The process of venting the greenhouse is the main factor that affects not only the yield, but also the viability of the crops inside it. There are several ways to air the greenhouse: automatic and manual. By hand include vents, sections or greenhouses with an opening roof. Manufacturers offer various forms of greenhouses, the design of which consists of a metal frame covered with a polycarbonate with an opening roof. The use of thermal drives for greenhouses greatly simplifies the process of ventilation and completely eliminates the human factor.
- Automatic airing of greenhouses: how it works, or What is a thermal drive for greenhouses
- Types and principle of automatic ventilation of greenhouses
- Electronic Thermal Drive
- The principle of the plate made of different metals
- Features of the design based on hydraulics or pneumatics
- The advantages of using automatic ventilation systems
- How to choose a thermal drive system for the greenhouse
- Features of installation of the thermal drive in the greenhouse
Automatic airing of greenhouses: how it works, or What is a thermal drive for greenhouses
To make the plants in the greenhouse feel good, It is necessary to observe the correct temperature conditions, humidity and fresh air. To solve these problems, you should install the vents with closers for greenhouses. With their help, you can adjust the microclimate in a covered garden. With proper ventilation in the greenhouse, harmful insects and microorganisms will not multiply, and the temperature will be maintained at the optimum rates for the plant.
That this system worked harmoniously and without delay, window leaves must also be equipped with machines for ventilation of greenhouses. Due to the ability of warm air to rise upwards, the vents should be placed in the upper part of the greenhouse. Their number is on average 2-3 per 6 m long structure. It should be remembered that they should be placed over the entire area approximately evenly, to ensure the same movement of air flow, to prevent drafts and the slam of frames when a gust of wind.
You can do without the automatic ventilation of greenhouses, but its presence will greatly facilitate the work of the gardener and allow you to do other work.
Types and principle of automatic ventilation of greenhouses
The principle of operation of any automatic ventilation of greenhouses with thermal drive is based on opening and closing the vents as a result of temperature indicators in the room. There are several types of devices for ventilation of greenhouses. Each of them differs in the physical principle underlying the operation of the device, and has its own advantages and disadvantages.
Electronic Thermal Drive
The system consists of fans located in the upper part of the greenhouse, and a thermal relay with sensors controlling their operation. This is one of the most convenient and effective ways to regulate temperature.
The advantages of using electronic thermal drive are:
- rationality;
- precise temperature control, which is not inert;
- wide range of power that fits any size of greenhouses;
- ability to use in greenhouses of any design.
The disadvantages of an electric ventilator for greenhouses are its complete dependence on electricity and its uninterrupted supply. To eliminate this disadvantage,You can install a backup power source in the form of a battery, generator or storage of solar panels.The principle of the plate made of different metals
It is much less common to use an auto-ventilator for a greenhouse, the principle of which is based on the ability of different metals to react differently to temperature fluctuations. Such a device is called a bimetallic system. It consists of two plates consisting of metals with different linear expansion coefficient. When heated, the plates bend in one direction and open the window, when cooled - in the other, closing it.
Advantages of this system:
- full autonomy and independence from power sources;
- ease of installation;
- can be operated for a long time;
- cheapness.
- inertness. In case of insufficient heating, the window will not open;
- low power It is adapted only for light frames;
- problematic selection of metals capable of expanding at the right temperature for plants.
Features of the design based on hydraulics or pneumatics
The system with a thermal drive for an automatic greenhouse is based on a hydraulic or pneumatic principle of operation. The difference of these principles in the working body: fluid or air. The system can be made independently or bought in a store.
The device consists of a cylinder filled with a special fluid, and a rod that moves under the force of expansion or contraction of this fluid. Liquid at a temperature of 23 degrees begins to expand and pushes the rod with a force of more than 20 kg, opening the window. The system should close under its own weight as the rod moves. If the window has a structure that needs to be closed, then either a spring or a similar mechanism of inverse action is proposed for this.
Such a system has several advantages:
- reliability and durability;
- power supply independence;
- easy attachment to the frame. All you need is a screwdriver or a screwdriver;
- sufficient power for any type of frame.
- inertness of the process. With a sharp decrease in temperature, the closure is slow;
- temperature is monitored only at the place of attachment of the system;
- high cost, therefore not economically viable for small greenhouses.
A system with pneumatic-hydraulic principle of operation can be made with your own hands. To do this, we need two cans with a volume of 3 liters and 1 l. In a large container pour 0.8 l of water and roll it with a tin lid. In the cover we make a hole for a metal tube with a diameter of 5-8 mm, insert it (the end of the tube should be 2-3 mm from the bottom) and seal the hole. We perform the same procedure with another can, only in this case it is necessary to take a capron lid. Banks are connected with a pipe from a dropper with a length of 1 m. We received a pneumatic-hydraulic siphon. Place it inside the greenhouse on a window with a horizontal axis of rotation, as shown in the figure.It is necessary to fix a wooden bar on the outer bottom side of the window as opposed to an empty cylinder of a smaller volume. From the outside over the axis of the window we fix the stop.1 - bar counterweight; 2 - window frame; 3 - the central axis of the frame; 4 - fastening of small capacity to the frame.
The principle of operation is based on the expansion of air with increasing temperature in a larger bank. The air pushes the water, pouring it into a smaller jar, which opens the window. When the temperature decreases, water is sucked into its original position, and the window is closed due to the counterweight. This system has several advantages:
- energy independent;
- simple and cheap.
- cumbersome design;
- in a large container must periodically pour water to replace evaporated;
- This method is used only for windows with a horizontal central axis.
The advantages of using automatic ventilation systems
Modern systems of automatic ventilation of greenhouses have a number of advantages and are an indispensable attribute in a greenhouse. They are compact, have a high level of reliability, are equipped with an innovative installation system, are capable of being mounted on windows and doors and completely exempt the gardener from controlling climate change in the greenhouse. This saves time (especially in large greenhouses) and makes it possible to concentrate on solving other problems.
The standard warranty period for such devices is at least ten years. But with normal use, significantly exceeds this period. An important advantage of the system is the absence of its adjustment during the entire time of use and independence from power sources.
How to choose a thermal drive system for the greenhouse
In order to correctly select the necessary system of automatic airing thermal drive, It is necessary to pay attention to the type of window of your greenhouse and its size. On average, the area of the vents on the roof should be about 30% of the area of the roof itself. If the window closes under its own weight, then the simplest system will do, but if its design is with a vertical axis, then a more complex system or modification in the form of a spring is needed for the closing process.
Pay attention to the material from which the thermal drive is made. Although the system itself is located inside the greenhouse, the material must be anti-corrosion. This will prolong the life of the mechanism. An important factor is the force of opening. It should correspond to the type of your window frame and not exceed the maximum value specified in the instructions. Check the force of your window frame, you can use the balance. Manufacturers offer two types: up to 7 kg and up to 15 kg. Pay attention to the temperature range of opening. Usually it is 17-25 degrees. The maximum temperature of the system is standard 30 degrees.
Features of installation of the thermal drive in the greenhouse
Before installing the thermal drive in the greenhouse, you must make sure that the window opens easily, without much effort. Try on the thermal actuator to the place of attachment.At any position of the window its elements should not come into contact with the frame. The thermal actuator stem must be fully retracted before installation. To do this, keep the system in the refrigerator. According to the instructions, using a screwdriver, fix the brackets in the required places and install the system. Should remember that The system must be heated by the air of the greenhouse, and not by direct sunlight, so install a solar screen over the thermal drive.
