Ventilation System Features
These features can be listed as follows.
- The ventilation system must not create an air breeze on the plants. Air movement should be in the space above the plants. In contrast, adequate air exchange should be ensured at the location of the plants.
- Fresh air entering the greenhouse must not hit the plants directly.
- The ventilation element must be intact and be able to close securely. Thus, heat loss is less with air exchange.
- Aerators must be waterproof.
- Ventilation should not be affected by storm. The ventilation system must not be opened or closed by external influences.
- Ventilation openings must be large enough.
- The ventilation system should not be able to create technical problems in the enterprise and should be able to open and close with a little force.
Number of Air Change
The effect of ventilation in the greenhouse is determined by the number of air changes in the greenhouse. This number of changes is to know how many times the greenhouse air will change in one hour. This number is between 30 – 40 is sufficient for a good ventilation of the greenhouse, but these values are given in Table 1.1.
The most important factor in the air exchange rate required for ventilation depends on the difference between the temperature of the air inside and outside the greenhouse as well as the sum of the window areas and their distribution to the greenhouse surfaces.
Greenhouses are ventilated by ventilation openings placed on the side walls and roofs of the greenhouses. The windows that are effective in ventilation are roof windows. As in our country, especially in greenhouses covered with plastic, the lack of ventilation windows on the greenhouse roof generally reduces ventilation considerably. In this case, even if the window area placed on the side wall increases too much, it cannot increase the ventilation to the desired level.
Greenhouse production companies, who are aware of the importance of roof ventilation, are provided with roof windows on both sides of the ridge, roof ventilation is carried out by moving all the roof elements down or up, and roof ventilation is collected by gathering the roof elements aside.
Windows and ventilation openings provide good ventilation in the greenhouse when opened, but no openings when closed. Hot air in the greenhouse must not come out of the closed window openings. In this way, the use of excess fuel in the greenhouse in cold weather is prevented from increasing fuel costs. The effect of the wind on the ventilation system is great. In areas where the wind is constantly blowing, the size of the ventilation openings can be reduced as the air movement caused by the wind will increase in the greenhouses. This increases wind resistance.
Table 1.1. Number of air changes in greenhouses
Condition of the ventilation: Number of changes
Greenhouse with closed windows: 0,6-2
Bad ventilation: 20-40
Good ventilation: 40-50
Very good ventilation: more than 50
Greenhouse ventilation mechanisms can be installed in 4 different ways as automatic or manual from the side and automatic or manual from the top. The cultivated plant species should be designed and projected very well according to the greenhouse type and regional climate. The maximum yield-oriented studies are essential for getting to know the plants and climate well and to have a quality greenhouse structure.
Upper ventilation system works with rack and pinion system. On both sides of the hill ridge, the swing arms are made of 40 x 30 profiles, 2 m wide along the ridge, in the form of butterflies. The system is opened and closed by placing rack and gear to the mm pipe which is used as shaft placed in specially made roller bearings and this system pushes the window.
One motor will be used for each window and the limit switches are on the motors. The rack and pinion gears to be used are placed on the shaft with the rack.
The rack and pinion casing is made of powder-cast steel and is highly wear-resistant. Galvanized material is used as material.