greenhouse should be able to be used for more than 15 years.
4. The principle of cost saving
On the premise of satisfying the use function, the design and construction of the greenhouse must first make full use of local building materials to reduce material costs and transportation costs, thereby reducing the initial investment. For the relationship between initial investment and operating costs, technical and economic analysis and comparison should be made, and the principle of obtaining better economic benefits should be taken as the principle.
5. Principles of environmental protection and sustainable development
When designing a greenhouse, improve its lighting and thermal insulation performance as much as possible to reduce fuel consumption and thus reduce air pollution. This is not only a requirement for energy conservation, but also for environmental protection considerations. Full attention should be paid to the heating method of the greenhouse. For larger-scale greenhouse groups, when heating is necessary, central heating should be used as much as possible. Otherwise, clean energy such as liquefied petroleum gas should be used as much as possible. Electric heating can also be considered.