Main technical performance indicators of greenhouses

1. The light transmission performance of the greenhouse

2. Insulation performance of greenhouse

The greenhouse is a lighting building, and its The quality of light transmittance directly affects the formation of photosynthetic products of indoor crops and the level of indoor temperature. Light transmittance is one of the most basic indicators to evaluate the light transmittance performance of a greenhouse. It refers to the percentage of the amount of light penetrating into the greenhouse to the amount of outdoor light. The higher the light transmittance, the better the light and heat performance of the greenhouse. The light transmittance of the greenhouse is limited by the light transmittance of the light-transmitting cover material of the greenhouse and the shadow rate of the greenhouse skeleton, and the light transmittance of the greenhouse changes at any time with the difference of the solar radiation height in different seasons. In summer, the outdoor solar radiation is strong. Even if the light transmittance of the greenhouse is small, the absolute value of the light intensity entering the greenhouse is still relatively high. To ensure the normal growth of crops, appropriate shading facilities are still necessary. However, in winter, due to the weak outdoor solar radiation and the low solar height angle, the light transmittance of the greenhouse has become a direct factor in crop growth and selection of crop varieties. Generally, the light transmittance of glass greenhouse is 60% 70%, multi-span plastic greenhouse 50% 60%, and solar greenhouse can reach more than 70%. heating and energy consumption is the main obstacle to the operation of greenhouse in winter. Improving the thermal insulation performance of the greenhouse and reducing the energy consumption are the most direct means to improve the efficiency of greenhouse production. In addition to the thermal resistance of the greenhouse envelope, the thermal insulation ratio of the greenhouse is the most basic indicator. Greenhouse insulation ratio refers to the ratio of the total coverage area and ground area of ​​the greenhouse enclosure structure with larger thermal resistance to the coverage area of ​​the greenhouse with light-transmitting materials with smaller thermal resistance. The greater the insulation ratio, the better the insulation performance of the greenhouse. Generally, the thermal insulation ratio of greenhouse is less than 1.0, but the thermal insulation ratio of some solar greenhouse may be greater than 1.0, so the thermal insulation performance of solar greenhouse is far better than other greenhouse. The greenhouse is a high-input and high-output agricultural facility, and its one-time investment is several times higher than that of open field production. Ten times or even hundreds of times, the length of its service life directly affects the annual depreciation cost and production efficiency, so the greenhouse construction must consider its durability. In addition to the aging resistance of greenhouse materials, the factors affecting the durability of greenhouse are also related to the carrying capacity of the main structure of the greenhouse. In addition to its own strength, the durability of the light-transmitting material is also manifested in the degree of attenuation of the light transmittance of the material over time. The attenuation of the light transmittance is often the decisive factor affecting the service life of the light-transmitting material. The carrying capacity of the main structure of the designed greenhouse is directly related to the reproduction period of the maximum wind and snow load. Generally, the service life of a steel structure greenhouse is more than 15 years, and it is required to design the wind and snow load with the maximum load once in 25 years. Because the greenhouse has been operating in a high temperature and high humidity environment for a long time, the surface anticorrosion of the components has become another important factor affecting the service life of the greenhouse. For steel greenhouse, the main structure of the force is generally thin-walled steel, which has poor corrosion resistance. Hot-dip galvanized surface anti-corrosion treatment must be used in the greenhouse. The thickness of the coating reaches 150200; more than xm, it can be used for 15 years. life.