Types of wind turbines. Types of wind turbines What is the maximum efficiency of drum wind turbines

Wind turbines use the power and strength of the wind to generate electricity. Modern human life is unthinkable without

electricity, even in areas remote from the electricity supply. Wind power producers of clean light energy serve as an alternative source.

And they are becoming more and more popular every year. The larger the assortment of goods, the more questions arise as to which type of wind generator to prefer. And in terms of productivity and money.

The main types of wind turbines

Models of wind generators are of different designs, differ in power. According to the geometry of rotation of the axis of the main rotor, they are divided into:

1. Vertical type - the turbine is located vertically relative to the ground plane. Starts working in light wind.
2. Horizontal type - the rotor axis rotates parallel to the earth's surface. Has a large power of converting wind energy into alternating and direct current.

Let us examine these types in more detail, since each of them has developments and improvements.

Varieties of vertical generators (carousel type)

Vertical converters of wind power into energy are often used for domestic needs. These types of wind turbines are easy to maintain. The main components that require attention are located at the bottom of the units and are free to access.

1. Generators with Savounis rotor

Consist of two cylinders. Constant axial rotation and wind flow are not dependent on each other. Even with sharp gusts, it spins at the initially set speed.

The lack of influence of the wind on the rotation speed is undoubtedly its good advantage. The bad thing is that he uses the power of the elements not for all of its power, but only for a third. The arrangement of the blades in the form of half-cylinders allows working only in a quarter of a turn.

2. Generators with Darrieus rotor

They have two or three blades. Easy to assemble. The design is simple and straightforward. Start to work from manual launch.

Minus - turbines are not powerful work. Strong vibration causes high noise. This is facilitated by the large number of blades.

3. Helical rotor

The wind generator rotates evenly due to the swirling blades. The bearings are not subject to rapid wear, which significantly extends the service life.

Installation of the unit is time-consuming and difficult to assemble. The sophisticated manufacturing technology resulted in the high price.

4. Multi-blade rotor

The vertical-axial design with a large number of blades makes it sensitive even to very light winds. The efficiency of such wind generators is very high.

It is a powerful converter. Wind energy is used to the maximum. It is expensive. The disadvantage is a high sound background. Can produce a large amount of electric current.

5. Orthogonal rotor

Starts generating energy at a wind speed of 0.7 m / s. Consists of a vertical axis and blades. It does not make much noise, it has a beautiful unusual design. Service life is several years.

Heavy blades make it bulky, which complicates installation work.

Positive aspects of vertical wind turbines:

1. The use of generators is possible even in light winds.
2. They are not tuned to wind currents, since they do not depend on its direction.
3. They are installed on a short mast, which allows maintenance of systems on the ground.
4. Noise within 30 dB.
5. Diverse, pleasant appearance.

The main flaw is that the force and energy of the wind is not fully used due to the low rotational speed of the rotor.

Horizontal wind turbines (vane)

Various modifications of horizontal installations have from one to three blades or more. Therefore, the efficiency is much higher than that of vertical ones.

The disadvantages of wind generators are the need to orient them to the direction of the wind. Continuous movement will reduce the rotation speed, which will reduce its performance.

1. Single-bladed and double-bladed. They are distinguished by high motor speeds. The weight and dimensions of the unit are small, which makes installation easier.
2. Three-bladed. They are in demand in the market. They can generate energy up to 7 mW.
3. Multi-blade machines have up to 50 blades. They are characterized by great inertia. The advantages of torque are used in the operation of water pumps.

Wind turbines with different designs from classical designs appear on the modern market, for example, there are hybrid ones.

1. Wind turbine, arranged like a sailboat

The poppet-like structure under the pressure of air drives the pistons, which activate the hydraulic system. As a result, there is a transformation of physical energy into electrical energy.

The unit does not make noise during operation. High power ratings. Easy to manage.

2. Flying wind turbine-wing

Used without mast, generator, rotor and blades. In comparison with classical structures, which function at low heights with variable wind force, and the construction of high masts is laborious and expensive, the “wing” does not have such problems.

It is launched to a height of 550 meters. Electricity generation is 1 MW per year. The wing is manufactured by Makani Power.

Application of wind turbines

Wind turbines are used in industry and in everyday life.

Industrial wind turbines are used for the needs of production or providing electricity to small villages in the absence or shortage of electricity. They are installed in open desert areas in large numbers.

Windmills, mostly simple, are intended for home use in summer cottages. In the cold winter season, to save electricity, they are built on the territory of residential buildings. A simple wind turbine provides energy according to the number of windy days.

Wind turbine efficiency

For vertical and horizontal wind turbines, the efficiency is approximately the same. For vertical it is 20-30%, for horizontal 25-35%.

Efficiency depends on the type of wind generator and wind speed

Some manufacturers increase the efficiency of vertical wind turbines up to 15% by replacing bearings with permanent neodymium magnets. But such a slight increase in efficiency by only 3-5% leads to a significant increase in the cost of structures.

Both types do not differ in terms of service life. On average, the duration of energy production is calculated for 15 - 25 years of service. The support-bearing assembly and blades wear out the fastest. The service life of which depends on the quality of service.

Wind turbine cost

Wind turbine prices are quite high. These are bulky structures that are made from expensive materials. Includes batteries, controller, inverter and mast.

The kit can consist of: 1 - the wind generator itself, 2 - Mast, 3 - Foundation, 4 - Battery set, 5 - Inverter, 6 - Controller, as well as wires, connectors, rack, diesel generator and other consumables required for installation

The technical characteristics of wind turbines also affect the cost.

1. The simplest is a generator with low power up to 300 watts. Produces energy with a wind force of 10-12 m / s. A set of the simplest wind turbine with only a controller costs 15,000 rubles. In a complete set with an inverter, a battery and a mast, the price reaches 50,000 rubles.
2. Generators with a declared power of 1 kW. With a weak wind, on average, they produce energy from 30-100 kW per month. For a large house with high energy consumption, it is recommended to use diesel and gasoline units in addition. They will also recharge the batteries during calm days. Such a wind generator costs from 150,000 rubles. It also comes to 300-400 thousand rubles with a more complete set.
3. Electrical consumption in a large house with a backyard will require a 3-5 kW wind turbine. Enough batteries, more powerful inverter, controller, high mast. One set costs from 300,000 rubles to a million.

If the house was also heated by the wind, then the installation should be chosen with a capacity of 10 kW. And take care of additional sources such as solar panels. You may also need a gas generator. It all depends on how much energy you have to keep in reserve in case of calm and cloudy days.

Wind turbine manufacturers

In connection with the growing demand for an environmentally friendly method of generating electricity, offers from leading manufacturers of wind turbines appear on the market. You can always find the best option.

• Denmark "Vestas" with a market share of 12.7%
• China "Snovel" - 9, 0%
• China "Goldwind" - 8.7%
• Spain "Gamesa" - 8.0%
• Germany "Enercon" - 7.8%
• India "Suzlon" - 7.6%
• China "Guodian United Power" - 7.4%
• Germany "Siemens" - 6.3%
• China "Ming Yang" - 3.6%

The production of wind generators was also set up by domestic manufacturers: in the Moscow region - Vetro Svet LLC, SKB Iskra LLC, Sapsan-Energiya LLC, Agregat-Privod CJSC, in St. Petersburg - Wind Energy Company CJSC.

Selection rule

Choosing a wind generator is not difficult if you approach it responsibly. Better in advance.

1. Calculate the amount of energy needed to power your home.
2. Find out the average annual wind speed, take into account at what time the windmill will be inactive, and at what time it is possible to provide sufficient volume. Power must be taken with a margin. Calculate the number of batteries to store energy in case of calm.
3. Take into account the climatic features of the place of residence. In the central zone of Russia, there are severe frosts for most of the winter. Installation of wind turbines does not justify itself there.
4. Rain and snow will reduce energy production. These are the cons.
5. Pay attention to the number of blades. The fewer there are, the more efficiency.
6. Find out the intensity of the noise during the operation of the installation.
7. Compare the parameters of wind turbines. Carefully familiarize yourself with their technical and comparative characteristics.
8. Feedback from people who already use the systems will help to select a wind generator.
9. Review manufacturers when choosing a generator.

Wind and sun are natural, environmentally friendly and waste-free energy sources. In an age when the potential of natural resources is depleted, the production of wind turbines is gaining speed.

Wind map of Russia for the selection of a wind generator

Windmills are becoming more and more popular among ordinary people. All conditions have been created for this. A variety of wind turbines and the availability of thematic information to help you choose.

Russia has a twofold position with regard to wind energy resources. On the one hand, due to the huge total area and the abundance of flat areas, there is generally a lot of wind, and it is mostly flat. On the other hand, our winds are mostly low-grade, slow, see fig. On the third, the winds are violent in sparsely populated areas. Based on this, the task of starting a wind generator on the farm is quite relevant. But in order to decide whether to buy a rather expensive device, or to make it yourself, you need to think carefully about which type (and there are a lot of them) for which purpose to choose.

Basic concepts

1. KIEV - coefficient of use of wind energy. If used for calculating a mechanistic model of a plane wind (see below), it is equal to the efficiency of the rotor of a wind power plant (APU).
2. Efficiency is the through efficiency of the APU, from the oncoming wind to the terminals of the electric generator, or to the amount of water pumped into the tank.
3. The minimum operating wind speed (MWS) is its speed at which the wind turbine begins to supply current to the load.
4. The maximum permissible wind speed (MDS) is its speed at which the generation of energy stops: the automation either turns off the generator, or puts the rotor in a weather vane, or folds it and hides it, or the rotor itself stops, or the APU simply collapses.
5. Starting wind speed (SWS) - at this speed, the rotor can turn without load, spin up and enter the operating mode, after which you can turn on the generator.
6. Negative starting speed (OSS) - this means that the APU (or wind turbine - wind power plant, or VEA, wind power unit) to start at any wind speed requires a mandatory spin-up from an external energy source.
7. Starting (initial) torque - the ability of a rotor, forcibly braked in the air flow, to create a torque on the shaft.
8. A wind turbine (VD) is a part of the APU from the rotor to the shaft of a generator or pump, or other energy consumer.
9. Rotary wind generator - APU, in which wind energy is converted into torque on the power take-off shaft by rotating the rotor in the air stream.
10. Rotor operating speed range is the difference between MDS and MPC when operating at rated load.
11. Slow-speed windmill - in it the linear speed of the rotor parts in the stream does not significantly exceed the wind speed or below it. The dynamic flow head is directly converted to blade thrust.
12. High-speed wind turbine - the linear speed of the blades is significantly (up to 20 or more times) higher than the wind speed, and the rotor forms its own air circulation. The cycle of converting flow energy into thrust is complex.

Notes:

1. Low-speed APUs, as a rule, have KIEV lower than high-speed ones, but have a starting torque sufficient to spin up the generator without disconnecting the load and zero TCO, i.e. absolutely self-starting and applicable in the lightest winds.
2. Slowness and speed are relative concepts. A household wind turbine with 300 rpm can be low-speed, and powerful APUs of the EuroWind type, from which the fields of wind power plants, wind farms (see Fig.) And whose rotors make about 10 rpm, are high-speed, because with such their diameter, the linear velocity of the blades and their aerodynamics over the greater part of their span are quite “airplane-like,” see below.

What kind of generator do you need?

An electric generator for a household wind turbine must generate electricity in a wide range of rotation speeds and have the ability to self-start without automation and external power sources. In the case of using an APU with an OSS (wind turbines with spinning), which, as a rule, have high KIEV and efficiency, it must also be reversible, i.e. be able to work as an engine. At powers up to 5 kW, this condition is met by electric machines with permanent magnets based on niobium (super magnets); on steel or ferrite magnets, you can count on no more than 0.5-0.7 kW.

Note: asynchronous alternators or collector generators with a non-magnetized stator are not suitable at all. When the wind force decreases, they "go out" long before its speed drops to the MPC, and then they themselves will not start.

An excellent "heart" of the APU with a capacity of 0.3 to 1-2 kW is obtained from an alternator with a built-in rectifier; these are now the majority. Firstly, they keep the output voltage 11.6-14.7 V in a fairly wide range of speeds without external electronic stabilizers. Second, the silicon gates open when the voltage across the winding reaches approximately 1.4 V, and before that the generator “does not see” the load. To do this, the generator needs to be spinned up pretty well.

In most cases, the autogenerator can be directly, without a gear or belt drive, connected to the high-speed HP shaft, by selecting the speed by choosing the number of blades, see below. "Fast-walkers" have a small or zero starting torque, but the rotor will have enough time to spin up enough without disconnecting the load before the valves open and the generator will give current.

Choosing by the wind

Before deciding which wind generator to make, let's decide on the local aerology. In gray-greenish (windless) areas of the wind map at least some sense will only be from a sailing wind turbine (and we'll talk about them further). If you need a constant power supply, you will have to add a booster (a rectifier with a voltage stabilizer), a charger, a powerful battery, an inverter 12/24/36/48 V DC to 220/380 V 50 Hz AC. Such an economy will cost no less than $ 20,000, and it is unlikely that it will be possible to remove a long-term power of more than 3-4 kW. In general, with an unyielding desire for alternative energy, it is better to look for another source of it.

In yellow-green, weakly windy places, with a need for electricity up to 2-3 kW, you can take on a slow-speed vertical wind generator yourself... They have been developed innumerable, and there are designs that in terms of KIEV and efficiency are almost not inferior to industrial "blades".

If a wind turbine for a home is supposed to be bought, then it is better to focus on a wind turbine with a sail rotor. There are a lot of disputes, and in theory everything is still not clear, but they work. In the Russian Federation "sailboats" are produced in Taganrog with a capacity of 1-100 kW.

In red, windy regions, the choice depends on the required power. In the range of 0.5-1.5 kW, self-made "verticals" are justified; 1.5-5 kW - purchased sailboats. "Vertical" can also be purchased, but it will cost more than a horizontal APU. And, finally, if a wind turbine with a capacity of 5 kW or more is required, then you need to choose between horizontal purchased "blades" or "sailboats".

Note: many manufacturers, especially of the second tier, offer kits of parts from which you can assemble a wind generator with a capacity of up to 10 kW yourself. Such a set will cost 20-50% cheaper than a ready-made one with installation. But before buying, you need to carefully study the aerology of the proposed installation site, and then, according to the specifications, select the appropriate type and model.

About safety

Parts of a household wind turbine in operation can have a linear speed exceeding 120 or even 150 m / s, and a piece of any solid material weighing 20 g, flying at a speed of 100 m / s, with a "successful" hit, kills a healthy man on the spot. A steel, or hard plastic, plate 2 mm thick, moving at a speed of 20 m / s, cuts it in half.

In addition, most wind turbines over 100 W are quite noisy. Many generate ultra-low (less than 16 Hz) air pressure fluctuations - infrasounds. Infrasounds are inaudible, but destructive to health, and spread very far.

Note: in the late 1980s, there was a scandal in the United States - the largest wind farm in the country at that time had to be closed. The Indians from the reservation 200 km from the field of its APU proved in court that the health disorders that had sharply increased in them after the WPP was put into operation were due to its infrasound.

For the above reasons, the installation of the APU is allowed at a distance of at least 5 of their heights from the nearest residential buildings. In the courtyards of private households, industrial-made wind turbines can be installed, appropriately certified. It is generally impossible to install an APU on the roofs - during their operation, even with low-power ones, alternating mechanical loads arise that can cause a resonance of the building structure and its destruction.

Note: the height of the APU is the highest point of the swept disk (for blade rotors) or geomeric figure (for vertical APU with a rotor on the shaft). If the APU mast or the rotor axis protrude upward even higher, the height is calculated from their top - the top.

Wind, aerodynamics, KIEV

A home-made wind generator obeys the same laws of nature as a factory one, calculated on a computer. And a home-builder needs to understand the basics of his work very well - most often he does not have at his disposal expensive super-modern materials and technological equipment. The aerodynamics of the APU, oh, how difficult it is ...

Wind and KIEV

To calculate serial factory APU, the so-called. flat mechanistic wind model. It is based on the following assumptions:

• Wind speed and direction are constant within the effective rotor surface.
• Air is a continuous medium.
• The effective rotor surface is equal to the swept area.
• The energy of the air flow is purely kinetic.

Under such conditions, the maximum energy per unit volume of air is calculated by the school formula, assuming the air density under normal conditions is 1.29 kg * cubic meters. m. At a wind speed of 10 m / s, one cube of air carries 65 J, and 650 watts can be removed from one square of the effective surface of the rotor, at 100% efficiency of the entire APU. This is a very simplistic approach - everyone knows that the wind is never perfectly flat. But this has to be done to ensure the repeatability of products - a common practice in technology.

The flat model should not be ignored; it provides a clear minimum of available wind power. But the air, firstly, is compressed, and secondly, it is very fluid (dynamic viscosity is only 17.2 μPa * s). This means that the flow can flow around the swept area, reducing the effective surface and KIEV, which is most often observed. But in principle, the opposite situation is also possible: the wind flows to the rotor and the effective surface area will then be greater than the swept surface, and the KIEV will be greater than 1 relative to the same for a flat wind.

Here are two examples. The first is a pleasure yacht, rather heavy, the yacht can go not only against the wind, but also faster than it. Wind is meant outside; the apparent wind must still be faster, otherwise how will it pull the ship?

The second is a classic of aviation history. During the tests of the MIG-19, it turned out that the interceptor, which was a ton heavier than the front-line fighter, accelerated faster in speed. With the same engines in the same glider.

Theorists did not know what to think, and seriously doubted the law of conservation of energy. In the end, it turned out that it was the radar fairing cone protruding from the air intake. From its nose to the shell, an air seal appeared, as if raking it from the sides to the engine compressors. Since then, shockwaves have become firmly established in theory as useful, and the fantastic flight performance of modern aircraft is in no small part due to their skillful use.

Aerodynamics

The development of aerodynamics is usually divided into two eras - before N. G. Zhukovsky and after. His report "On the attached vortices" of November 15, 1905 marked the beginning of a new era in aviation.

Before Zhukovsky, they flew on sails set flat: it was assumed that the particles of the incoming stream give all their momentum to the leading edge of the wing. This made it possible to immediately get rid of the vector quantity - the angular momentum - which gave rise to furious and most often non-analytical mathematics, to move to much more convenient scalar purely energy relations, and as a result, the calculated pressure field on the bearing plane, more or less similar to the present.

Such a mechanistic approach made it possible to create vehicles that, at the very least, can take off and fly from one place to another, not necessarily crashing to the ground somewhere along the way. But the desire to increase speed, carrying capacity and other flying qualities more and more revealed the imperfection of the original aerodynamic theory.

Zhukovsky's idea was this: along the upper and lower surfaces of the wing, the air travels a different path. From the condition of the continuity of the medium (vacuum bubbles are not formed in the air by themselves), it follows that the velocities of the upper and lower flows descending from the trailing edge should be different. Due to the small but finite viscosity of the air, a vortex should form there due to the difference in velocities.

The vortex rotates, and the law of conservation of momentum, which is as immutable as the law of conservation of energy, is also valid for vector quantities, i.e. must take into account the direction of movement. Therefore, right there, on the trailing edge, an oppositely rotating vortex with the same torque should be formed. By what means? Due to the energy generated by the engine.

For the practice of aviation, this meant a revolution: by choosing the appropriate wing profile, it was possible to send the attached vortex around the wing in the form of a circulation G, increasing its lift. That is, having spent a part, and for high speeds and wing loads - a large part, the engine power, it is possible to create an air flow around the apparatus, which allows achieving the best flight qualities.

This made aviation an aviation, and not part of aeronautics: now the aircraft could create itself the environment necessary for flight and no longer be a toy of air currents. All you need is a more powerful engine, and more and more powerful ...

KIEV again

But the windmill has no motor. On the contrary, it must take energy from the wind and give it to consumers. And here it comes out - he pulled out his legs, the tail got stuck. Too little wind energy was allowed on the rotor's own circulation - it will be weak, the thrust of the blades will be low, and the KIEV and power will be low. Let's give a lot for circulation - the rotor will spin like mad at idle in a weak wind, but consumers again get little: they gave a little load, the rotor braked, the wind blew off the circulation, and the rotor became.

The law of conservation of energy gives the "golden mean" just in the middle: we give 50% of the energy to the load, and for the remaining 50% we twist the flow to the optimum. Practice confirms the assumptions: if the efficiency of a good pulling propeller is 75-80%, then the KIEV, just as carefully calculated and blown in a wind tunnel of the blade rotor, reaches 38-40%, i.e. up to half of what can be achieved with an excess of energy.

Modernity

Today, aerodynamics, armed with modern mathematics and computers, is increasingly moving away from inevitably something and simplifying models to an accurate description of the behavior of a real body in a real flow. And here, in addition to the general line - power, power, and more power! - side paths are found, but promising just with a limited amount of energy entering the system.

The famous alternative aviator Paul McCready created an airplane back in the 80s, with two motors from a chainsaw with a power of 16 hp. showing 360 km / h. Moreover, its chassis was non-retractable tricycle, and the wheels were without fairings. None of McCready's vehicles went online and went on alert, but two - one with piston motors and propellers, and the other jet - flew around the globe for the first time in history without landing at one gas station.

The development of the theory also affected the sails that gave rise to the original wing very significantly. "Live" aerodynamics allowed the yachts in 8 knots wind. stand on hydrofoils (see fig.); to accelerate such a whopper to the required speed with a propeller, an engine of at least 100 hp is required. Racing catamarans sail at about 30 knots in the same wind. (55 km / h).

There are also completely non-trivial finds. Fans of the rarest and most extreme sport - base jumping - wearing an apecial wing suit, wingsuit, fly without a motor, maneuvering, at a speed of more than 200 km / h (picture on the right), and then smoothly land in a pre-selected place. In what fairy tale do people fly by themselves?

Many mysteries of nature have also been resolved; in particular - the flight of a beetle. According to classical aerodynamics, it cannot fly. In the same way as the founder of the "stealth" F-117 with its diamond-shaped wing, is also unable to take off. And the MiG-29 and Su-27, which for some time can fly with their tail forward, do not fit into any ideas at all.

And why, then, dealing with wind turbines, not fun and not a tool for destroying their own kind, but a source of a vital resource, is it necessary to dance without fail from the theory of weak streams with its flat wind model? Isn't there a way to go further?

What to expect from a classic?

However, in no case should you give up the classics. It provides a foundation without leaning on which one cannot rise higher. In the same way, as set theory does not cancel the multiplication table, and quantum chromodynamics does not leave apples from trees upwards.

So what can you expect with the classic approach? Let's look at the picture. Left - types of rotors; they are shown conditionally. 1 - vertical carousel, 2 - vertical orthogonal (wind turbine); 2-5 - bladed rotors with different number of blades with optimized profiles.

On the right, along the horizontal axis, the relative rotor speed is plotted, i.e., the ratio of the linear speed of the blade to the wind speed. Vertical upwards - KIEV. And down - again, the relative torque. A single (100%) torque is considered to be one that creates a rotor forcibly braked in the flow with 100% KIEV, i.e. when all the energy of the flow is converted into a rotating force.

This approach allows for far-reaching conclusions. For example, the number of blades must be chosen not only and not so much according to the desired rotation speed: 3- and 4-blades immediately lose a lot in terms of KIEV and torque compared to 2- and 6-blades that work well in approximately the same speed range. And outwardly similar carousel and orthogonal have fundamentally different properties.

On the whole, preference should be given to blade rotors, except for cases when the utmost cheapness, simplicity, maintenance-free self-starting without automation are required and lifting to the mast is impossible.

Note: let's talk about sailing rotors especially - they, it seems, do not fit into the classics.

Vertical

APUs with a vertical axis of rotation have an indisputable advantage for everyday life: their units requiring maintenance are concentrated at the bottom and there is no need to lift them up. There remains, and even then not always, a self-aligning thrust bearing, but it is strong and durable. Therefore, when designing a simple wind turbine, the selection of options should be started with vertical units. Their main types are shown in Fig.

Sun

In the first position - the simplest one, most often called the Savonius rotor. In fact, it was invented in 1924 in the USSR by Ya. A. and A. A. Voronin, and the Finnish industrialist Sigurd Savonius shamelessly appropriated the invention, ignoring the Soviet copyright certificate, and began serial production. But the introduction in the fate of the invention means a lot, therefore, in order not to stir up the past and not disturb the ashes of the dead, we will call this wind turbine the Voronin-Savonius rotor, or, for short, VS.

The aircraft is good for everyone, except for the "locomotive" KIEV in 10-18%. However, in the USSR they worked on it a lot, and there are some developments. Below we will consider an improved design, which is not much more complicated, but according to KIEV gives a head start to the blades.

Note: the two-bladed aircraft does not spin, but jerks; The 4-blade is only slightly smoother, but loses a lot in KIEV. To improve the 4 - "trough" ones are most often carried over two floors - a pair of blades at the bottom, and another pair, rotated 90 degrees horizontally, above them. The KIEV remains, and the lateral loads on the mechanics are weakened, but the bending loads slightly increase, and with a wind of more than 25 m / s, such an APU on the shaft, i.e. without the bearing over the rotor stretched by the shrouds, "tears down the tower".

Daria

The next is the Darrieus rotor; KIEV - up to 20%. It is even simpler: the blades are made of a simple elastic band without any profile. The Darrieus rotor theory is not yet sufficiently developed. It is only clear that it begins to unwind due to the difference in the aerodynamic resistance of the hump and the pocket of the tape, and then it becomes kind of fast, forming its own circulation.

The torque is small, and in the starting positions of the rotor there is no parallel or perpendicular to the wind at all, so self-spinning is possible only with an odd number of blades (wings?). In any case, the load from the generator must be disconnected during spin-up.

The Darrieus rotor has two more bad qualities. First, during rotation, the thrust vector of the blade describes a full revolution relative to its aerodynamic focus, and not smoothly, but in jerks. Therefore, the Darrieus rotor quickly breaks its mechanics even in an even wind.

Secondly, Daria is not just making noise, but screaming and screaming, to the point that the tape breaks. This is due to its vibration. And the more blades, the stronger the roar. So, if Daria is made, then it is two-bladed, made of expensive high-strength sound-absorbing materials (carbon fiber, mylar), and a small aircraft is adapted for spinning in the middle of the mast-pole.

Orthogonal

On pos. 3 - orthogonal vertical rotor with profiled blades. Orthogonal because the wings stick out vertically. The transition from the VS to the orthogonal is illustrated in Fig. left.

The angle of installation of the blades relative to the tangent to the circle touching the aerodynamic foci of the wings can be either positive (in the figure) or negative, in accordance with the wind force. Sometimes the blades are made swiveling and weather vans are placed on them, automatically holding the "alpha", but such structures often break.

The central body (blue in the figure) allows you to bring the KIEV to almost 50 %.In a three-bladed orthogonal, it should have the shape of a triangle in section with slightly convex sides and rounded corners, and with a larger number of blades, a simple cylinder is sufficient. But the theory for the orthogonal gives the optimal number of blades unambiguously: there should be exactly 3 of them.

Orthogonal refers to high-speed wind turbines with OSS, i.e. necessarily requires promotion during commissioning and after calm. Serial unattended APUs with a capacity of up to 20 kW are produced according to the orthogonal scheme.

Helicoid

Helicoid rotor, or Gorlov's rotor (pos. 4) - a kind of orthogonal, providing uniform rotation; the orthogonal with straight wings “tears” only slightly weaker than the two-bladed BC. The bending of the blades along the helicoid allows you to avoid losses of KIEV due to their curvature. Although the curved blade rejects part of the flow without using it, it rakes part of it into the zone of the highest linear velocity, compensating for the losses. Helicoids are used less often than other wind turbines, because due to the complexity of their manufacture, they are more expensive than their counterparts of equal quality.

Barrel-zagrebka

5 pos. - BC type rotor surrounded by a guide vanes; its diagram is shown in Fig. on right. It is rarely found in industrial design, because expensive land acquisition does not compensate for the increase in capacity, and the consumption of materials and the complexity of production are great. But a self-builder who is afraid of work is no longer a master, but a consumer, and if no more than 0.5-1.5 kW is needed, then a tidbit for him:

• A rotor of this type is absolutely safe, silent, does not create vibrations and can be installed anywhere, even on a playground.
• Bending galvanized troughs and weld a frame from pipes is a nonsense job.
• The rotation is absolutely uniform, the mechanical parts can be taken from the cheapest or from the trash.
• Not afraid of hurricanes - too strong wind cannot push into the "barrel"; a streamlined vortex cocoon appears around it (we will encounter this effect later).
• And most importantly, since the surface of the "grab" is several times larger than that of the rotor inside, the KIEV can be over-unit, and the torque already at 3 m / s at the "barrel" of three-meter diameter is such that a 1 kW generator with a maximum load is it is said that it is better not to twitch.

Video: Lenz wind turbine

In the 60s in the USSR E.S.Biryukov patented a carousel APU with 46% KIEV. A little later, V. Blinov achieved 58% of the design based on the same principle of KIEV, but there is no data on its tests. And full-scale tests of the Armed Forces of Biryukov were carried out by the staff of the Inventor and Rationalizer magazine. A two-story rotor with a diameter of 0.75 m and a height of 2 m in a fresh wind spun an asynchronous generator of 1.2 kW at full power and withstood 30 m / s without breaking. Biryukov's APU drawings are shown in Fig.

1. galvanized roof rotor;
2. self-aligning double row ball bearing;
3. cables - 5 mm steel cable;
4. shaft axis - steel pipe with a wall thickness of 1.5-2.5 mm;
5. aerodynamic speed control levers;
6. speed governor blades - 3-4 mm plywood or sheet plastic;
7. rods of the speed regulator;
8. the load of the speed controller, its weight determines the speed;
9. drive pulley - a bicycle wheel without a tire with a tube;
10. thrust bearing - thrust bearing;
11. driven pulley - standard generator pulley;
12. generator.

Biryukov received several copyright certificates for his APU. First, notice the section of the rotor. During acceleration, it works like an aircraft, creating a large starting moment. As the spin progresses, a vortex cushion is created in the outer pockets of the blades. From the wind point of view, the blades become profiled and the rotor turns into a high-speed orthogonal, with the virtual profile changing according to the wind strength.

Secondly, the profiled channel between the blades in the operating speed range acts as a central body. If the wind increases, then a vortex cushion is also created in it, extending beyond the rotor. The same vortex cocoon appears as around the APU with the guide vanes. The energy for its creation is taken from the wind, and it is no longer enough for the breakdown of the windmill.

Thirdly, the speed controller is designed primarily for the turbine. He keeps her turnover optimal from the point of view of KIEV. And the optimum generator speed is ensured by choosing the gear ratio of the mechanics.

Note: after publications in the IR for 1965, the Armed Forces of Ukraine, Biryukova sank into oblivion. The author did not receive a response from the authorities. The fate of many Soviet inventions. They say that some Japanese became a billionaire, regularly reading Soviet popular technical magazines and patenting everything that deserves attention.

Blades

As stated above, a horizontal vane-rotor wind turbine is the best in the classics. But, firstly, it needs a stable, at least medium-strength wind. Secondly, the construction for the DIYer is fraught with a lot of pitfalls, which is why often the fruit of long hard work, at best, illuminates the toilet, hallway or porch, or even turns out to be only able to untwist itself.

According to the diagrams in Fig. let's take a closer look; positions:

• FIG. AND:

1. rotor blades;
2. generator;
3. generator bed;
4. protective weather vane (hurricane shovel);
5. current collector;
6. chassis;
7. swivel knot;
8. working weather vane;
9. mast;
10. clamp for cables.

• FIG. B, top view:

1. protective weather vane;
2. working weather vane;
3. spring tension regulator of the protective vane.

• FIG. G, current collector:

1. a collector with continuous copper ring busbars;
2. spring loaded copper-graphite brushes.

Note: hurricane protection for a horizontal blade with a diameter of more than 1 m is absolutely necessary, because he is not capable of creating a vortex cocoon around himself. With smaller dimensions, rotor endurance of up to 30 m / s can be achieved with propylene blades.

So where are the stumbling blocks?

Blades

Expect to achieve a power on the generator shaft of more than 150-200 W on blades of any span, cut from a thick-walled plastic pipe, as is often advised, are the hopes of a hopeless amateur. A pipe blade (unless it is so thick that it is simply used as a blank) will have a segmented profile, i.e. its top, or both, will be circular arcs.

Segment profiles are suitable for an incompressible medium, such as hydrofoils or propeller blades. For gases, a blade of variable profile and pitch is needed, for example, see fig.; span - 2 m. It will be a complex and time-consuming product, requiring painstaking calculation fully armed with theory, blowing in a pipe and full-scale tests.

Generator

When the rotor is mounted directly on its shaft, the standard bearing will soon break - the same load on all blades in wind turbines does not happen. You need an intermediate shaft with a special support bearing and a mechanical transmission from it to the generator. For large wind turbines, a self-aligning double-row bearing is taken; in the best models - three-tiered, Fig. D in Fig. above. This allows the rotor shaft not only to bend slightly, but also to move slightly from side to side or up and down.

Note: it took about 30 years to develop a thrust bearing for the EuroWind APU.

Emergency weather vane

The principle of its operation is shown in FIG. C. The wind, increasing, presses on the shovel, the spring stretches, the rotor warps, its revolutions drop, and in the end it becomes parallel to the flow. Everything seems to be fine, but it was smooth on paper ...

On a windy day, try holding a boil lid or a large saucepan by the handle parallel to the wind. Only carefully - a fidgety piece of iron can hit the face in such a way that it rubs the nose, cuts the lip, or even knocks out the eye.

Flat wind occurs only in theoretical calculations and, with sufficient accuracy for practice, in wind tunnels. In reality, a hurricane windmills with a hurricane shovel mangle more than completely defenseless ones. It's better to change the warped blades, than to do everything again. In industrial installations, it is another matter. There, the pitch of the blades, one at a time, is monitored and adjusted by automation under the control of an on-board computer. And they are made from heavy-duty composites, not water pipes.

Current collector

This is a regularly serviced site. Any power engineer knows that a collector with brushes needs to be cleaned, lubricated, and adjusted. And the mast is from a water pipe. You will not get in, once a month or two you will have to throw the whole windmill on the ground and then raise it again. How long will he last from such "prevention"?

Video: bladed wind generator + solar panel for power supply of the summer cottage

Mini and micro

But with a decrease in the size of the vane, the difficulties fall along the square of the wheel diameter. It is already possible to manufacture a horizontal vane APU on our own for a power of up to 100 W. A 6-blade one would be optimal. With more blades, the rotor diameter for the same power will be smaller, but it will be difficult to secure them firmly on the hub. Rotors with less than 6 blades can be ignored: a 100 W 2-blade needs a 6.34 m diameter rotor, and a 4-blade of the same power needs 4.5 m. For a 6-blade, the power - diameter dependence is expressed as follows :

• 10 W - 1.16 m.
• 20 W - 1.64 m.
• 30 W - 2 m.
• 40 W - 2.32 m.
• 50 W - 2.6 m.
• 60 W - 2.84 m.
• 70 W - 3.08 m.
• 80 W - 3.28 m.
• 90 W - 3.48 m.
• 100 W - 3.68 m.
• 300 W - 6.34 m.

The best will be to count on a power of 10-20 watts. First, a plastic blade with a span of more than 0.8 m will not withstand winds exceeding 20 m / s without additional protection measures. Secondly, with a blade span up to the same 0.8 m, the linear speed of its ends will not exceed the wind speed by more than three times, and the requirements for profiling with twist are reduced by orders of magnitude; here a "trough" with a segmented profile from a pipe, pos. B in Fig. And 10-20 W will provide power to the tablet, recharge the smartphone or light up the housekeeping light.

Next, select the generator. A Chinese motor is perfect - a wheel hub for electric bicycles, pos. 1 in fig. Its power as a motor is 200-300 W, but in generator mode it will give about 100 W. But will it suit us in terms of turnover?

The speed index z for 6 blades is 3. The formula for calculating the rotational speed under load is N \u003d v / l * z * 60, where N is the rotational speed, 1 / min, v is the wind speed, and l is the rotor circumference. With a blade span of 0.8 m and a wind of 5 m / s, we get 72 rpm; at 20 m / s - 288 rpm. The bicycle wheel rotates at about the same speed, so we will remove our 10-20 watts from a generator capable of giving 100. You can put the rotor directly on its shaft.

But here the following problem arises: we, having spent a lot of labor and money, at least for a motor, got ... a toy! What is 10-20, well, 50 watts? And you can't make a bladed wind turbine capable of powering at least a TV at home. Is it possible to buy a ready-made mini-wind generator, and will it cost less? As much as possible, and even as cheaper, see pos. 4 and 5. In addition, it will also be mobile. Put it on a stump - and use it.

The second option is if a stepper motor is lying somewhere from an old 5- or 8-inch drive, or from a paper drive or a carriage of an unusable inkjet or dot matrix printer. It can work as a generator, and it is easier to attach a carousel rotor from cans (pos. 6) to it than to assemble a structure like that shown in pos. 3.

On the whole, the conclusion about the “blades” is unambiguous: self-made ones are more likely to be mastered, but not for real long-term energy output.

Video: the simplest wind generator for lighting a summer cottage

Sailboats

A sailing wind generator has been known for a long time, but the soft panels of its blades (see Fig.) Began to be made with the advent of high-strength, wear-resistant synthetic fabrics and films. Multi-blade windmills with rigid sails are widely distributed around the world as a drive for low-power automatic water pumps, but their technical data are lower even than those of carousels.

However, a soft sail like the wing of a windmill does not seem to be so simple. It's not about wind resistance (manufacturers do not limit the maximum permissible wind speed): sailing yachts already know that it is almost impossible for the wind to break the Bermuda sail. Rather, the sheet will rip out, or the mast will break, or the whole vessel will make a "turn overkill". It's about energy.

Unfortunately, no precise test data can be found. According to user reviews, it was possible to draw up "synthetic" dependencies for the installation of a wind turbine-4.380 / 220.50 made in Taganrog with a wind wheel diameter of 5 m, a wind head weight of 160 kg and a rotational speed of up to 40 rpm; they are shown in Fig.

Of course, there can be no guarantees for 100% reliability, but even so it is clear that there is no sign of a flat-mechanistic model here. In no way can a 5-meter wheel on a flat wind of 3 m / s give about 1 kW, at 7 m / s reach a plateau in power and then hold it until a severe storm. Manufacturers, by the way, declare that nominal 4 kW can be obtained at 3 m / s, but when installed by their forces according to the results of local aerology studies.

There is no quantitative theory either; the developers' explanations are obscure. However, since the people buy the Taganrog wind turbines and they work, it remains to assume that the declared conical circulation and the propulsive effect are not fiction. In any case, they are possible.

Then, it turns out, BEFORE the rotor, according to the law of conservation of momentum, there should also be a conical vortex, but expanding and slow. And such a funnel will drive the wind to the rotor, its effective surface will turn out to be more swept, and KIEV - over-unit.

Light on this question could be shed by field measurements of the pressure field in front of the rotor, at least with a household aneroid. If it turns out to be higher than from the sides to the side, then, indeed, sailing APUs work like a beetle flies.

Homemade generator

From what has been said above, it is clear that it is better for home-builders to take on either verticals or sailboats. But both are very slow, and transferring to a high-speed generator is unnecessary work, unnecessary costs and losses. Can you make an efficient low-speed electric generator yourself?

Yes, you can, with magnets made of niobium alloy, the so-called. super magnets. The manufacturing process of the main parts is shown in Fig. Coils - each of 55 turns of copper 1 mm wire in heat-resistant high-strength enamel insulation, FEMM, PETV, etc. The height of the windings is 9 mm.

Pay attention to the keyways in the rotor halves. They must be located so that the magnets (they are glued to the magnetic circuit with epoxy or acrylic) after assembly come together with opposite poles. "Pancakes" (magnetic circuits) must be made of a soft magnetic ferromagnet; regular structural steel will do. The thickness of the "pancakes" is at least 6 mm.

In general, it is better to buy magnets with an axial hole and tighten them with screws; super magnets attract with terrible force. For the same reason, a cylindrical spacer 12 mm high is put on the shaft between the "pancakes".

The windings that make up the stator sections are connected according to the diagrams also shown in Fig. The soldered ends should not be stretched, but should form loops, otherwise the epoxy, which will be flooded with the stator, hardening, may break the wires.

The stator is poured into the mold to a thickness of 10 mm. There is no need to center and balance, the stator does not rotate. The gap between the rotor and the stator is 1 mm on each side. The stator in the generator housing must be securely fixed not only against axial displacement, but also against turning; a strong magnetic field with a current in the load will pull it along.

Video: DIY wind turbine generator

Output

And what do we have in the end? Interest in "blades" is explained rather by their spectacular appearance than by the actual performance in a homemade design and at low power. A self-made carousel APU will provide "standby" power for charging a car battery or supplying power to a small house.

But with the sailing APU, it is worth experimenting with craftsmen with a creative streak, especially in a mini version, with a wheel of 1-2 m in diameter. If the assumptions of the developers are correct, then it will be possible to remove from this, using the Chinese engine-generator described above, all of its 200-300 watts.

Andrey said:

Thank you for your free consultation ... And the prices "from firms" are not really expensive, and I think that artisan people from the provinces will be able to make generators similar to yours. And Li-po batteries can be ordered from China, inverters in Chelyabinsk are very good (with smooth sine) .And sails, blades or rotors - this is another reason for the flight of thought of our handy Russian men.

Ivan said:

question:
For wind turbines with a vertical axis (position 1) and the “Lenz” version, it is possible to add an additional detail - an impeller that is exposed to the wind and closes the useless side from it (going in the direction of the wind). That is, the wind will not slow down the blade, but this “screen”. Setting in the wind with the "tail" located behind the windmill itself below and above the blades (ridges). I read the article and an idea was born.

By clicking the "Add comment" button, I agree to the site.

Types of wind turbines

Most types of wind turbines have been known for so long that history is silent on the names of their inventors. The main types of wind turbines are shown in Fig. 13. They are divided into two groups:

1. wind turbines with a horizontal axis of rotation (vane) (2-5);

2. wind turbines with a vertical axis of rotation (carousel: blade (1) and orthogonal (6)).

The types of vane wind turbines differ only in the number of blades.

Vane

For vane-type wind turbines, the highest 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 operate in any wind direction without changing their position. The coefficient of utilization of wind energy in vane-type wind turbines is much higher than that of carousel. At the same time, carousels have much more torque. It is maximum for rotary vane units at zero relative wind speed. The spread of vane wind turbines is explained by the magnitude of their rotation speed. They can be directly connected to an electric current generator without a multiplier. The rotational speed of vane-type wind turbines is inversely proportional to the number of wings, therefore, units with more than three blades are practically not used.

Carousel

The difference in aerodynamics gives the carousel an advantage over traditional wind turbines. As the wind speed increases, they quickly build up the thrust force, after which the rotation speed stabilizes. Carousel wind turbines are slow-moving and this allows the use of simple electrical circuits, for example, with an asynchronous generator, without the risk of an accident due to 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 - a step-up gearbox is not effective due to the low efficiency of the latter. An even more important advantage of the carousel design is its ability to keep track of “where the wind is blowing from” without additional tweaks, 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 the 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.

Orthogonal

Orthogonal wind turbines, as experts believe, are promising for large power engineering. Today, wind worshipers of orthogonal structures face certain difficulties. Among them, in particular, the launch problem. In orthogonal installations, the same wing profile is used as in a subsonic aircraft (see Fig. 13. (6)). The airplane must take a run before it can "lean" on the lift of the wing. The same is the case with the orthogonal setup. First, it is necessary to supply energy to it - to spin it up and bring it to certain aerodynamic parameters, and only then it will itself switch from engine mode to generator mode. Power take-off begins at a wind speed of about 5 m / s, and the rated power is achieved at a speed of 14-16 m /from. Preliminary calculations of wind turbines provide for their use in the range from 50 to 20,000 kW. In a realistic installation with a power of 2000 kW, the diameter of the ring along which the wings move will be about 80 meters. The powerful wind turbine has large dimensions. However, you can get by with small ones - take a number, not a size. By equipping each generator with a separate converter, the output power generated by the generators can be summed up. In this case, the reliability and survivability of the wind turbine is increased.

Industrial wind turbine operation problems

An industrial wind turbine is built on a prepared site in 7-10 days. Obtaining regulatory approvals for the construction of a wind farm can take a year or more. Construction requires a road to the construction site, a place for placing units during installation, heavy lifting equipment with an extension of the boom of more than 50 meters, since gondolas are installed at a height of about 50 meters. During the operation of industrial wind turbines, various problems arise:

· Incorrect foundation arrangement. If the foundation of the tower is incorrectly calculated, or the drainage of the foundation is improperly arranged, the tower may fall from a strong gust of wind.

· Icing of the blades and other parts of the generator. Icing can increase the mass of the blades and reduce the efficiency of the wind generator. For operation in the arctic regions, parts of the wind turbine must be made of special frost-resistant materials. The fluids used in the generator must not freeze. Equipment that measures wind speed may freeze. In this case, the efficiency of the wind generator can be seriously reduced. Due to icing, the instruments may display low wind speeds and the rotor will remain stationary.

· Lightning strikes. Lightning strikes can cause a fire. Lightning protection systems are installed on modern wind turbines.

· Shutdown. With sharp fluctuations in wind speed, the electrical protection of the devices included in the system is triggered, which reduces the efficiency of the system as a whole. Also, for large wind farms, there is a high probability of activation of protection on outgoing power lines.

· Instability of the generator. Due to the fact that in most industrial wind power plants there are asynchronous generators, their stable operation depends on the constancy of the voltage in the transmission line.

· Fires. A fire can be caused by friction of rotating parts inside the nacelle, oil leakage from hydraulic systems, broken cables, etc. Wind turbine fires are rare, but difficult to extinguish due to the remoteness of wind farms and the high altitude at which the fire occurs. Fire extinguishing systems are installed on modern wind turbines

Currently, there are many wind turbine systems with both horizontal and vertical axis of rotation. They differ from each other not only in appearance and device, but also in technical capabilities, depending on the purpose for which they are used. According to the device of the wind energy receiver and its location in the air flow, several wind turbine systems are distinguished.

We have already talked about carousel and drum wind turbines. The so-called rotary wind turbine is also known (Fig. 23). Its blades rotate, like a carousel wind turbine, in a horizontal plane and set in motion a vertical shaft.

Figure: 23. Rotary wind turbine

Vane-wheel wind turbines are widespread today, the most ancient type of which are ordinary windmills. The main part of any vane wind turbine is the wind wheel. It consists of several blades and rotates under the influence of the wind. With the help of a pair of bevel gears mounted on the wind turbine head (Fig. 24), the rotation of the wheel turns into a faster movement of the vertical shaft or into a reciprocating movement of the drive rod.

Figure: 24. Vane-type wind turbine diagram

For turning the head and wind wheel into the wind, windmills have a carrier, and modern small wind turbines have a tail with a vertical tail at the end. Large vane wind turbines have other more complex mechanisms for automatically setting the wind wheel to the wind. So that the speed of rotation of the wind wheel does not exceed the limit, there is a special device for automatic control of the speed.

Usually, at the surface of the earth, the air flow due to various obstacles is uneven, weakened, so the wind wheel is installed on a high mast or tower, above the obstacles.

According to the structure of wind wheels, modern vane wind turbines are divided into high-speed and low-speed.

In a low-speed wind turbine, the wind wheel consists of a large number of blades (Fig. 25). It gets under way easily. Thanks to this, the low-speed wind turbine is convenient for working with a piston pump and other machines that require a large initial effort when starting up.

Figure: 25. Modern multi-blade wind turbine TB-5 with a capacity of up to 2.5 horsepower

Slow-speed wind turbines are mainly used in areas where the average wind speed does not exceed 4.5 meters per second. All mechanisms of multi-layer wind turbines, as a rule, are somewhat simpler than those of high-speed ones. However, the wind wheels of low-speed wind turbines are rather bulky structures. With the large dimensions of these wheels, it is difficult to create the necessary stability, especially at high wind speeds. Therefore, at present, multi-blade wind turbines are being built with wind wheel diameters of no more than 8 meters. The power of such a wind turbine reaches 6 horsepower. This capacity is quite enough to supply water to the surface from wells up to 200 meters deep.

High-speed wind turbines have no more than four wings with a streamlined profile in the wind wheel (see, for example, Fig. 27).

Figure: 27. Wind turbine 1-D-18 with a capacity of up to 30 kilowatts

This enables them to withstand very strong winds well. Even in strong and gusty winds, well-designed control mechanisms ensure uniform rotation of the wind wheels of high-speed wind turbines.

These positive features of high-speed wind turbines allow them to operate in variable winds of any strength.

Therefore, high-speed wind turbines can be built with very large wind wheel diameters, reaching fifty meters or more and developing a power of several hundred horsepower.

Due to the high and stable uniformity of the wind wheels, high speed wind turbines are used to drive a wide variety of machines and electrical generators. Modern high-speed wind turbines are versatile machines.

It is convenient to compare wind turbines of various systems by introducing the concept of normal speed. This speed is determined by the ratio of the peripheral speed at the outer end of the rotating blade at a wind speed of 8 meters per second to the air speed.

The blades of carousel, rotary and drum wind turbines during operation move along the air flow and the speed of any point on them can never exceed the wind speed. Therefore, the normal speed of these types of wind turbines will always be less than one (since the numerator will be less than the denominator).

The wind wheels of vane wind turbines rotate across the direction of the wind, and therefore the speed of movement of the end parts of their wings reaches high values. It can be several times higher than the air flow rate. The smaller the blades and the better their profile, the less resistance the wind wheel experiences. This means that the faster it rotates. The best examples of modern vane-type wind turbines have a normal speed of up to nine units. Most factory-made wind turbines have a speed of 5-7 units. For comparison, we note that even the best peasant mills had a speed equal to only 2-3 units (and in this sense they are more advanced than carousel, rotary and drum wind turbines).

With an increase in the number of blades at a wind wheel, its ability to get under way at low wind speeds increases. Therefore, multi-blade vane wind turbines, in which the total area of \u200b\u200bthe blades is 60-70 percent of the swept surface (see Fig. 20) of the wind wheel, come into operation at wind speeds of 3-3.5 meters per second.

Figure: 20. Gantry mill

High-speed wind turbines with a small number of blades get under way at wind speeds of 4.5 to 6 meters per second. Therefore, they have to be put into operation either without load or with the help of special devices.

The good start-off and the simplicity of the design of the carousel, rotary and drum wind turbines win over many inventors and designers who consider them to be ideal wind turbines. In reality, however, these machines have a number of significant disadvantages. These disadvantages make them difficult to use even with such common and simple machines as piston pumps and burr mills.

Wind turbines with rotary-type wind energy receivers use the energy of the air flow very poorly, their wind energy utilization coefficient is 2-2.5 times less than that of vane wind turbines. Therefore, with equal surfaces swept by the blades, vane wind turbines can develop a power 2-2.5 times greater than carousel, rotary and drum wind power plants.

Rotary-type wind turbines are currently used only in the form of small artisanal installations with a capacity of up to 0.5 horsepower. For example, they are used to drive various ventilation devices in livestock houses, forges and other production areas in agriculture.

What determines the power of a wind turbine?

We know that the energy of the air flow is not constant, so any wind turbine has variable power. The power of any wind turbine depends on the wind speed. It was found that when the wind speed doubles, the power on the wings of the wind turbine increases 8 times, and when the air flow speed grows 3 times, the power of the wind turbine increases 27 times.

The power of the wind turbine also depends on the size of the wind energy receiver. In this case, it is proportional to the area swept by the blades of the wind wheel or rotor. For example, for vane wind turbines, the surface swept by the blades will be the area of \u200b\u200ba circle that describes the end of the blade in one full revolution. In drum, carousel and rotary wind turbines, the surface swept by the blades is the area of \u200b\u200ba rectangle with a height equal to the length of the blade and a width equal to the distance between the outer edges of the opposite blades.

However, any wind wheel or rotor converts into useful mechanical work only a fraction of the energy of the air flow passing through the surface being swept by the blades. This part of the energy is determined by the utilization rate of wind energy. The value of the coefficient of utilization of wind energy is always less than one. In the best modern high-speed wind turbines, this coefficient reaches 0.42. For serial factory high-speed and low-speed wind turbines, the coefficient of wind energy utilization is usually 0.30-0.35; this means that only about one third of the energy of the air flow passing through the wind wheels of wind turbines is converted into useful work. The remaining two-thirds of the energy remains unused.

The Soviet scientist G. Kh. Sabinin, on the basis of calculations, established that even an ideal wind turbine has a wind energy utilization factor of only 0.687.

Why can't this coefficient be equal or even close to one?

This is explained by the fact that part of the wind energy is spent on the formation of vortices near the blades and the wind speed behind the wind wheel decreases.

Thus, the actual power value of the wind turbine depends on the utilization rate of wind energy. The power of the wind turbine is proportional to its value. This means that with an increase in the utilization of wind energy, the power of the wind turbine increases, and vice versa.

Drum, carousel and rotary wind turbines with the simplest blades have very low wind energy utilization rates. Their values \u200b\u200brange widely from 0.06 to 0.18. For vane engines, this coefficient is in the range from 0.30 to 0.42.

In addition, the net power of any wind turbine is also proportional to the efficiency of the transmission mechanism, as well as to the air density. Typically, the efficiency of the mechanisms of modern wind turbines is from 0.8 to 0.9.

From what has been said about the power of the wind turbine, it follows that with a given wind, that wind engine will have a higher power, in which the largest amount of air flow flows through the surface swept by the wings, and the blades of the wind wheel have a well streamlined profile.

a device that converts wind energy into rotational energy. The main working body of a 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 installed horizontally or vertically. Wind turbines are usually used to generate energy that is consumed periodically: when pumping water into containers, grinding grain, in temporary, emergency and local power supply networks. Historical reference. Although surface winds do not always blow, change their direction and their strength is unstable, the wind turbine is one of the oldest machines for obtaining energy from natural sources. Due to the dubious reliability of ancient written reports of wind turbines, it is not entirely 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 of the Dutch windmill was finally formed. Special changes in their design were not observed until the beginning of the 20th century, when, as a result of research, the shapes and coatings of the mill wings were significantly improved. Since low-speed machines are cumbersome, in the second half of the 20th century. they began to build high-speed wind turbines, i.e. those, the wind wheels of which can make a large number of revolutions per minute with a high utilization of wind energy. Modern types of wind turbines. Currently, there are three main types of wind turbines - drum, vane (screw type) and rotary (with an S-shaped repeller profile). Drum and vane. Although the drum type wind turbine has the lowest wind power utilization rate compared to other modern repellers, it is the most widely used. On many farms, it is used to pump water if for any reason there is no mains electricity. A typical shape for such a wheel with sheet metal blades is shown in Figure 1. Drum-type and vane-type windwheels rotate on a horizontal shaft, so they must be turned into 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 turn of the wind wheel to the wind. The wheel diameter of the world's largest vane-type wind turbine is 53 m, and its maximum blade width is 4.9 m. The wind wheel is directly connected to a 1000 kW electric generator, which develops at a wind speed of at least 48 km / h. Its blades are regulated in such a way that the rotation speed of the wind turbine remains constant and equal to 30 rpm in the wind speed range from 24 to 112 km / h. Due to the fact that in the area where such wind turbines are located, the winds blow quite often, the wind turbine usually generates 50% of its maximum power and powers the public grid. Vane-type wind turbines are widely used in remote rural areas to provide power to farms, including charging batteries for radio communication systems. They are also used in airborne power plants of aircraft 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 out to the wind. Although the torque on its shaft changes from a minimum to one third of the maximum value in half a turn, it does not depend on the direction of the wind. When a smooth circular cylinder rotates under the influence of the wind, a force perpendicular to the direction of the wind acts on the body of the cylinder. This phenomenon is called the Magnus effect, after the German physicist who studied it (1852). In 1920-1930 A. Flettner used rotating cylinders (Flettner's rotors) and S-shaped rotors instead of bladed wind wheels, as well as propellers of a ship that made the transition from Europe to America and back. Wind energy utilization factor. The power derived from the wind is usually small - less than 4 kW is developed by an older type of Dutch windmill at a wind speed of 32 km / h. The power of the wind flow that can be used is formed from the kinetic energy of air masses sweeping per unit of time perpendicular to an area of \u200b\u200ba given size. In a wind turbine, this area is determined by the windward surface of the repeller. 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 utilization factor 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 turbine. This coefficient becomes maximum at a certain ratio between the speed of the outer edge of the propeller blade w and the wind speed u; the value of this ratio w / u depends on the type of wind turbine. The wind energy utilization factor depends on the type of wind turbine and ranges from 5-10% (Dutch mill with flat wings, w / u \u003d 2.5) to 35-40% (profiled vane repeller, 5? W / u? 10).