Systems of modern wind turbines. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

 Comments on the article

Currently, there are many wind turbine systems, both with 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 design of the wind energy receiver and its location in the air flow, several systems of wind turbines are distinguished.

We have already talked about carousel and drum type 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.

Fig.23. Rotary wind turbine

Vane wind turbines are now widely used, 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 head of the wind turbine (Fig. 24), the rotation of the wheel is converted into a faster movement of the vertical shaft or into the reciprocating movement of the drive rod.

Fig.24. Scheme of a vane wind turbine

To turn the head and the wind wheel into the wind, windmills have a carrier, and modern small wind turbines have a tail with vertical plumage at the end. In large vane wind turbines, there are other more complex mechanisms for automatically setting the wind wheel into the wind. To ensure that the speed of rotation of the wind wheel does not exceed the limit, there is a special device for automatic regulation of the number of revolutions.

Usually, near 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 arrangement of wind wheels, modern vane wind turbines are divided into high-speed and low-speed ones.

In a low-speed wind turbine, the wind wheel consists of a large number of blades (Fig. 25). It moves easily. Due to this, a low-speed wind turbine is convenient for working with a piston pump and other machines that require a large initial force during start-up.

Fig.25. Modern multi-bladed 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 multilayer 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 large sizes of such wheels, it is difficult to create the necessary stability, especially at high wind speeds. Therefore, at present, multi-blade wind turbines are built with wind wheel diameters of no more than 8 meters. The power of such a wind turbine reaches 6 horsepower. This power 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).

Fig.27. Wind turbine 1-D-18 with a power of up to 30 kilowatts

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

These positive features of high-speed wind turbines allow them to work with a variable wind of any strength.

Therefore, high-speed wind turbines can be built with very large wind wheel diameters, reaching fifty or more meters 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 universal 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 speed of the air flow.

The blades of carousel, rotary and drum wind turbines during operation move along the air flow and the speed of any of their points can never be greater than the wind speed. Therefore, the normal speed of wind turbines of these types 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 large values. It can be several times the speed of the air flow. The smaller the blades and the better their profile, the less resistance the wind wheel experiences. So the faster it spins. The best samples of modern vane wind turbines have a normal speed, reaching nine units. Most factory-made wind turbines have a speed equal to 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 rotary, rotary and drum wind turbines).

With an increase in the number of blades at the wind wheel, its ability to start at low wind speeds increases. Therefore, multi-bladed impeller wind turbines, in which the total area of ​​​​the 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.

Fig.20. Gantry mill

High-speed wind turbines with a small number of blades start moving at wind speeds from 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.

Good starting and simplicity of design of carousel, rotary and drum wind turbines bribe many inventors and designers who consider them to be ideal wind turbines. In reality, however, these machines have a number of significant drawbacks. These shortcomings make them difficult to use even with common and simple machines such as piston pumps and burr grinders.

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 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 handicraft installations with a capacity of up to 0,5 horsepower. For example, they are used to drive various ventilation devices in livestock buildings, forges and other industrial premises 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 a variable power. The power of any wind turbine depends on the wind speed. It has been established that when the wind speed doubles, the power on the wind turbine wings increases by 8 times, and when the air flow speed increases by 3 times, the wind turbine power increases by 27 times.

The power of the wind turbine also depends on the size of the receiver of wind energy. In this case, it is proportional to the area covered by the blades of the wind wheel or rotor. For example, in vane wind turbines, the surface swept by the blades will be the area of ​​a circle that describes the end of the blade in one complete revolution. In drum, carousel and rotary wind turbines, the surface swept by the blades is the area of ​​a 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 only a part of the energy of the air flow passing through the surface swept by the blades into useful mechanical work. This part of the energy is determined by the utilization factor of wind energy. The value of the wind energy utilization factor is always less than one. For the best modern high-speed wind turbines, this coefficient reaches 0,42. For serial factory high-speed and low-speed wind turbines, the wind energy utilization factor is usually 0,30-0,35; this means that approximately only 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, found that even an ideal windmill has a wind energy utilization factor of only 0,687.

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

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 drops.

Thus, the actual value of the wind turbine power depends on the wind energy utilization factor. The power of a wind turbine is proportional to its value. This means that with an increase in the coefficient of use 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 ​​vary 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 useful power of any wind turbine is also proportional to the efficiency of the transmission mechanism, as well as 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 turbine will have a higher power, in which the largest amount of air flows through the surface swept by the wings, and the blades of the wind wheel have a well-streamlined profile.

Author: Karmishin A.V.

See other articles Section Alternative energy sources.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Major risk factor for gambling addiction 07.05.2024

Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Random news from the Archive PHILIPS OM6777 Stereo Wireless Headset 25.07.2005 Philips has unveiled a new reference design for its Bluetooth 1.2 wireless headset. The device provides stereo sound and voice transmission. With it, you can listen to music played on your portable player or mobile phone without the risk of missing a phone call. The need for an all-in-one wireless headset is growing as the market for high quality mobile audio and video players expands and the integration of related capabilities into cell phones. The development uses Philips Lifevibes Voice and LifeVibes Music technologies, which improve the sound quality. LifeVibes Voice performs noise reduction and enhances speech intelligibility even in noisy environments, while LifeVibes Music enhances stereo reproduction in audio recordings and dynamically adjusts bass boost. The wireless headset, designated OM6777, is designed for plug-and-play use and is based on a proven stereo codec for audio streaming. An exemplary design will allow manufacturers who choose it as the basis for their end-user products to concentrate on their external design without worrying about the details of the technical implementation of functions. The design uses the Philips Bluetooth BGB203/4 HCI element set, optimized for mobile applications due to power consumption and miniature size.

Other interesting news:

▪ Arlo Q IP Camera

▪ Flying robot the size of an insect

▪ Optical discs are getting more expensive

▪ Self-hypnosis or allergies

▪ iPhone SDH Released

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section And then an inventor (TRIZ) appeared. Article selection

▪ article Rocketplane S-4-D. Tips for a modeller

▪ article What keeps the Moon in Earth orbit? Detailed answer

▪ article Work on sterilizers (dry ovens). Standard instruction on labor protection

▪ article A little about the GPA. Encyclopedia of radio electronics and electrical engineering

▪ article Renegative AM-FM receiver. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024