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The Earth is surrounded by the atmosphere, which is made up of air. Air is a mixture of gas, and solid and liquid particles. Energy from the sun heats up the atmosphere and the Earth unevenly.
Cold air contains more air particles than warm air. Cold air is therefore heavier and sinks down through the atmosphere, creating high pressure areas. Warm air rises through the atmosphere, creating low pressure areas. The air tries to balance out the low and high pressure areas &#; air particles move from areas of high pressure (cold air) to areas of low pressure (warm air). This movement of air is known as the wind.
The wind is also influenced by the movement of the earth. As it turns on its axis the air does not travel directly from areas of higher pressure to areas of lower pressure. Instead, the air is pushed to the west in the northern hemisphere and to the east in the southern hemisphere. This is known as the Coriolis force. Click to see a diagram of how the movement of the Earth affects wind.
The Earth's surface is marked with trees, buildings, lakes, sea, hills and valleys, all of which also influence the wind's direction and speed. For example, where warm land and cool sea meet, the difference in temperature creates thermal effects, which causes local sea breezes.
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Wind is usually measured by its speed and direction. Wind atlases show the distribution of wind speeds on a broad scale, giving a graphical representation of mean wind speed (for a specified height) across an area. They are compiled by local meteorological station measurements or other wind-related recorded data.
Traditionally, wind speed is measured by anemometers &#; usually three cups that capture the wind rotating around a vertical axis (pictured below). The wind direction is measured with weather vanes.
After measuring wind data for at least one year, the mean annual wind speed can be calculated. Wind speed and wind direction statistics are visualised in a wind rose, showing the statistical repartition of wind speed per direction.
Wind statistics show the best sites to locate wind farms according to the best wind resources. They also provide further information on how the turbines should be positioned in relation to each other and what the distance between the turbines should be.
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A wind turbine is a machine that transforms the kinetic energy of the wind into mechanical or electrical energy. Wind turbines consist of a foundation, a tower, a nacelle and a rotor. The foundation prevents the turbine from falling over. The tower holds up the rotor and a nacelle (or box).
The nacelle contains large primary components such as the main axle, gearbox, generator, transformer and control system. The rotor is made of the blades and the hub, which holds them in position as they turn. Most commercial wind turbines have three rotor blades. The length of the blades can be more than 60 metres.
See how a wind turbine works!
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The average size of onshore turbines being manufactured today is around 2.5-3 MW, with blades of about 50 metres length. It can power more than 1,500 average EU households.
An average offshore wind turbine of 3.6 MW can power more than 3,312 average EU households.
In , wind turbines were under 1 MW with rotor diameters of around 15 metres.
In , the average size is 2.5 MW with rotor diameters of 100 metres.
7.5 MW turbines are the largest today with blades about 60 metres long &#; over half the length of a rotor diameter of over 120 metres &#; longer than a football field. 15 MW turbines are planned and 20 MW turbines are considered to be theoretically possible.
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The towers are mostly tubular and made of steel or concrete, generally painted light grey. The blades are made of fibreglass, reinforced polyester or wood-epoxy. They are light grey because it is inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.
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There are many factors at play when designing a wind farm. Ideally, the area should be as wide and open as possible in the prevailing wind direction, with few obstacles. Its visual influence needs to be considered &#; few, larger turbines are usually better than many smaller ones.
The turbines need to be easily accessible for maintenance and repair work when needed. Noise levels can be calculated so the farm is compatible with the levels of sound stipulated in national legislation. The turbine supplier defines the minimum turbine spacing, taking into account the effect one turbine can have on others nearby &#; the 'wake effect'.
Then, the right type of turbine must be chosen. This depends on the wind conditions and landscape features of the location, local/national rules such as on turbine height, noise levels and nature conservation, the risk of extreme events such as earthquakes, how easy it is to transport the turbines to the site and the local availability of cranes.
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Construction time is usually very short &#; a 10 MW wind farm can easily be built in two months. A larger 50 MW wind farm can be built in six months.
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Costs vary but the biggest cost is the turbine itself. This is a capital cost that has to be paid up front and typically accounts for 75% of the total.
Once the turbine is up and running there are no fuel and carbon costs, only operation and maintenance costs (O&M), which are minimal compared to e.g. a gas power plant where O&M is 40-70% of total costs, and the rest of the cost is fuel.
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Wind turbines start operating at wind speeds of 4 to 5 metres per second and reach maximum power output at around 15 metres/second. At very high wind speeds, that is gale force winds of 25 metres/second, wind turbines shut down. A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs depending on the wind speed.
Over the course of a year, it will typically generate about 24% of the theoretical maximum output (41% offshore). This is known as its capacity factor. The capacity factor of conventional power stations is on average 50%-80%. Because of stoppages for maintenance or breakdowns, no power plant generates power for 100% of the time.
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The optimum number of blades for a wind turbine depends on the job the turbine has to do. Turbines for generating electricity need to operate at high speeds, but do not need much turning force. These machines generally have three or two blades. On the other hand, wind pumps need turning force but not much speed and therefore have many blades.
The majority of modern commercial wind turbines have three blades, as they produce the optimum amount of power.
Two bladed machines are cheaper and lighter, with higher running speeds which reduces the cost of the gearbox, and they are easier to install. They perform almost as well as three blade turbines. However they can be noisier and are not as visually attractive, appearing 'jerky' when they turn.
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Turbines sometimes have to be stopped for maintenance, for repairing components or if there is a failure that needs to be checked. Another reason can be too little or too much wind: if the wind is too strong, the turbine needs to be shut down because it could be damaged.
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In a wind farm the turbines themselves take up less than 1% of the land area. Existing activities like farming and tourism can take place around them and animals like cows and sheep are not disturbed.
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More and more householders, communities and small businesses are interested in generating their own electricity by using small scale wind turbines, either on their roofs or in their back gardens. If you are interested in how you can power your home or business with your own turbine, then contact your national wind energy association for more information on how this works in your country.
Click here to find your national association.
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Browse through our Members Directory to see a comprehensive list of wind turbine manufacturers.
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At present, onshore wind is more economical than development offshore. Furthermore, offshore wind farms take longer to develop, as the sea is inherently a more hostile environment. To expect offshore to be the only form of wind generation allowed would therefore be to condemn us to miss our renewable energy targets and commitment to tackle climate change.
However, in the coming years, as offshore turbines are manufactured on a larger scale, prices will come down, making offshore wind energy increasingly competitive. Enough wind blows over European seas to power Europe seven times over, making offshore wind a highly viable option to exploit.
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In , there were 70,488 onshore wind turbines and 1,132 offshore turbines across the EU. As technology progresses, turbines are becoming bigger and more efficient as the generation of the same amount of energy can be achieved with fewer machines.
There is currently 19.5 MW of wind power capacity installed per 1,000 km of land area in the EU, with the highest densities in Denmark and Germany. Although 25 of the 27 EU Member States now utilise wind power, there is still a substantial amount of wind power capacity available among countries like France, the UK, and Italy. More&#;.
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Wind turbines can carry on generating electricity for 20-25 years. Over their lifetime they will be running continuously for as much as 120,000 hours. This compares with the design lifetime of a car engine, which is 4,000 to 6,000 hours.
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The blades rotate at anything between 15-20 revolutions per minute at constant speed. However, an increasing number of machines operate at variable speed, where the rotor speed increases and decreases according to the wind speed.
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Last fall, after a ten-year break, the construction of a modern wind farm began again in Estonia. What has changed in wind turbine technology in ten years? How much electricity does one wind turbine produce? Andrus Zavadskis, Technical Manager of Utilitas Wind, answers these and other frequently asked questions about wind turbines.
- What has changed in wind turbine technology in ten years?
Over the past ten years, wind turbine technology has advanced remarkably. Today&#;s wind turbines are bigger and more powerful and, because of that, they are also more efficient electricity producers. The bigger the wind turbine is, the fewer wind turbines we need to get the same amount of electricity. For example, the capacity of one turbine in the Paldiski wind farm, built ten years ago, is 2.5 MW. However, the turbines in the Saarde wind farm, which began construction in November, will have a capacity of 4.3 MW each. Thus, the nine wind turbines of the Saarde wind farm produce more electricity per year than the 18 wind turbines of the Paldiski wind farm. The Utilitas&#; wind farms that are currently under development were designed with turbines that have over 6 MW of capacity.
In addition to the development of technology, society&#;s understanding of the need for renewable energy has also changed. Clean and environmentally friendly energy contributes to cheaper electricity prices and is also important for energy security and independence. Wind turbines are the fastest production equipment to install, in terms of renewable energy, and they provide energy throughout the year.
- Why are wind turbines white in color?
There are mainly three reasons why wind turbines are white: neutral appearance, safety, and technical durability.
When seen from the ground, white is the most neutral color, i.e. the least striking, and it also reflects all other colors and light. But seen from the air, the white color helps wind turbines be more noticeable. This is important both for flight safety and for the safe movement of birds. In order to be visible at night, wind turbines are equipped with lights for flight safety.
In addition, the white color helps to extend the life of wind turbines, because it reflects sunlight. Materials heat up due to solar radiation, and higher temperatures reduce the life of the equipment inside the wind turbines. Also, ultraviolet radiation damages materials over time, so it is beneficial to have most of the UV radiation reflected back from the surface of the wind turbine.
- How much electricity does one wind turbine produce?
How much electricity a single wind turbine produces depends on its size, capacity, and location. Depending on the technology and wind conditions, the capacity factor of modern wind turbines is around 40% to 50%. In better locations with higher wind speeds (for example, offshore or on a windy coast), the capacity factor reaches over 50%. The capacity factor equates to the productivity of the wind turbine. If the wind turbine was able to operate at full capacity all year round, this would mean a 100% capacity factor. In reality, however, the wind does not constantly blow at full speed, which is why wind turbines have a lower capacity factor in reality. The capacity factor is calculated by dividing the annual actual production by the annual theoretical maximum production.
For example, the total capacity of the Saarde wind farm, which will begin to operate in Pärnu this summer, is 39 MW, and the estimated annual production is about 135 GWh, which makes it the most productive wind farm in Estonia. The energy produced at the Saarde wind farm covers the annual electricity needs of all homes in Pärnu County, i.e. more than 40,000 households.
Offshore wind turbines produce a certain amount of electricity almost continuously because they produce electricity at a wind speed of 3 m/s and at a height of a few hundred meters above sea level. Thus, one offshore wind turbine covers the annual electricity needs of nearly 20,000 households. Offshore wind turbines are three to four times more powerful than land-based wind turbines. An offshore wind farm with 80 wind turbines produces roughly 60% of Estonia&#;s annual electricity needs.
- What happens if there is no wind?
Depending on the wind conditions, wind turbines produce energy with variable capacity but, luckily, they do not produce energy in isolation. Estonia has external connections for capacity that is bigger than Estonia&#;s electricity consumption at the coldest time of the year. The region of the Nordic and Baltic countries is large enough that there is never a complete lack of wind in the entire region at the same time. If it happens that a large number of wind turbines are down, for example in the summer, then solar and hydro plants still produce renewable electricity in the region. In addition, there are already storage and fast-starting reserve power plants in the region, and more will be built in the coming years.
We have modeled the volumes of wind electricity production according to wind conditions since and found that by adding two offshore wind farms, new onshore wind farms and solar farms, and storage capacities in Estonia, we would be able to cover 95% of Estonia&#;s annual electricity needs with such a portfolio and to export it at certain times. In order to cover the remaining 5%, it is reasonable to have on-site reserve production capacities in addition to connections. Today, the solution is the existing oil shale boilers but, in the future, biomethane-based or cross-sector coupling solutions can be used (to produce hydrogen and heat from green electricity, charge cars, etc.). The need for reserves is in no way only related to renewable energy solutions &#; keeping certain capacities in reserve is always necessary for any combination of energy production capacities.
- Why do we need wind electricity?
The more electricity we produced from renewable energy, the less we need to use gas and oil shale. Abandoning fossil fuels is necessary to slow down climate change and maintain a livable climate. As electricity consumption increases, for example, due to the growth of electric transport, methods must be found to produce electricity without fossil energy sources.
In Estonia, the best way to produce clean electricity is wind turbines, because we live in a sparsely populated windy region and the wind blows just when we need electricity the most, i.e. in the autumn and winter. Also, the price of producing electricity from wind or solar power is cheaper since there is no need to buy fuel to produce the electricity. This is also important in conjunction with stock market logic: the more renewable energy there is on the market at a cheaper price, the lower the price of electricity will be for everyone.
For more Wind Turbineinformation, please contact us. We will provide professional answers.
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