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There are currently some 1,769 wind turbines at 137 sites in the UK. Of these, 5 of the sites are offshore (British Wind Energy Association - 1.3.2007).
Most wind farms are in Cornwall, Cumbria, Wales, Yorkshire, Northern Ireland and Scotland.
Large, modern wind turbines have rotors up to 65 metres in diameter. The towers themselves are between 25 to 80 metres high. This means that the largest turbines can be over 100 metres high from ground to rotor blade tip.
To convert the rated capacity of a turbine (measured in megawatt hours) into usable power, e.g. kilowatt hours per year, do the following calculation:
Rating of turbine (e.g. 2 megawatts) x 24 (hours in the day) x 365 (days in year) x 0.30 (the capacity factor*) x 1,000 (to convert the answer into kilowatt hours, rather than megawatt hours). This gives the kilowatt hours produced per year per turbine. To work out how many households each turbine can provide electricity for, divide this total by 4,400 (the average kilowatt hours used per household per year).
* 0.30 (or 30 per cent) is the average capacity of the turbine, as it does not produce power at 100 per cent all the time, due to factors such as changes in wind conditions, downtime for maintenance. The average value for an onshore turbine in the UK is very roughly 0.3 but this varies from place to place. Offshore turbines tend to operate at a higher capacity of 0.35+ because of stronger and more consistent winds offshore.
A wind turbine can extract 60 per cent of the wind’s energy at most.
It is easy to confuse intermittency with efficiency. Wind farms are highly efficient at turning a free fuel source into electricity. However, the wind does not blow all the time, which is why the average capacity is around 30–40 per cent.
Collectively wind farms can make a huge difference. The DTI calculates that onshore wind could supply up to 100 per cent of our current electricity demand, and that offshore wind could generate ten times this amount. Once other factors such as land availability are taken into account, a more realistic potential is around 40 per cent of current electricity generation, using both onshore and offshore wind turbines.
Wind turbines start operating at wind speeds of four to five metres a second (around 10 miles an hour). They reach maximum power output at around 15 metres a second (around 33 miles an hour). At very high speeds, i.e. gale force winds (25 metres a second or 50+ miles an hour), controls help to prevent damage to the turbine. Some wind turbines, particularly those used in buildings and urban environments, are designed to start producing energy at lower wind speeds.
At very high wind speeds, i.e. gale force winds (25 metres a second or 50+ miles an hour), controls kick in to prevent damage to the turbine.
When there’s no wind, no electricity is generated. So there are technical challenges to including this intermittent form of generation into the electricity network. On a small scale this is less of an issue as storage devices, such as batteries, can be used. However, as there are wind farms all over the UK, the changes in power from individual turbines will be smoothed out, because, if the wind drops in one area, it is still highly likely to be blowing in others.
The electricity grid always needs some form of back-up power (usually coal or gas) in case of sudden power stoppages at any power station. The National Grid Company has estimated that only a little extra back-up is needed to cope with wind power generating more energy. Intermittent energy sources such as wind energy could meet up to 10 per cent of the country’s needs, without significant changes to the system’s operation.
Thanks to advances in wind turbine technology, well-designed and well-positioned turbines can be quiet enough not to disturb people living just a few hundred metres away. At these distances, the natural noise of the wind usually drowns any noise they do make. It is perfectly possible to stand beside a wind turbine and have a conversation without raising your voice. However, proposals to install wind turbines need to meet strict noise standards to protect nearby residents from any undue disturbance.
People visiting wind farms are often surprised at how quiet they actually are. The Scottish Executive’s public opinion survey is one of many showing that concerns about noise are often unfounded. A survey conducted before Scottish wind farms were built found that 12 per cent of people living near the potential sites thought that the turbines would be noisy. However, once they had experience of the wind farm operating, only 1 per cent felt this was true.
The main sound that can be heard if you are close to the turbines is the swishing of the blades through the air. As a comparison, a wind farm 350 metres away produces 35–45 decibels. A car travelling 100 metres away at 40mph generates 55 decibels. Background noise in the countryside at night is 20–40 decibels.
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A typical farm of 20 turbines covers an area of one to two square kilometres. However, as the turbines take up only 1 or 2 per cent of this land the rest can still be used for agriculture.
Wind farming is popular with farmers, because they can continue to use their land for growing crops or even grazing livestock, as sheep, cows and horses are not disturbed by the turbines.
There is no evidence to suggest that wind farms deter tourists. In fact, many wind farms are actually tourist attractions.
For example, 350,000 people visited the UK’s first commercial wind farm in Delabole, Cornwall in its first eight years. The Gaia energy centre opened at the site in 2001 and received 50,000 visitors in its first year. In Swaffham, Norfolk, tourists queue to climb the wind turbine tower to get to the viewing platform at the top.
In Scotland, a MORI poll in 2002 found that 80 per cent of tourists said they would be interested in visiting a wind farm in Argyll if it were open to the public and had a visitor centre.
Public attitudes have been widely surveyed and consistently show that a clear majority favour wind energy. In a recent survey for the British Wind Energy Association’s 2004 ‘Embrace the revolution’ campaign, 74 per cent agreed that wind farms were necessary so that the UK could produce renewable energy to help it meet current and future energy needs. People living near wind farms reflected this positive feeling. In the same survey, 59 per cent did not believe wind farms spoiled the scenery or caused noise nuisance. In many cases, people who viewed wind farms negatively before they were built changed their minds afterwards.
These positive attitudes are backed up by a 2003 DTI survey, where over 90 per cent of those surveyed agreed that ‘the Government should encourage the use of renewable energy’. When asked if they would approve of a wind farm being developed in their area, more than 67 per cent said yes. For people who already lived within 5 kilometres of a wind farm this figure increased to over 80 per cent.
A Scottish Executive public opinion survey also found that concerns about noise are often unfounded. A survey conducted before Scottish wind farms were built found that 12 per cent of people living near the potential sites thought that the turbines would be noisy. However, once they had experience of the wind farm operating, only 1 per cent felt this was true.
Also, research by the Royal Society for the Protection of Birds (source: BRMB/RSPB, October 2001) revealed that:
No matter how much we improve how we use energy, we will always have to generate it. It is vital that we make more use of safe, clean, secure and renewable energy sources.
Both energy efficiency and wind power are important to a future sustainable energy policy. They have the potential to help massively in solving serious local, national and international environmental problems.
Wind farms can occasionally affect TV and radio signals. However, suitable repeater equipment or TV aerial modifications can easily solve any problems found during the planning process.
Since 1998 – when the energy market was opened up to competition – you can switch to a ‘green’ supplier. There are generally two main types of ‘green’ electricity tariffs (some schemes provide a combination of both):
From 1 July 2004, new legislation requires individual electricity supply companies to disclose how much each energy source contributed to the overall fuel mix of the supplier the previous year. The first year’s data will, therefore, be available in 2005.
The structures that support wind turbines are designed to encourage swell to roll over them. This stops waves from damaging the turbines by crashing over them. According to ‘Surfers Against Sewage’, the farms may actually benefit surfers by reducing onshore winds a little and their potential to disturb the surf closer to the shore.