Small wind generators for home. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

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Wind energy is an environmentally friendly, inexhaustible energy. Wind power plants (mills, wind turbines) are used to convert wind energy into electrical energy.

Windmills used to generate electricity come in a variety of sizes. Large wind turbines, which are commonly used in wind farms (power plants), can generate large amounts of electricity - hundreds of megawatts, which can be supplied to hundreds of homes. Small wind turbines, which produce no more than 100 kW of electricity, are used in private houses, farms, household plots, etc., serve as a source of additional electricity, and help reduce the payment for the main source of electricity.

Very small windmills with a power of 20-500 W are used for recharging batteries and other applications where a large amount of electricity is not required.

Small wind farms will be cost effective if the following conditions are met:

• the wind in your location blows steadily and many days a year;
• there is enough space to install a windmill;
• local authorities allow the installation of windmills;
• your energy costs are high;
• you are not connected to the power supply or it is far from you;
• Are you ready to invest in a wind turbine?
• in order to avoid problems with neighbors, the windmill should be no closer than 250-300 m to them.

wind requirements

Whether your windmill for your home will be economically viable depends most of all on the quality of the wind. In most cases, an average annual wind speed of 4.0-4.5 m/s (14.4-16.2 km/h) is the minimum for a wind turbine to be economically viable. In the analysis of the wind you will be helped by sites where maps of the winds of Russia and other countries are presented.

Also, the local meteorological station can help you, where you can look at the archive of wind strength data. But you should pay attention to the location of the station, because. various obstacles - trees, buildings, hills can cause distorted wind data.

For a more accurate assessment of the wind in your area, you need to purchase devices that measure wind speed. This is especially true if your area is hilly or has an unusual landscape.

The most important part of a wind speed measuring instrument is the anemometer. It consists of a cup (or paddle) turntable mounted on an axle, which is connected to a measuring mechanism. The anemometer blades rotate and produce a signal proportional to the wind speed. When buying an anemometer, it will not be superfluous to purchase a device that records readings from it, as well as a tripod, bracket, etc., where it will be mounted.

There are more expensive digital devices for measuring wind speed. An anemometer is also used there, but the data is sent to a computer, where it is processed and stored. Recently, these devices have become more and more popular and cheaper. You can see an example of wind speed data taken and displayed in real time on the website gdeduet.ru

It doesn't matter what measuring instrument you use to estimate wind speed, but at least once a year you should compare your data with others. It is also important to place the measuring equipment high enough to avoid the turbulence created by trees, buildings and other obstructions. The most optimal placement of the measuring device is its placement at the level of the center of the wind turbine rotor.

Location for a wind turbine

Of great importance is the place where you are going to place your windmill. Remember that you should not place it near trees, houses, etc., because. you won't get the full benefit of a windmill.

Also keep in mind that:

• wind strength is always greater on top of hills, along the coastline, in the steppes, in places where there are no trees and buildings.
• trees can grow, but a windmill cannot.
• it is necessary to inform the neighbors in advance about your plans in order to avoid problems with them in the future.
• it is advisable to put the windmill at a sufficient distance from the neighbors. Usually 250-300m is enough.

Don't expect your wind farm to generate enough electricity all the time. The wind speed in the same place can vary greatly and, as a result, the amount of electricity generated will also vary. And if the wind strength changes within 10%, then the generated electricity will change within 25%!

Types of wind turbines

There are 2 main types of wind turbines: with a horizontal axis of rotation and vertical. Horizontal windmills should be directed downwind. For this, the so-called "tail" is provided in their design.

Vertical wind generators work in any wind direction, but require more ground space, because. it is necessary to provide stretch marks for the stability of the windmill.

wind farm components

The main components of a typical wind farm are shown in the figure below.

They include:

• rotor with blades that have an aerodynamic shape.
• reducer or a gearbox that matches the speed of rotation between the rotor and the generator. Small windmills (up to 10 kW) usually do not have a gearbox.
• protective cover, which protects the gearbox, generator, electronics and other components of the wind generator from external influences.
• tail windmill - necessary to turn it in the wind.

For wind turbines with a horizontal axis of rotation, a mast is required (vertical wind turbines are usually installed directly on the ground).

There are various types of masts: guyed masts (which are rigidly fixed), guyed swivel masts (can be raised and lowered for maintenance and repair), free-standing mast without guys (they are heavy, but they do not take up much space on the ground).

A very important factor is the height of the mast. Wind energy is proportional to the wind speed to the third power (cubed). That. if the wind speed has doubled, then the wind energy will increase 8 times (2x2x2=8) (Figure 6). Wind speed increases with height, i.e. By increasing the height of the mast, you can greatly increase the energy efficiency of the windmill.

The recommended installation height is 24-37 meters. Installing a windmill at a lower height is the same as placing solar panels in the shade.

To be on the safe side, check your local laws for wind turbine mast height restrictions. Use a mast design approved by the windmill manufacturer, otherwise you may void your warranty. Be sure to ground the mast and provide a lightning rod.

For electrical safety, disconnectors and circuit breakers must be used. They will also provide safe access to the windmill for maintenance and upgrades.

Other components of the wind farm may also be needed. Accumulators - will be able to accumulate excess electricity from the windmill. But, since batteries use direct current, to convert it to alternating current, inverter.

If a house, farm or household is connected to a common energy supply system, then on windy days, excess energy can be sold to power grids (irrelevant for our country). And when the wind is weak and there is not enough electricity from the windmill, then you will need to buy electricity from the general power grid.

Wind turbine cost

The cost of a small windmill is $2000-$8000 per 1 kW. However, this is only 12-48% of the cost of all wind farm components: inverters, batteries, chargers, ATS, etc.

But the big plus of a wind turbine is that once you buy it, you will almost never have to pay for anything else, except for scheduled maintenance.

The performance of a wind turbine is usually described by the manufacturer as a graph of power output versus wind speed.

One of the problems when choosing and comparing wind turbines is the lack of a single standard for measuring output power.
Manufacturers themselves choose at what wind speed to indicate output power. Take for example "Wind-o-matic" and "Mighty-wind" - both have a claimed power of 1000 watts. But "Wind-o-matic" is power at 5 m/s, while "Mighty-wind" is power at 10 m/s. Due to the fact that the wind energy is proportional to the cubed wind speed, a windmill producing 1 kW at 10 m/s will only give 1/8 of the maximum power at 5 m/s. That. with a wind speed of 5 m / s, "Wind-o-matic" will produce an honest 1000 kW, while "Mighty-wind" is only 125 watts!

It is more correct to compare wind turbines by area and blade size. The larger the area, the more energy the windmill can generate. Doubling the area of ​​solar panels - the power is doubled. Also in a wind generator - with an increase in the area of ​​\uXNUMXb\uXNUMXbthe blades, the output power increases.

If you don't know the area of ​​the windmill blades, then you can compare by the diameter of the rotor. A slight increase in the diameter of the rotor leads to a significant increase in the output of electricity from the wind turbine (see figure). The values ​​shown in the figure are indicative and should not be relied upon, because The generated power of a wind turbine depends on many other factors.

Wind turbine size selection

To determine the appropriate size of a windmill, first look at how much electricity you consume per month. Then multiply the resulting value by 12 months.

The approximate amount of electricity generated by a windmill you can get by the formula:
AEO = 1.64 * D*D * V*V*V
where: AEO - electricity per year (kWh / year), D - rotor diameter (in meters), V - average annual wind speed (m / s).

That. you can choose the optimal size of the wind generator that produces the necessary power for your home or farm. And it is possible to save on the purchase.

Relations with neighbors

Many people demand a careful attitude to the things around them: landscape, view, historical places, silence, neighbors, etc. Be sure to talk to your neighbors about your plans to install a wind farm. Also, you must understand that people have a fear of something new and unknown.

Many people think that windmills harm birds. But in fact, sliding doors are more dangerous for birds than small windmills. Also, wind turbines have a negligible impact on radio and television broadcasting. The blades of all modern windmills are made of fiberglass or wood. These materials are transparent to electromagnetic waves.

Noise

Neighbors do not accept the noise from the wind turbine. Before you install a wind farm, make your neighbors aware of the noise it can produce:

• aerodynamic noise - arise due to air flows produced by the blades. Noises increase with the speed of rotation of the rotor. Sometimes due to air turbulence, some types of blades can make a whistling sound.
• mechanical noise - may occur in other components of the windmill (generator, gearbox, etc.)

At 250 meters from a typical wind farm, the sound pressure level is approximately 45 dB. Small windmills produce no more noise than air conditioners.

The blades of a small windmill rotate at an average speed of 175-500 rpm, with a maximum of 1150 rpm. Large windmills rotate at a constant speed of 50-15 rpm

Service

Wind farms require constant maintenance - regular inspections, lubrication of rubbing parts, etc. Check bolted connections and electrical contacts annually and retighten if necessary. Also check your windmill for corrosion and mast bracing.

If the blades are made of wood, apply paint for protection. Attach a strong tape to the edges of the blades to protect against abrasive dust and flying insects. If the paint cracks and the film peels off, then an unprotected tree will quickly become unusable. Moisture infiltrating the wood of the blades can cause the rotor to be out of balance. Check windmill blades annually.

After 10 years of operation, the blades and bearings must be replaced. With proper installation and operation, a wind farm can last 30 years or more. Proper maintenance will also minimize the noise level from your windmill.

Security

All wind generators have a maximum wind speed above which they cannot operate. When the wind speed exceeds this value, then the wind generator must operate a brake mechanism that does not allow the critical value to be exceeded.

When using the windmill in cold areas, take care of the problem of icing and place the battery pack in an isolated area.

Installation of a windmill on the roof of a building is not recommended. But if it is of low power (up to 1 kW), then an exception can be made. The fact is that a wind turbine can produce vibration, which can be transmitted to the surface on which it is installed.

Author: Koltykov A.V.; Publication: cxem.net

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