In most parts of our country, the summer is hot and the temperature is relatively high. When the outdoor temperature is above 30°C, the temperature inside the greenhouse exceeds this 40°C. If only ventilation is used, and the temperature in the glass greenhouse is still above 35°C, normal production cannot be carried out in the greenhouse. It is necessary to cooperate in choosing other cooling methods to lower the indoor temperature. The daily greenhouse cooling methods used in production mainly include shading and cooling, which is the use of opaque or low light transmittance materials to shade and reduce light.
Preventing excess solar radiance from entering the greenhouse not only ensures that crops can grow normally, but also lowers the temperature of the greenhouse. Because of different shading materials and different installation methods, the greenhouse temperature can generally be lowered by 3℃~10℃. Shading methods include indoor shading and outdoor shading. The indoor shading system is a support system made by pulling metal wires or plastic mesh wires on the greenhouse frame, and installing the shading net on the film support line. Generally choose electric control or manual control.
The outdoor shading system is to install a shading framework outside the greenhouse framework, and install the shading net on the framework. The shading net can be driven by a curtain pulling mechanism or a film rolling mechanism to open and close freely. The shading net outdoor device has a good cooling effect and can directly block solar energy outside the greenhouse. Various types of shading nets can be used.
Transpiration cooling is the use of air unsaturation and the latent heat of water transpiration to cool down. When the moisture in the air has not reached saturation, the moisture will evaporate and become water vapor into the air. Together with the transpiration, the water will absorb the heat in the air, lower the air temperature, and increase the air humidity. In the process of transpiration and cooling, it is necessary to ensure the air activity on the surface and inside of the greenhouse, to discharge the high temperature and high humidity gas in the greenhouse, and to supplement the fresh air. Therefore, it is necessary to adopt the method of forced ventilation.
