Wind power plants are classified according to two main features: the geometry of the wind wheel and its position relative to the direction of the wind.
Resistance to the incident wind flow is characterized by a parameter called geometric filling and equal to the ratio of the projection area of \u200b\u200bthe blades on a plane perpendicular to the flow to the area swept by them. So, for example, with identical blades, a four-blade wheel has twice as much geometric filling as a two-blade.
Wind turbines with a large geometric filling of the wind wheel develop significant power with a relatively weak wind, and maximum power is achieved at low wheel speeds.
Small-filled wind turbines reach maximum power at high speeds and go into this mode longer. Therefore, the first installations are used, for example, as water pumps, and even in weak winds they remain operational, and the second ones as electric generators where a high speed is required.
The main varieties of wind turbines are shown in Fig. fifteen.
They are divided into two groups:
Vane wind turbines with a horizontal axis of rotation (b ÷ d);
Wind turbines with a vertical axis of rotation (rotary: paddle (a) and orthogonal (e)).
Types of winged wind turbines differ only in the number of blades.
Vane wind turbines. For winged wind turbines, the greatest efficiency of which is achieved when the air flow is perpendicular to the plane of rotation of the wing blades, an automatic rotation axis rotation device is required. For this purpose, a stabilizer wing is used. Carousel wind turbines have the advantage that they can work in any direction of the wind without changing their position.
The coefficient of use of wind energy in winged wind turbines is significantly higher than that of rotary ones. At the same time, the carousel has a much larger torque. It is maximum for rotary blade aggregates at zero relative wind speed.
The distribution of winged wind turbines is explained by the value of their rotation speed. They can be directly connected to an electric current generator without a multiplier. The multiplier is a gearbox that increases the rotation speed of the generator shaft. The rotational speed of winged wind turbines is inversely proportional to the number of wings, therefore, units with more than three blades are practically not used.
Rotary wind turbines. The difference in aerodynamics gives roundabouts an advantage over traditional windmills. With increasing wind speed, they quickly increase traction, after which the rotation speed stabilizes. Carousel windmills are slow and this allows the use of simple electrical circuits, for example, with an asynchronous generator, without the risk of an accident in case of an accidental gust of wind. Slow-speed puts forward one limiting requirement - the use of a multi-pole generator operating at low speeds. Such generators are not widespread, and the use of multipliers is inefficient due to the low efficiency of the latter.
An even more important advantage of the carousel design was its ability to monitor “where the wind is blowing” without additional tricks, which is very important for surface yawing streams. The rotary vane wind turbine is the easiest to operate. Its design provides maximum torque when starting a wind turbine and automatic self-regulation of maximum rotation speed during operation. As the load increases, the rotation speed decreases and the torque increases until it stops completely.
Orthogonal wind turbines. Orthogonal wind turbines are the most promising for large energy. Today, when using orthogonal wind turbines, there are certain difficulties, one of which is the problem of their launch.
In orthogonal installations, the same wing profile is used as in a subsonic aircraft (see type e, Fig. 15). The plane, before "leaning" on the lifting force of the wing, must run up. The same is the case with the orthogonal installation. First, you need to bring energy to it - to unwind and bring it to certain aerodynamic parameters, and only then it will switch from engine mode to generator mode.
Many are interested in wind energy. The reasons for this interest are different: for someone, this is one of the few opportunities to provide electricity to the house; someone sees a windmill as a backup power source; others want complete independence from central power grids. Today there is such an opportunity - it is necessary to install a wind generator and not very sophisticated auxiliary equipment on the site. However, there are still some nuances that should be known in advance.
Kinetic wind energy can be converted into both electrical and mechanical or thermal energy. Thus, with the help of wind, it is possible not only to provide the house with electricity, but, for example, to raise water from the well, without intermediate transformation of the kinetic energy of the wind flow into electrical energy.
In this or that case, a wind power installation will be needed, including a wind engine equipped with an energy converter and a battery. Power converters can be electric generators, hydraulic pumps, compressors. For example, if a wind power plant will serve only for irrigation, then it makes no sense to first receive electricity, and then use it to power electric pumps. The extra link of energy transformation reduces the efficiency of the wind power installation. In economic practice, only two types of transducers are mainly used - electrical and mechanical (for pumping water). In the first case, we are talking about the accumulation of electrical energy, which is used by consumers; in the second, on wind pumps providing the necessary pressure in drip irrigation systems, sprinklers, domestic water supply systems.
Types of wind turbines
Any wind turbine has blades, which, while sailing, take on part of the kinetic energy of the wind flow. The shape of these blades and the design of the wind wheel can be different. There are three main types of wind turbines: vane (similar to a propeller), rotary (rotary) and drum. The most common winged working bodies of a wind wheel, the axis of rotation of which is located horizontally. Their share is at least 90% of the total number of wind turbines.
It is such "windmills" in large numbers that can be found in Europe, and especially in the Netherlands. Wind power projects of this country, which started in the middle of the last century, have already paid for themselves many times. Contrary to popular belief that a wind power plant is not capable of generating a sufficient amount of electricity adequate to the cost of its installation and maintenance, entire villages in the Netherlands are powered exclusively by “windmills”. One powerful wind power installation is able to provide in full electricity to several hundred (!) Cottages. The wind turbine of this installation is installed on a very solid and stable structure, which is based on a massive reinforced concrete slab buried by 15-20 meters. It, like the root of a tree, holds a high tower, inside of which there is a staircase that allows you to serve the wind turbine. No stretch marks are used.
Vane Wind Turbines consist of a wind wheel, head, orientation mechanism (tail) and tower (or mast - depending on size).
The wind wheel can be equipped with one to eight or more blades. Depending on their number, wind turbines are divided into high-speed (up to 4 blades), average speed (4 ... 8 blades) and low-speed (from 8 blades).
The head is designed so that it can rotate around the vertical axis of the tower. Its shape depends on the power and purpose of the wind turbine - in turn, the factors that determine the transmission system, its design and the number of stages.
The tail works on the principle of a weather vane and turns the head in the wind. Its surface area depends on the aerodynamic parameters of the wind wheel blades.
The tower raises the wind turbine above all obstacles that reduce the pressure flow of the wind, and also ensures the safety of the rotation of the blades. When the wind speed exceeds 35-45 m / s, the brake system is activated, completely stopping the wind turbine.
The number of blades of a winged wind wheel depends on the average wind speed in the area of \u200b\u200binstallation of the wind power installation. On open spaces, sea and oceanic coasts, small-winged winged wind motors are used, for the launch of which a minimum wind speed of 5-8 m / s is required. These are the most simple in design wind turbines with high efficiency, but creating a lot of noise.
In areas where the wind speed rarely exceeds 5 m / s, as a rule, it is recommended to install multi-blade wind turbines. They work almost silently, but also have lower efficiency than low-lobed; In addition, the manufacture of multi-blade wind turbines takes more materials, because during operation, a wind turbine of this type experiences increased gyroscopic loads.
Rotary wind turbines (they are carousel) also have a simple design, but have much lower efficiency - a maximum of 18%. The problem of their use also lies in the fact that they use rather rare multipolar electric generators. Rotary wind turbines have a vertical axis of rotation and blades, working like a sail. One of the advantages of this type of wind turbine is the lack of an orientation mechanism. The vertical axis of rotation allows the safe use of a rotary wind wheel at a low tower height. Such wind turbines start at low wind speeds and do not make noise. The main drawback of rotor wind turbines is the low wind utilization, since only part of the blades are constantly involved in the work; the rest either overcome the wind resistance or are isolated from it by an umbrella (casing).
Over the past decade, the market for wind energy installations (wind turbines) has significantly replenished primarily with compact models that could find application in estates and farms. They are designed for a small initial wind speed of 2.5 ... 3 m / s and the installation of a wind turbine at a height of 6 ... 17 m. The nominal amount of electricity is generated even at 6 ... 8 m / s (wind turbine rotation speed of 250 ... 300 r / m.).
Wind generators at work
The wind speed is not constant and therefore it is not possible to obtain “clean” electricity with stable parameters from the converter. The generator, as a rule, produces a voltage of 0 ... 56 V. The generated "dirty" energy is accumulated by the batteries that the wind turbine is equipped with, which ensures uninterrupted operation of the system. During strong winds, the unit operates at maximum power and stores energy for future use in order to give it up in calm or in low winds. Often, solar panels are used together with a wind turbine, which provide battery charge in the summer, when winds are especially weak.
To convert the direct current of batteries to alternating current with parameters 220V / 50 Hz, wind turbines are equipped with inverters.
In order to overcome peak loads, wind turbines are combined with auxiliary sources of electricity, such as diesel and gasoline generators, as well as (as an auxiliary) centralized power grid.
Individual low-power wind turbines are gradually becoming cheaper and more efficient. Along with this, the prospects for their application for private homes and farms are increasing. For example, for cottages in remote areas, it is important to have an autonomous wind power installation with a capacity of 20-50 kW, which guarantees the operation of the main electrical equipment in the absence of all other sources.
Wind pumps
People have learned to raise water from depth with the help of wind for a long time, however this method has not been forgotten today, especially where sources of electricity are inaccessible. The idea of \u200b\u200bthe invention is simple - to use wind energy to drive a water pump.
The most common wind pumps were in the United States. Once they decided the fate of the country's economy, and today they have also become a kind of religious building of the traditional setting of the American ranch.
In the post-Soviet space, wind pumps are a rarity, although during the garden and garden boom of the mid-80s, their popularity increased. Circumstances forced. Nowadays, the prerequisites are also emerging for turning to the already forgotten “Daisies” and “Aquarius”, since the share of electricity in the cost of vegetables is growing from year to year.
Wind turbine “Camomile” was developed by NPO “Vetroen”. His initial drawings were published in the magazine "Model Designer" in 1988, which outlined the manual for the independent manufacture of a wind pump.
Both units have the most simplified design. They are designed to absorb water from a depth of 8 m and work already at a wind speed of 3 m / s. The “Camomile” wind wheel has 12 blades and drives the pump diaphragm by means of a cam-lever mechanism with vertical traction passing inside the support of the wind turbine.
At a wind speed of 5 m / s, the Romashka wind pump raises an 8-meter depth to 300 liters of water per hour, and is capable of delivering it to a height of 10 meters. Paired with a drip irrigation system, this unit provides a real opportunity to cultivate garden crops in remote areas, if there is a reservoir or well up to 8 meters deep there.
The principle of operation of all wind motors is the same: under the pressure of the wind, the wind wheel rotates with the blades, transmitting torque through the transmission system to the shaft of the generator that generates electricity, to the water pump. The larger the diameter of the wind wheel, the greater the air flow it captures and the more energy the aggregat produces.
The traditional layout of windmills - with a horizontal axis of rotation (Fig. 3) Is a good solution for units of small sizes and capacities. When the span of the blades increased, this arrangement was ineffective, since at different heights the wind blows in different directions. In this case, not only is it not possible to optimally orient the unit in the wind, but there is a danger of destruction of the blades. In addition, the ends of the blades of a large installation, moving at high speed, create noise. However, the main obstacle to the use of wind energy is still an economic one - the power of the unit remains small and the share of the costs of its operation is significant. Low-power units can generate energy about three times more expensive.
Figure 3 - Vane wind turbine
Existing Wind Turbine Systems according to the scheme of the wind wheel device and its position in the wind stream are divided into three classes.
First grade includes wind turbines in which the wind wheel is located in a vertical plane; the plane of rotation is perpendicular to the direction of the wind, and, therefore, the axis of the wind wheel is parallel to the flow. Such wind turbines are called winged.
Speed \u200b\u200bis the ratio of the peripheral speed (ωR) of the end of the blade to the wind speed V:
|
Vane wind engines, according to GOST 2656-44, depending on the type of wind wheel and speed, are divided into three groups (Figure 4):
Ø multi-blade, low-speed wind engines with high speed Zn£ 2;
Ø low-speed, low-speed wind engines, including windmills, with high speed Zn> 2;
Ø low-speed, low-speed wind motors, Zn³3.
Figure 4 - Schemes of wind wheels of winged wind engines: 1 - multi-blade; 2–4 - small-lobed
To second grade include wind turbine systems with the vertical axis of rotation of the wind wheel . According to the constructive scheme, they are divided into groups:
- rotary, in which non-working blades are either covered by a screen, or are located with an edge against the wind (Figure 5, pos. 1);
- rotarysavonius wind turbines.
TO third grade include windmills operating on the principle of a water mill wheel and called drum (figure 5, item 7 ) . For these wind turbines, the axis of rotation is horizontal and perpendicular to the direction of the wind.
Figure 5 - Types of wind turbines: 1 - rotary; 2-3 multi-lobed; 4–5 - low-lobed; 6 - orthogonal; 7 - drum
The main disadvantages of rotary and drum wind turbines follow from the very principle of the location of the working surfaces of a wind wheel in a wind stream:
1. Since the rotor blades of the wheel move in the direction of air flow, the wind load does not act simultaneously on all the blades, but in turn. As a result, each blade experiences an intermittent load; the coefficient of utilization of wind energy is very low and does not exceed 10%.
2. The movement of the surfaces of the wind wheel in the direction of the wind does not allow to develop large revolutions, since the surfaces can not move faster than the wind.
3. The dimensions of the used part of the air flow (sweeping surface) are small in comparison with the dimensions of the wheel itself, which significantly increases its weight, referred to a unit of the installed power of the wind turbine.
Rotary wind turbines they have the advantage that they can work in any direction of the wind without changing their position.
The Savonius rotor wind turbines have the highest wind energy utilization of 18%.
Vane wind turbines are free from the above disadvantages of carousel and drum wind turbines. Good aerodynamic qualities of winged wind turbines, constructive ability to produce them at high power, relatively light weight per unit of power are the main advantages of wind turbines of this class
Commercial use of winged wind turbines began in 1980. Over the past 14 years, the power of wind turbines has increased 100 times: from 20 ... 60 kW with a rotor diameter of about 20 m at the beginning of the 1980s to 5000 kW with a rotor diameter of more than 100 m by 2003 (Fig. 7.6).
Types of winged wind turbines differ only in the number of blades.
For winged wind turbines, the greatest efficiency of which is achieved when the air flow is perpendicular to the plane of rotation of the wing blades, a device for automatically rotating the axis of rotation is required. For this purpose, a stabilizer wing is used.
The coefficient of utilization of wind energy (Fig. 4) for vane wind turbines is much higher than for rotary ones. At the same time, the carousel has a much larger torque. It is maximum for rotary blade aggregates at zero relative wind speed.
The distribution of winged wind turbines is explained by the value of their rotation speed. They can be directly connected to an electric current generator without a multiplier. The rotational speed of winged wind turbines is inversely proportional to the number of wings, therefore, units with more than three blades are practically not used.
The difference in aerodynamics gives carousel installations an advantage over traditional windmills (Figure 7). With an increase in wind speed, they quickly increase traction, after which the rotation speed stabilizes. Carousel windmills are slow and this allows the use of simple electrical circuits, for example, with an asynchronous generator, without the risk of an accident in case of an accidental gust of wind. Slow-moving puts forward one limiting requirement - the use of a multi-pole low-speed generator. Such generators are not widespread, and the use of multipliers (Multiplier [lat. Multiplicator multiplying] - increasing gear) is not effective due to the low efficiency of the latter.
An even more important advantage of the carousel design was its ability, without additional tricks, to monitor “from where the wind is blowing”, which is very important for surface yawing streams. Wind turbines of this type are being built in the USA, Japan, England, Germany, Canada.
The rotary vane wind turbine is the easiest to operate. Its design provides maximum torque when starting a wind turbine and automatic self-regulation of the maximum rotation speed during operation. With an increase in the load, the rotation speed decreases and the torque increases up to a complete stop.
When the flow interacts with the blade, the following occur:
1) the resistance force parallel to the relative velocity vector of the oncoming flow;
2) lifting force perpendicular to the force of resistance;
3) the turbulence of the streamlined flow lobe;
4) turbulization of the flow, i.e., chaotic perturbations of its velocity in magnitude and direction;
5) an obstacle to the flow.
The obstacle for the incoming flow is characterized by a parameter called geometric filling and equal to the ratio of the projection area of \u200b\u200bthe blades on a plane perpendicular to the flow to the area swept by them.
The main classification features of wind power plants can be determined by the following criteria:
1. If the axis of rotation of the wind wheel is parallel to the air flow, the installation will be horizontally axial, if the axis of rotation of the wind forest is perpendicular to the air flow - vertically axial.
2. Installations that use drag force as a rotational force (drag machines), as a rule, rotate with a linear speed less than wind speed, and installations using lift force (elevator machines) have a linear speed of the ends of the blades, significantly higher wind speed.
3. For most installations, the geometric filling of the wind wheel is determined by the number of blades. Wind turbines with a large geometric filling of the wind wheel develop significant power with a relatively weak wind, and maximum power is achieved with a small speed of the wheel. Small-filled wind turbines reach maximum power at high speeds and go into this mode longer. Therefore, the first installations are used, for example, as water pumps, and even with a weak wind they remain operational, and the second as electric generators where a high speed is required.
4. Installations for the direct performance of mechanical work are often called a windmill or a turbine, installations for the production of electricity, that is, a combination of a turbine and an electric generator, are called wind generators, air generators, and also plants with energy conversion.
5. For air generators connected directly to a powerful energy system, the rotational speed is constant due to the effect of asynchronization, but such installations use wind energy less efficiently than installations with a variable rotational speed.
6. The wind wheel can be connected directly to the electric generator (hard coupling) or through an intermediate energy converter that acts as a buffer. The presence of a buffer reduces the consequences of fluctuations in the rotational speed of the wind wheel, and allows more efficient use of wind energy and the power of the generator. In addition, there are partially decoupled schemes for connecting the wheel to the generator, called soft-coupled. Thus, a non-rigid connection, along with the inertia of the wind wheel, reduces the influence of fluctuations in wind speed on the output parameters of the generator. To reduce this effect also allows the elastic connection of the blades with the axis of the wind wheel, for example, using spring-loaded joints.
Wind wheel with a horizontal axis. Consider the horizontal-axial propeller-type wind wheels. The main rotational force of this type of wheel is lift. Regarding wind, the wind wheel in the working position can be located in front of or behind the support tower.
Wind turbines usually use two- and three-pasted wind turbines, the latter are characterized by a very smooth ride. The electric generator and gearbox connecting it to the wind wheel are usually located on top of the support tower in the rotary head.
Multi-vane wheels that develop high torque in light winds are used for pumping water and other purposes that do not require a high speed of the wind wheel.
Vertical axis wind generators (Figure 7). Wind-driven generators with a vertical axis of rotation due to their geometry in any direction of the wind are in the working position. In addition, this scheme allows, due to only lengthening the shaft, to install a gearbox with generators at the bottom of the tower.
The principal disadvantages of such installations are: the much greater susceptibility to their fatigue fractures due to more self-oscillating processes that often occur in them and torque pulsation, leading to undesirable pulsations of the output parameters of the generator. Because of this, the vast majority of wind generators are made according to the horizontal axis scheme, however, research on various types of vertical axis installations continues.
The most common types of vertical axis installations are as follows:
1. Cup rotor (anemometer). A wind wheel of this type rotates by the force of resistance. The shape of the bowl-shaped blade provides an almost linear dependence of the wheel speed on the wind speed.
2.Savonius rotor. This wheel also rotates with a drag force. Its blades are made of thin curved sheets of rectangular shape, i.e. they are simple and cheap. The rotating moment is created due to the different resistance exerted by the rotor blades concave and curved relative to it. Due to the large geometric filling, this wind wheel has a large torque and is used for pumping water.
3.Rotor Daria. The torque is created by the lifting force that occurs on two or three thin curved bearing surfaces having an aerodynamic profile. The lifting force is maximal at the moment when the blade crosses the incoming air flow at high speed. The Darier rotor is used in wind power generators. As a rule, a rotor cannot spin up independently, therefore a generator operating in engine mode is usually used to start it.
4.RotorMasgrove. The blades of this wind wheel in working condition are located vertically, but have the ability to rotate or fold around a horizontal axis when turned off. There are various options for Masgrove rotors, but they all turn off when the wind is strong.
5.Evans rotor. The blades of this rotor in emergency and during rotation are rotated around a vertical axis.
Figure 7 - Wind-driven generators with a vertical axis
Hubs The power of a wind power plant depends on the energy efficiency of the air flow. One of the ways to increase it is to use special air concentrators (amplifiers). For horizontal-axis wind generators, various versions of such concentrators have been developed. It can be diffusers or confusers (deflectors), directing air flow to the windwheel from an area larger than the swept area of \u200b\u200bthe rotor, and some other devices. Concentrators have not yet received wide distribution in industrial plants.
Existing wind turbine systems according to the scheme of the wind wheel device and its position in the wind stream are divided into three classes. In fig. 5.4 presents the basic design of the main types of rotors and wind turbines.
First grade includes wind turbines in which the wind wheel is located in a vertical plane; the plane of rotation is perpendicular to the direction of the wind, and, therefore, the axis of the wind wheel is parallel to the flow. Such wind turbines are called vane.
The ratio of the peripheral speed of the end of the blade to the wind speed: called speed
Vane wind engines, according to GOST 2656-44, depending on the type of wind wheel and speed, are divided into three groups:
· Multi-blade, low-speed wind engines with high speed Zn ≤ 2.
· Low-vane, low-speed wind engines, including windmills, with a speed of Zn\u003e 2.
· Low-vane, high-speed wind motors, Zn ≥ 3.
To second grade include wind turbine systems with a vertical axis of rotation of the wind wheel. According to the constructive scheme, they are divided into groups:
· Carousel, in which non-working blades are either covered by a screen, or are located with an edge against the wind;
· Rotary wind turbines of the Savonius system.
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a device that converts wind energy into rotational energy. The main working body of the wind turbine is a rotating unit - a wheel driven by the wind and rigidly connected to the shaft, the rotation of which drives the equipment that performs useful work. The shaft is mounted horizontally or vertically. Wind turbines are usually used to generate energy consumed periodically: when pumping water in a tank, grinding grain, in temporary, emergency and local power networks. History reference. Although surface winds do not always blow, they change their direction and their strength is unstable, a wind turbine is one of the oldest machines for generating energy from natural sources. Due to the dubious reliability of ancient written reports about wind turbines, it is not clear when and where such machines first appeared. But, judging by some records, they existed already before the 7th century. AD It is known that in Persia they were used in the 10th century, and in Western Europe the first devices of this type appeared at the end of the 12th century. During the 16th century the tent-type Dutch windmill was finally formed. No significant changes in their design were observed until the beginning of the 20th century, when, as a result of research, the shapes and coatings of the wings of mills were significantly improved. Since low-speed cars are bulky, in the second half of the 20th century. began to build high-speed wind turbines, i.e. those whose wind wheels can make a large number of revolutions per minute with a high coefficient of utilization of wind energy. Modern types of wind turbines. Currently, three main types of wind motors are used - drum, vane (screw type) and rotary (with S-shaped profile of the repeller). Drum and winged. Although the drum-type wind wheel has the lowest coefficient of use of wind energy in comparison with other modern repellers, it is used most widely. On many farms, water is pumped with it, if for some reason there is no mains electricity. A typical shape of such a wheel with sheet metal blades is shown in Fig. 1. Drum and wing type wind wheels rotate on a horizontal shaft, so they need to be turned in the wind to get the best performance. To do this, they are given a rudder - a blade located in a vertical plane, which ensures the rotation of the wind wheel to the wind. The wheel diameter of the world's largest wing-type wind turbine is 53 m, the maximum width of its blade is 4.9 m. The wind wheel is directly connected to an electric generator with a capacity of 1000 kW, which develops at a wind speed of at least 48 km / h. Its blades are regulated in such a way that the rotational speed of the wind wheel remains constant and equal to 30 rpm in the range of wind speeds from 24 to 112 km / h. Due to the fact that in the area where such wind turbines are located, winds blow quite often, a wind power plant usually generates 50% of maximum power and feeds the public electricity grid. Winged wind motors are widely used in remote rural areas to provide electricity to farms, including for charging batteries of radio communication systems. They are also used in aircraft power plants and guided missiles. S-shaped rotor. The S-shaped rotor mounted on a vertical shaft (Fig. 2) is good in that a wind turbine with such a repeller does not need to be taken into the wind. Although the torque on its shaft varies from a minimum to one third of the maximum value per half revolution, it does not depend on the direction of the wind. When a smooth circular cylinder rotates under the influence of wind, a force perpendicular to the direction of the wind acts on the cylinder body. This phenomenon is called the Magnus effect, in honor of the German physicist who studied it (1852). In 1920-1930, A. Flettner used rotating cylinders (Flettner rotors) and S-shaped rotors to replace vane wind wheels, as well as movers of a ship that made the transition from Europe to America and vice versa. The utilization of wind energy. The power received from the wind is usually small - less than 4 kW develops an outdated type of Dutch windmill at a wind speed of 32 km / h. The wind flow power that can be used is generated from the kinetic energy of the air masses, carried per unit time perpendicular to the area of \u200b\u200ba given size. In a wind turbine, this area is determined by the windward surface of the repeller. When taking into account the height above sea level, the air pressure on it and its temperature, the available power N (in kW) per unit area is determined by the equation N \u003d 0.0000446 V3 (m / s). The coefficient of utilization of wind energy is usually defined as the ratio of the power developed on the shaft of the wind turbine to the available power of the wind flow acting on the windward surface of the wind wheel. This coefficient becomes maximum at a certain ratio between the speed of the outer edge of the blade of the wind wheel w and the wind speed u; the value of this w / u ratio depends on the type of wind turbine. The coefficient of use of wind energy depends on the type of wind wheel and ranges from 5-10% (Dutch mill with flat wings, w / u \u003d 2.5) to 35-40% (profiled winged repeller, 5? W / u? 10).