Frequently Asked Questions

How does a wind turbine make electricity?

Wind turbines work a bit like a fan in reverse. Most wind turbines 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 large capsule at the top of the tower where all the electrical components are located.

Most wind turbines have three blades which can be orientated so they always face into the wind. On large modern turbines the wind turns the blades around slowly - typically at 10-20 revolutions per minute.

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

The energy pay back time is the time taken to generate the same amount of energy that is used in the manufacture, construction and operation of the wind turbine. The pay back time for the average wind farm in the UK is 5-7 months.

How much of the time are wind turbines producing electricity?

Depending on the wind resource available at a particular site, wind turbines produce electricity for about 80-85% of the year on average. Sometimes the "capacity factor" is talked about: this relates to the energy produced over a year. If a wind turbine has a capacity factor of 30% then it produces 30% of the amount of energy it could have produced if it was working flat out all through the year. The capacity factor is a function of variations in wind speed rather than the efficiency of the wind turbines.

What about effects on bird life?

Ongoing survey work at a number of sites in England and Scotland has not identified any impact on bird populations. The Royal Society for the Protection of Birds (RSPB) supports the development of renewable energy technologies such as wind power because they help mitigate climate change, which it believes "poses the most significant long-term threat to the environment… The available evidence suggests that appropriately positioned wind farms do not pose a significant hazard for birds".

Nuon always undertakes appropriate surveys and consultation before proposing a new wind farm development.

What about the noise wind turbines make?

Modern wind turbines are remarkably quiet, and are specifically designed to keep noise to a minimum. All wind farm noise assessments are undertaken using the methodology developed for the Department of Trade & Industry (DTI) and published in 'The Working Group on Noise from Wind Turbines (1996): Assessment and Rating of Noise from Wind Farms' (ETSU-R-97). Noise levels are considered in the overall planning process for wind farms, and permissible noise levels at nearby dwellings are controlled by strict guidelines to ensure residents are not disturbed.

What about infrasound - low frequency noise affecting health?

Early in 2004 the press highlighted the fact that low frequency noise or 'infrasound' could be produced by wind turbines, and that this was a possible cause of sleep interruption and headaches.

However, 'Low Frequency Noise and Vibrations at a Modern Wind Farm' (ETSU W/13/00392/REP), commissioned by the DTI in 1997, comprehensively assessed the vibrations from wind turbines and concluded that:

• Vibration levels decrease rapidly with distance; 
• There was no clear increase in vibration with wind speed; 
• Levels were 10 times lower than the safety requirements for modern laboratories 100 metres away from the turbine.
• Subsequent studies have shown that levels of infrasound from wind turbines are substantially below the strongest levels known to have any effect on humans or structures.

It should also be noted that there are other sources of infrasound in the modern world - cars and other road traffic, aircraft, trains, factories, combustion, mining and quarrying and compressors and pumps, as well as domestic appliances like fridges, air conditioning and fans, sound systems and television sets. Infrasound also occurs in the natural environment through wind, the sea, storms, etc.

Doesn't the dirty back-up power required when the wind stops blowing mean that the CO2 saving is wiped out?

This rather bizarre claim is increasingly commonly made by anti-wind campaigners.

Their argument is quite simply wrong. The national grid needs back-up regardless of wind power because it is needed for all forms of energy generation to cover unexpected increases in demand (a cold snap in winter, England playing football on television, etc). In fact, one of the biggest back-up requirements on the system these days is because of Sizewell B nuclear power station. When it fails (as it has done recently due to safety concerns) it knocks out a huge amount of capacity in an instant - unlike wind, where any variation is both gentle and predictable. Only when there is a very large capacity of wind on the system (above 10%) will the variability of the wind become noticeable over the normal variation on the system. Only then will any of the required back-up be specifically due to wind power, and only at this point could any carbon emissions from back-up plant be counted against wind power.

In fact, it is widely accepted that only very minor levels of back-up would be needed even if wind were to account for 20% wind of the generating capacity on the grid system. Under current government policies this level of wind power is not likely to be achieved until after 2020. In terms of emissions, even if the back-up was provided by the dirtiest option (coal power), with 10% wind power on the system, only 1% of the CO2 saved by the wind would be emitted from the back-up, and 99% would be saved. Coal, of course, is not the only option for back-up - gas is about half as "dirty", and both hydro-power and biomass are renewable forms of energy that can perform the same function. In the future a wide range of renewable energy technologies would complement one another and offer the chance for completely secure and completely clean energy system, including both primary generation and back-up.

Do wind turbines spoil the landscape?

This is a highly subjective issue. Being visible is not necessarily the same as being intrusive. While some people express concern about the effect wind turbines have on the beauty of our landscape, others see them as elegant and beautiful, or symbols of a better, less polluted future.

The landscape we inhabit is largely human-made and it evolves over time. In comparison to other energy developments like nuclear, coal and gas power stations, or open cast mining, wind farms have relatively little visual impact. Nevertheless sites within Areas of Outstanding Natural Beauty (AONBs) or National Parks are unlikely to be appropriate for large wind farms.

Wind energy is one of the most environmentally benign ways of producing the electricity we need to power our daily lives. If we don't switch to cleaner forms of energy, climate change will severely and irrevocably alter much of our landscape, as well as the animal and plant life it contains.

What happens when the wind stops blowing?

Wind turbines only operate when the wind blows. At the moment, when the wind stops blowing, electricity continues to be provided by other forms of generation. But the UK is the windiest country in Europe, so we have a massive resource waiting to be used. And in the future all our electricity could come from a mix of complementary renewable sources - balancing wind power with wave, tidal, solar and biomass.

There is a lot of confusion about the reliability of different sources of electricity. No power stations are able to operate all the time without stopping. Many so-called reliable sources such as nuclear power stations suffer from unexpected 'outages' when reactors must be shut down, often at short notice, for essential safety maintenance. Unreliability of this kind is far harder to deal with as the amounts of electricity involved are generally much higher. By comparison, the variation in output from wind farms distributed around the country is scarcely noticeable. Another great advantage of wind power is that the available wind resource is much greater during the colder months of the year when energy demand is at its highest.

At present, the national grid can be operated effectively and economically with up to 20% of the electricity capacity being provided by variable energy sources such as wind. At the levels of wind production being considered over the next few decades, such variability can easily be accommodated by the grid system.

Can wind meet all our electricity needs?

At the moment, wind meets less than 1% of the UK's electricity needs, but the UK wind resource is enormous. The DTI calculates that onshore wind could theoretically meet 80% of our current electricity demand, and that the offshore wind resource could supply 10 times our needs.

Yet the UK remains close to the bottom of the league table in comparison with other European countries in terms of the percentage of our electricity consumption met by renewable energy, despite the fact that the UK has the largest renewable resources in Europe. Germany for example has only a quarter of the UK's offshore wind resource, but plans for offshore wind far outstrip the UK's ambitions. Meanwhile, Denmark already generates 20% of its electricity from wind power.

A report in 2002 by AEA Technology for Greenpeace entitled 'Sea Wind East' shows that nuclear power's contribution to our electricity needs (currently around a quarter) could be replaced by 2020 by wind farms off the coast of East Anglia. That's just one renewable technology in one part of the UK.

In actual fact it's unlikely that wind power alone will meet all our electricity needs, but it will be achieved by a balance of renewable sources including wind, wave, solar and biomass.

Do wind farms affect house prices?

There is no evidence to date to show a negative trend in property values amongst properties close to wind farms. According to the Royal Institution of Chartered Surveyors, there are no studies that suggest an effect either way, but at Nympsfield in Gloucestershire house prices continued to gain after plans for the turbine were announced in 1992 and have continued to rise since the turbine began operating in 1997.

Wilcon Homes, who have developed housing close to an operating wind farm - Taff Ely - in south Wales, have no reservations about the effect of the presence of the turbines. According to David Swithenbank, Sales Manager for the development, "The windmills have not affected people wanting to buy homes; they are selling very well and no purchasers have expressed a problem with the turbines."

A recently commissioned poll carried out by Robertson Bell Associates, an independent market research agency and a member of the Association of British Market Research Companies, found that: 

• At Taff Ely Wind Farm, south Wales 70% of respondents say they are able to see the wind farm from their home. "In regards to house prices, more than three in four (78%) say the wind farm has had no effect, with a further 15% saying 'don't know'. As many residents say house prices have increased a little because of the wind farm (3%) as say they have decreased a little (3%), similarly, as many say they have increased a lot (1%) as say decreased a lot (1%)." 
• At Novar Wind Farm in Scotland: "In regards to house prices, almost three in four (72%) say the wind farm has had no effect, with a further 26% saying 'don't know'. None of the respondents say house prices have decreased as a result of the wind farm. Indeed, 1% say house prices have increased a little because of the wind farm".

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

Wind turbines can be sited offshore where the wind blows harder and the available resource is enormous. The UK's first two offshore wind turbines have been installed off Blyth in Northumberland. The UK's first large scale offshore wind farm - North Hoyle, off the North Wales coast - consists of 30 turbines able to meet the electricity needs of around 50,000 homes. Another has been constructed off the East Anglian coast - Scroby Sands, near Great Yarmouth. Similar sized offshore wind farms are currently being developed in 16 other locations around the British coast.

However, the urgent need to respond to climate change means that we will need to use as many renewable resources as we can as quickly as possible, and that means both onshore and offshore wind. At present onshore wind is one of the most economically competitive of the renewable technologies. Due to the technical hurdles of offshore construction and connection to the national grid, the cost of delivered energy from offshore wind farms is estimated to be at least 30% higher than that from equivalent land-based turbines. There are also a number of other constraints on the development of offshore wind resources, including a limited number of suitable locations, new consents procedures, and objections from the Ministry of Defence which are likely to slow progress on some of these sites.

The offshore wind resource is huge - the DTI estimates it could supply current electricity demand 10 times over - and undoubtedly offshore wind will soon play an important role in our electricity mix. However, onshore wind is also essential if the UK renewable energy market is to be successful and if the government's target of 10% of electricity generation from renewable sources by 2010 is to be met.

Furthermore, as many people like the look of wind turbines, it should not be assumed that it would be more desirable to situate all wind turbines far offshore. Onshore wind farms can also be significant generators of revenue for small rural communities, and particularly for farmers looking for diversification. Well placed onshore wind farms can make a significant contribution to reducing and reversing the decline in rural communities which we have seen in the UK over the last 60+ years.

Isn't energy efficiency just as important?

Energy efficiency is essential - it is the other half of the solution to meeting the UK's energy demands. Decreasing electricity demand can deliver immediate benefits both in terms of carbon reductions and energy security. It is also one of the cheapest short term solutions since efficiency in energy use usually also saves on costs.

But however much we improve the way we use energy, we are always going to have to generate electricity, and it is vital that we make more use of energy sources that are safe, clean, secure and renewable. Future predictions for transport indicate that we will become even more reliant on electricity, either as a direct source of power for vehicles or as a means of producing hydrogen for fuel cells.

Both energy efficiency and wind power have important roles to play in a sustainable energy policy of the future and have massive potential to help solve serious local, national and international environmental problems.

For more on energy efficiency see: Energy Saving Trust.

Does wind farming affect tourism?

There is no evidence to suggest that wind farms deter tourists, indeed many wind farms are themselves tourist attractions.

For example, the UK's first commercial wind farm in Cornwall received 350,000 visitors in its first 8 years of operation - an energy centre at the site opened in 2001 and received 50,000 visitors in its first year. In Swaffham, Norfolk, tourists queue to climb the wind turbine tower to the viewing platform at the top.

In Scotland a MORI poll was undertaken in 2002 regarding wind farms in the Argyll area. 80% of tourists said they would be interested in visiting a wind farm if it were open to the public with a visitor centre.

In Denmark many tour agencies run boat trips to take visitors to see the offshore wind farm at Middelgrunden, near Copenhagen.