Interpretation of thermal insulation and cold protection technology in greenhouse
First, the shed-type structure and direction are the most critical. Sheds are mostly arc-shaped, and the better direction of the shed is to sit north to south, and the east-west direction is better. In winter, they can fully receive the sunlight and increase the temperature in the shed. It is also conducive to ventilation, reducing humidity in the shed and reducing pests and diseases. The size of the shed is better than the standard 8-meter shed, and the length of the shed should not exceed 45 meters. In the structure of the greenhouse, the spacing of the steel pipes is preferably 80 cm, and the spacing should not be too wide, otherwise the shed membrane is easily blown off by the wind. If it is a multi-span shed, it is required to install drainage grooves in the multi-span position to prevent rainy rain from dripping into the shed from the position of the multi-span, increase the humidity in the shed, and reduce the temperature in the shed. When building a shed, the most taboo is cutting corners. In the structure of the greenhouse, the distance between the steel pipes cannot be more than one meter. If the distance between the steel pipes exceeds one meter, it is easy to cause the membrane of the greenhouse to be rolled up and down by the wind, and even blown away by the strong wind. At least the requirements.
2. Cover the inner membrane. For a greenhouse with a width of 8 meters, it is recommended to cover the inner membrane when the greenhouse is relatively high. The distance between the inner membrane and the outer membrane is better than 25cm, which ensures the air insulation between the inner membrane and the outer membrane, and reduces the effects of air convection and heat dissipation. The disadvantage of capping the inner membrane is that the inner temperature of the inner membrane is high and the external temperature is low. Due to the temperature difference, it is easy to form water droplets in the inner membrane, which increases the humidity in the shed and increases the incidence of vegetables in the shed.
Cover with non-woven fabric. Compared with the inner film, this measure can significantly reduce the indoor humidity of the shed and effectively reduce the occurrence of diseases. At the same time, the non-woven fabric has a significant thermal insulation effect, which can increase the temperature of the greenhouse by 3-5 ℃. Since the non-woven fabric is easy to pull and easy to manage, it brings a lot of convenience to the greenhouse management. Please note: the non-woven fabric is better suspended in the peripheral position of the shed.
Fourth, use heating equipment such as heaters, air conditioners, radiators, etc. Where possible, heaters can be purchased. The heaters are divided into 1000 watts, 1500 watts, 2000 watts, and 2500 watts according to the power. For an 8*30m greenhouse, four 1000 watt heaters can be used for heating. Two of the heaters are placed at the two ends of the field to blow warm air to the middle of the field, and the other two are located at the middle of the sky to blow warm air to the two ends of the field, which can effectively increase the temperature in the shed by 2-5°C. In addition, we can also use heating equipment such as radiators in the north. Because the heating equipment is more expensive, these heating equipment are mostly used in greenhouse seedlings and cultivation of valuable flowers.
Five, use high-power bulbs. When the bulb is used at night, it is better to use a large bulb power of 1000 watt bulb, which can effectively avoid the occurrence of frost damage. Generally speaking, 4-6 bulbs are used in the 8*30m greenhouse, which can improve the air temperature by 2-3℃
Sixth, smoking measures. On a sunny evening, due to the blue sky and no clouds, the heat in the field can be dissipated in the form of heat radiation. On a cloudy day, because there are clouds in the sky, it acts as a thin film, and the heat in the field will not be radiated. In this case, we recommend using the smoke method on a sunny day to prevent frost damage. The smoked raw material can be added with red coal briquettes and sawdust, which requires the sawdust to be half dry and half wet. In this way, there will be no open flames in the sawdust, which can effectively produce dense smoke, but it is worth noting that the amount of smoked smoke should not be too thick; the crops planted next to the sawdust are most likely to be affected by smoke, so it must be prevented from occurring. . Also pay attention to safety to avoid fire or harm to people. In addition, it can be used in combination with fumigant. Common bactericidal fumigant and insecticide fumigant can be used, and it is easy to control. It also has the effect of preventing insects and curing diseases. You can get twice the result with half the effort.
Seven, lighting candles or burning firewood, the effect is more obvious. When the temperature reaches zero, two open flames are burned at both ends of a 30*8m shed, which can effectively increase the temperature and the air temperature in the shed by 3-5 ℃. Burning candles, it is more appropriate to place about 30 candles in a 30*8m shed, so that the air temperature in the shed can be increased by 2-3 ℃. But we must prevent fires. Put the open flame on the ground where the tomatoes are not cultivated, do not get too close to the tomatoes, so as not to burn the tomatoes.
Eight, spray warm water. The water temperature is more suitable at 25-28℃. Timing of spraying warm water: When none of the above methods can keep the temperature in the shed above 3-5℃, use this method to solve the emergency needs. However, this will increase the humidity of the air, so if the weather temperature is higher than 8°C the next day, you can ventilate in time to remove the moisture.
The above measures are not used in isolation. Reasonable arrangements should be made according to local conditions, and reasonable arrangements should be made on the basis of making full use of existing resources. While doing the above work, we should pay attention to the airtightness of the greenhouse itself. If the airtightness is not good, then the above measures are the best. As long as the wind enters, the plant will be damaged by cold or freezing, and it will not be able to perform its proper thermal insulation and cold protection. effect.