Show all / Hide all

What is the wind?

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.

Category: FAQ topic 1

How can you measure the wind?

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.

Category: FAQ topic 1

What is a wind turbine?

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!

Category: FAQ topic 1

How big is a wind turbine?

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 1985, wind turbines were under 1 MW with rotor diameters of around 15 metres.
In 2012, 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.

Category: FAQ topic 1

What is a wind turbine made of?

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.

Category: FAQ topic 1

How is a wind farm designed?

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.

Category: FAQ topic 1

How long does it take to build a wind farm?

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.

Category: FAQ topic 1

What are the costs of building a wind farm?

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.

Category: FAQ topic 1

How efficient are wind turbines?

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.

Category: FAQ topic 1

Why do some wind turbines have two and others three blades?

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.

Category: FAQ topic 1

Why do some of the turbines in a wind farm sometimes stand still?

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.

Category: FAQ topic 1

How much space does a wind farm need?

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.

Category: FAQ topic 1

Could I put a turbine in my garden or on the roof of my house?

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.

Category: FAQ topic 1

Who makes wind turbines?

Browse through our Members Directory to see a comprehensive list of wind turbine manufacturers.

Category: FAQ topic 1

Why don't we put all wind turbines out to sea?

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.

Category: FAQ topic 1

How many wind turbines are there in the EU?

In 2010, 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….

Category: FAQ topic 1

How long does a wind turbine work for?

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.

Category: FAQ topic 1

How fast do the blades turn?

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.

Category: FAQ topic 1

Show all / Hide all

What is the wind?

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.

Category: FAQ topic 1

How can you measure the wind?

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.

Category: FAQ topic 1

What is a wind turbine?

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!

Category: FAQ topic 1

How big is a wind turbine?

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 1985, wind turbines were under 1 MW with rotor diameters of around 15 metres.
In 2012, 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.

Category: FAQ topic 1

What is a wind turbine made of?

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.

Category: FAQ topic 1

How is a wind farm designed?

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.

Category: FAQ topic 1

How long does it take to build a wind farm?

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.

Category: FAQ topic 1

What are the costs of building a wind farm?

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.

Category: FAQ topic 1

How efficient are wind turbines?

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.

Category: FAQ topic 1

Why do some wind turbines have two and others three blades?

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.

Category: FAQ topic 1

Why do some of the turbines in a wind farm sometimes stand still?

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.

Category: FAQ topic 1

How much space does a wind farm need?

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.

Category: FAQ topic 1

Could I put a turbine in my garden or on the roof of my house?

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.

Category: FAQ topic 1

Who makes wind turbines?

Browse through our Members Directory to see a comprehensive list of wind turbine manufacturers.

Category: FAQ topic 1

Why don't we put all wind turbines out to sea?

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.

Category: FAQ topic 1

How many wind turbines are there in the EU?

In 2010, 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….

Category: FAQ topic 1

How long does a wind turbine work for?

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.

Category: FAQ topic 1

How fast do the blades turn?

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.

Category: FAQ topic 1

Show all / Hide all

What is the wind?

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.

Category: FAQ topic 1

How can you measure the wind?

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.

Category: FAQ topic 1

What is a wind turbine?

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!

Category: FAQ topic 1

How big is a wind turbine?

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 1985, wind turbines were under 1 MW with rotor diameters of around 15 metres.
In 2012, 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.

Category: FAQ topic 1

What is a wind turbine made of?

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.

Category: FAQ topic 1

How is a wind farm designed?

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.

Category: FAQ topic 1

How long does it take to build a wind farm?

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.

Category: FAQ topic 1

What are the costs of building a wind farm?

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.

Category: FAQ topic 1

How efficient are wind turbines?

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.

Category: FAQ topic 1

Why do some wind turbines have two and others three blades?

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.

Category: FAQ topic 1

Why do some of the turbines in a wind farm sometimes stand still?

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.

Category: FAQ topic 1

How much space does a wind farm need?

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.

Category: FAQ topic 1

Could I put a turbine in my garden or on the roof of my house?

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.

Category: FAQ topic 1

Who makes wind turbines?

Browse through our Members Directory to see a comprehensive list of wind turbine manufacturers.

Category: FAQ topic 1

Why don't we put all wind turbines out to sea?

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.

Category: FAQ topic 1

How many wind turbines are there in the EU?

In 2010, 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….

Category: FAQ topic 1

How long does a wind turbine work for?

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.

Category: FAQ topic 1

How fast do the blades turn?

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.

Category: FAQ topic 1

Show all / Hide all

What is the wind?

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.

Category: FAQ topic 1

How can you measure the wind?

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.

Category: FAQ topic 1

What is a wind turbine?

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!

Category: FAQ topic 1

How big is a wind turbine?

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 1985, wind turbines were under 1 MW with rotor diameters of around 15 metres.
In 2012, 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.

Category: FAQ topic 1

What is a wind turbine made of?

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.

Category: FAQ topic 1

How is a wind farm designed?

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.

Category: FAQ topic 1

How long does it take to build a wind farm?

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.

Category: FAQ topic 1

What are the costs of building a wind farm?

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.

Category: FAQ topic 1

How efficient are wind turbines?

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.

Category: FAQ topic 1

Why do some wind turbines have two and others three blades?

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.

Category: FAQ topic 1

Why do some of the turbines in a wind farm sometimes stand still?

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.

Category: FAQ topic 1

How much space does a wind farm need?

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.

Category: FAQ topic 1

Could I put a turbine in my garden or on the roof of my house?

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.

Category: FAQ topic 1

Who makes wind turbines?

Browse through our Members Directory to see a comprehensive list of wind turbine manufacturers.

Category: FAQ topic 1

Why don't we put all wind turbines out to sea?

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.

Category: FAQ topic 1

How many wind turbines are there in the EU?

In 2010, 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….

Category: FAQ topic 1

How long does a wind turbine work for?

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.

Category: FAQ topic 1

How fast do the blades turn?

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.

Category: FAQ topic 1