EnergyInsights.net 
39: Wind Energy - helpful resources and FAQs 03-06-2006 12:42 am

BWEA.com

 

Frequently Asked Questions:

Wind energy and environmental impact

Are wind turbines noisy?
Do wind turbines produce low frequency noise?
Why don't they make turbines that look like old fashioned windmills?
Why don't we put all the wind turbines out to sea?
Do wind turbines frighten livestock?
How long does it take for a turbine to 'pay back' the electricity used to manufacture it?

Statistics and data

How many wind farms/turbines are there in the UK?
How much electricity does one wind turbine produce?

Public opinion

How popular is wind energy?
Does wind farming affect tourism?
How safe is wind energy?
What can I do to help wind energy?
I want to visit a wind farm, where is the nearest one to me?

The mechanics and workings of wind turbines

What are wind turbines made of ?
How big are they?
How does a wind turbine make electricity?
How strong does the wind have to blow for the wind turbines to work?
How fast do the blades turn?
How much space do wind turbines require?
What happens when the wind stops blowing?
How long do wind turbines last?
What happens when a wind farm is taken down/decommissioned?
How efficient are wind turbines?
Why don't wind turbines have lots of blades?
Why do some wind turbines have two whilst others have three blades?

Wind energy economics

How much does it cost to make electricity from the wind?
How much of the time do wind turbines produce electricity?

Can I have my own wind turbine

Could I put a turbine in my garden or on the roof of my house?
I want to build my own wind turbine
Isn't it cheaper to save electricity?
Is there funding available to help me set up a wind turbine?

Are wind turbines noisy?

Wind turbines are not noisy. The evolution of wind farm technology over the past decade has rendered mechanical noise from turbines almost undetectable with the main sound being the aerodynamic swoosh of the blades passing the tower. There are strict guidelines on wind turbines and noise emissions to ensure the protection of residential amenity. It is possible to stand underneath a turbine and hold a conversation without having to raise your voice. As wind speed rises, the noise of the wind masks the noise made by wind turbines. For more information, read the facts about noise from wind turbines or why not visit a wind farm and experience it for yourself.

Click here to download The Assessment and Rating of Noise from Wind Farms, produced by ETSU for the DTI

Do wind turbines produce low frequency noise?

There is always low frequency noise present in any ambient quiet background and it can be produced by a variety of sources, including machinery, transport and natural sources such as the sea, wind and thunder. It has been repeatedly shown by measurements of wind turbine noise undertaken in the UK, Denmark, Germany and the USA over the past decade, and accepted by experienced noise professionals, that the levels of low frequency noise and vibration radiated from modern, upwind configuration wind turbines are at a very low level; so low that they lie below the threshold of perception.

Read BWEA's full report on Low Frequency Noise and Wind Turbines.

Why don't they make turbines that look like old fashioned windmills?

The old fashioned windmill is viewed with nostalgia, and some people prefer the look of them to that of their modern counterparts. Just because wind turbines are modern, it doesn't mean they won't look just as good over time.

A modern wind turbine is simply an improved windmill. Every aspect of their design has been optimised, making them far more efficient than old style windmills at generating electricity. To make them look more old-fashioned would just result in more expensive electricity.

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

We will need a mix of both onshore and offshore wind energy to meet the UK's challenging targets on climate change. At present, onshore wind is more economical than development offshore. Furthermore, offshore wind farms will 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 missing our renewable energy targets and commitment to tackle climate change.

Here in the UK, we are lucky enough to have good winds both on and offshore, and our first offshore turbines at Blyth began generating electricity in December 2000. More offshore wind farms are now under construction and the first of the large-scale developments, North Hoyle, was operational at the end of 2003. Visit our Offshore section for more information, including an introduction to offshore wind energy, a list of offshore wind farms around the world, and of course, Blyth Offshore, the UK's first offshore wind farm.

Do wind turbines frighten livestock?

Wind farming is popular with farmers, because their land can continue to be used for growing crops or grazing livestock. Sheep, cows and horses are not disturbed by wind turbines.

The first wind farm built in the UK, Delabole, has a stud farm and riding school, and the farmer, Peter Edwards, often rides around the wind farm on his horse.

How long does it take for a turbine to 'pay back' the energy used to manufacture it?

The comparison of energy used in manufacture with the energy produced by a power station is known as the 'energy balance'. It can be expressed in terms of energy 'pay back' time, i.e. as the time needed to generate the equivalent amount of energy used in manufacturing the wind turbine or power station.

The average wind farm in the UK will pay back the energy used in its manufacture within six to eight months, this compares favourably with coal or nuclear power stations, which take about six months.

How popular is wind energy?

Wind energy is one of the most popular energy technologies. Opinion surveys regularly show that just over eight out of ten people are in favour of wind energy, and less than one in ten (around 5%) are against it. The rest are undecided. For more information, read about public attitude surveys in wind energy.

How safe is wind energy?

Wind energy is one of the safest energy technologies. No member of the public has ever been injured by wind energy or wind turbines anywhere in the world, despite the fact that there are now over 68,000 operational wind turbines.

Does wind farming affect tourism?

There is no evidence to suggest this. The UK's first commercial wind farm at Delabole received 350,000 visitors in its first ten years of operation. A MORI poll in Scotland showed that 80% of tourists would be interested in visiting a wind farm. Furthermore, wind farm developers are often asked to provide a visitor centre, viewing platforms and rights of way to their sites.

]What can I do to help wind energy?

One of the most helpful things you can do is to help win the debate on wind energy. Respond to letters in local and national papers, participate in radio phone-in programmes and wherever else the opportunity arises. Don't be one of the silent majority. To find out more about projects in your area, visit Yes2Wind.

From 1998 you have been able to choose who supplies your electricity. 'Green' electricity is available from most electricity suppliers, in line with the new Government obligation on electricity companies to source 10% of their supply from renewable energy. Find out more.

You can consider having your own wind turbine, for more information click here.

I want to visit a wind farm, where is the nearest one to me?

Have a look at our interactive map of UK wind farms. You can find which wind farm is closest to you, see details about the project and pictures!

What are wind turbines made of?

The towers are mostly tubular and made of steel, generally painted light grey. Some towers are made of concrete. The blades are made of glass-fibre reinforced polyester or wood-epoxy. They are light grey because this is the colour which is most inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.

How big are they?

Large modern wind turbines have rotor diameters ranging up to 65 meters while smaller machines (around 30 meters) are typical in developing countries. Towers range from 25 to 80 meters in height. For more information, see the BWEA factsheet on wind energy technology. Information about specific wind farms is available on our interactive map of UK wind.

How does a wind turbine make electricity?

The simplest way to think about this is to imagine that a wind turbine works in exactly the opposite way to a fan. Instead of using electricity to make wind, like a fan, turbines use the wind to make electricity.

Almost all wind turbines producing electricity consist of rotor blades which rotate around a horizontal hub. The hub is connected to a gearbox and generator, which are located inside the nacelle. The nacelle is the large part at the top of the tower where all the electrical components are located.

Most wind turbines have three blades which face into the wind; the wind turns the blades round, this spins the shaft, which connects to a generator and this is where the electricity is made. A generator is a machine that produces electrical energy from mechanical energy, as opposed to an electric motor which does the opposite! You can see an animation of this here.

How strong does the wind have to blow for the wind turbines to work?

Wind turbines start operating at wind speeds of 4 to 5 metres per second (around 10 miles an hour) and reach maximum power output at around 15 meters/second (around 33 miles per hour). At very high wind speeds, i.e. gale force winds, (25 metres/second, 50+ miles/hour) wind turbines shut down. For more information, see the BWEA factsheet on wind energy technology.

How fast do the blades turn?

The blades rotate at anything between 50-15 revolutions per minute at constant speed. However, an increasing number of machines operate at variable speed. For more information, see the BWEA factsheet on wind energy technology.

How much space do wind turbines require?

The wind is a diffuse form of energy, in common with many renewable sources. A typical wind farm of 20 turbines might extend over an area of 1 square kilometre, but only 1% of the land area would be taken out of use, the remainder can be used for other purposes, such as farming or as natural habitat.

To obtain 10% of our electricity from the wind would require constructing around 12,000 MW of wind energy capacity. Depending on the size of the turbines, they would extend over 80,000 to 120,000 hectares (0.3% to 0.5% of the UK land area). Less than 1% of this (800 to 1,200 hectares) would be used for foundations and access roads, the other 99% could still b used for productive farming. For comparison, between 288,000 to 360,000 hectares (1.2-1.5% of the UK land area) is covered by roads and some 18.5 million hectares (77%) are used for agriculture.

What happens when the wind stops blowing?

When the wind stops blowing, electricity continues to be provided by other forms of generation, such as gas etc. Our electricity system is mostly made up of large power stations, and the system has to be able to cope if one of these large plants goes out of action. It is possible to have up to 10% of the country's needs met by intermittent energy sources such as wind energy, without having to make any significant changes to the way the system operates. More can be accommodated, but extra storage capacity or spinning reserve would be necessary, which would have a cost implication. For more information, see our factsheet or read Can we rely on the wind?

See also our Briefing Sheet on Wind Power and Intermittency.

How long do wind turbines last?

A wind turbine typically lasts around 20-25 years. During this time, as with a car, some parts may need replacing.

The very first of the mass-produced turbines celebrated its 20th birthday in May 2000. The Vestas 30kW machine has operated steadily throughout its lifetime, and so far, none of the major components have had to be replaced.

What happens when a wind farm is taken down/decommissioned?

The way that a planning authority wishes to have a wind farm decommissioned should be covered by clauses in its planning permission. These clauses typically require all visible traces of the wind farm to be removed. This takes care of the turbines. Service tracks, if there are any, could be removed, although it may be best to leave them. Obviously each case is different, depending upon the size and geography of the development. Developers will then comply with these clauses.

The concrete bases could be removed, but it may be better to leave them under the ground, as this causes less disturbance. If so, they would be covered with peat, stone or other indigenous material, and the site returned as closely as practicable to its original state.

Compared to the problems associated with decommissioning a nuclear power station, or a coal or gas fired plant, decommissioning a wind farm is straight forward and easy!

How efficient are wind turbines?

The theoretical maximum energy which a wind turbine can extract from the wind impinging upon it, is around 60%. However the meaning of efficiency is different with wind energy, where the fuel is free. The primary concern is not the efficiency for its own sake, but to improve productivity in order to bring the price of wind energy down.

People often confuse efficiency with intermittency, for more information see our factsheet on intermittency.

Why don't wind turbines have lots of blades?

People often wonder why there aren't more blades on wind turbines. 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 no need much torque or turning force. These machines generally have three or two blades. On the other hand, wind pumps operate with plenty of torque but not much speed and therefore have many blades.

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

The majority of modern wind turbines have three blades. The advantages of three bladed turbines are greater energy output, and greater aesthetic appeal. The disadvantages are that they cost and weigh more and can be more difficult to install.

Two bladed machines are cheaper and lighter. They have higher running speeds, which reduces the cost of the gearbox and they are easier to install. However two bladed machines can be noisier and appear 'jerky' when they turn.

How much does it cost to make electricity from the wind?

Wind energy is one of the cheapest of the renewable energy technologies. It is competitive with new clean coal fired power stations and cheaper than new nuclear power. The cost of wind energy varies according to many factors. An average for a new onshore wind farm in a good location is 3-4 pence per unit, competitive with new coal (2.5-4.5p) and cheaper than new nuclear (4-7p). Electricity from smaller wind farms can be more expensive. For more information see our factsheet on Wind Energy and the UK's 10% Target.

How much of the time do wind turbines produce electricity?

A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs dependent on wind speed. Over the course of a year, it will generate about 30% of the theoretical maximum output. This is known as its load factor. The load factor of conventional power stations is on average 50%.

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. For more information on small scale wind energy, see our factsheet I want my own turbine and for advice about the best place to site a turbine, see our factsheet, siting a wind turbine.

I want to build my own wind turbine

There is a very good book on this subject, 'Wind Power Workshop' by Hugh Piggott, available from the Centre for Alternative Technology. For a brief idea of what is involved see how to build your own wind turbine.

Isn't it cheaper to save electricity?

It is cheaper to save electricity than to generate it, by whatever method. The latest information on how much it costs to save electricity is available from the Energy Savings Trust. In their Energy Efficiency Standards of Performance Review, they cited the cost of energy efficiency measures as costing around 1.3 pence per kilowatt hour (per unit). The cost of wind energy is currently around 2.4 pence per unit. However, to combat climate change, the UK will need a mix of both renewable energy technologies and energy efficiency measures.

How many wind farms/turbines are there in the UK?

We have a list of the operational wind farms in the UK, which will also tell you how much electricity they produce.

How much electricity does one wind turbine produce?

One 1.8 MW wind turbine at a reasonable site would produce over 4,7 million units of electricity each year, enough to meet the annual needs of over 1,000 households, or to run a computer for over 1,620 years. 

 

 

 

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