Wind Turbine FAQ's
The need for a turbine
Wind power is currently the most established form of renewable energy: wind turbines for electricity generation were first installed en masse in the 1980s and there are now more than 3154 wind turbines in operation in the UK (February 2011). Whilst turbine technology is now quite advanced, there are still inherent problems with wind power: what happens when there is no wind? At the moment, the national grid can cope with the fluctuations of output from wind farms because traditional power stations still supply the majority of power, and their output is stable. But as old power stations are decommissioned, and the proportion of electricity supplied to the grid from wind farms increases, the fluctuations in their output become more of a problem.
One of the main aims of the Hydrogen Office project is to address this problem of fluctuating supply, using hydrogen technology to buffer the output from wind generation. A wind turbine is currently under construction on a site nearby, and it will provide electricity and heat to the Hydrogen Office. Over the course of the year the turbine will not only generate sufficient electricity and hydrogen for the heating and lighting requirements of the Hydrogen Office, but it will also generate surplus hydrogen for research and development purposes, as well as generating enough electricity to meet the annual energy demands of a number of other buildings on the Business Park.
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.
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 metres/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 10 - 30 revolutions per minute at constant speed. However, an increasing number of machines operate at variable speed. For more information, see the BWEA information on wind energy technology .
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 25th birthday in May 2005. The Vestas 30kW machine has operated steadily throughout its lifetime, with none of the major components needing to be replaced.
What happens when a wind farm is taken down / decommissioned?
Wind energy technology is essentially reversible, and compared to the problems associated with decommissioning a nuclear power station, or a coal or gas fired plant, decommissioning a wind farm is straightforward and simple.
At the end of its operating life, the ground at the base of the turbine proposed in this project will be returned to the condition it was in prior to its development.
How much of the time do wind turbines produce electricity? / How efficient are wind turbines?
A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs depending on wind speed.
The maximum energy which a wind turbine can extract from the wind is just under 60%, and is known as the Betz limit. However the meaning of efficiency is misleading in this instance, as the wind is free.
People often confuse efficiency with a wind turbine's capacity factor. The capacity factor is simply the wind turbine's actual annual energy output compared to what it theoretically could produce if the wind was strong enough all year round. Over the course of a year, a turbine in the UK will generate about 30% of the theoretical maximum output.
Of course, wind turbines often produce more energy than is needed, for example at night when demand is low, This energy is wasted if not stored, and this is where hydrogen production is most useful, as energy which would otherwise be wasted is stored and used at times when demand exceeds supply.
In order to help deliver the Programme for Government commitment to make an equitable contribution to the UK effort, the Scottish Executive set targets that 80% of electricity generated in Scotland should come from renewable sources by 2020.
Hydrogen storage is an important aspect of this target, and the Forum for Renewable Energy Development in Scotland (FREDS) established the Hydrogen Energy Group (HEG) to examine and report on the potential and opportunities that hydrogen and fuel cell technology represents for Scotland in the short and long term.
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 not 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, as this design has been found to have a greater aesthetic appeal. The disadvantage is that each blade will add to the overall cost and weight and can be more difficult to install, particularly offshore.
Two-bladed machines are cheaper and lighter, with higher a running speed, which reduces the cost of the gearbox, and they are easier to install. However two-bladed machines can be noisier and are not as visually attractive, appearing 'jerky' when they turn. The engineering ideal would be to have only one blade, and some one-bladed early prototypes were developed, but didn't stand the test of time.
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 also competitive with new clean coal fired power stations and cheaper than new nuclear power. The cost of wind energy varies according to many factors. According to the BWEA, a new onshore wind farm in a good location can generate electricity at a cost of 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 the BWEA’s information on the economics of wind energy.
Can turbines be developed within 1.5km of housing?
There are no national guidelines requiring a wind turbine to be located at least 1.5km away from the nearest houses. If this were the case, the two 120.5m high turbines built at the Michelin factory in Dundee would not have been built. The Michelin turbines are 40m taller than the turbine proposed by the Hydrogen Office, but are located closer to the nearest residential properties than the proposed turbine on the Methil Docks Business Park.
The statement recommending at least 1.5 km between a turbine and the nearest houses was mentioned in paragraph 28 (page 8) of the Consultation Draft (July 2006) of the Scottish Planning Policy 6: "As a general rule, the Scottish Ministers would support a separation distance of 1.5 km between the edge of a town or village and large-scale wind farm developments..." and continues: "...so long as policies recognise that specific proposals may still be acceptable within specified distances if sited and designed so as to avoid unacceptable impacts on communities".
The finalised SPP 6, published in March 2007 has revised the guidelines, stating: "this approach is being adopted solely as a mechanism for steering proposals toward broad areas of search and, within this distance, proposals will continue to be judged on a case-by-case basis".
How tall is the wind turbine ?
The turbine has been obtained from Global Wind Power. The hub of the rotor is 55m high, and the blades had a radius of 23.5m, giving a total height of 78.5m. The turbine is clearly visible as it will be situated on the dock, but it is at a lower elevation than the existing lighting towers in the Energy Park and the power station chimney (the chimney on the old power station in Methil is 91m tall).
Why does it need to be so tall?
Wind speed generally increases as you go higher off the ground (up to a point!), and so the height of a turbine is calculated in relation to how much energy must be extracted from the wind to provide the required output of electricity. The diameter of the rotor is calculated using similar principles.
How much carbon dioxide will the wind turbine save?
Some carbon dioxide will be produced whilst the turbine is being manufactured. However, once operational, it will take just 8months to ‘pay back’ those emissions, because the turbine will lead to carbon dioxide savings between 550 tonnes and 774 tonnes (depending on final turbine choice and wind speed) – equivalent to the carbon dioxide produced by 57 local families.
Are wind turbines safe? / How safe is wind energy?
Wind energy is one of the safest energy technologies. There are now 70,000 wind turbines operating worldwide, some of which have been operating for 25 years. Accidents involving these turbines are very rare, and “it is a matter of record that no member of the public has ever been injured during the normal operation of wind turbine” (BWEA 2007).
What about noise?
Wind turbines are not noisy. The evolution of wind farm technology over the past decade has rendered mechanical noise from turbines almost undetectable.
There are two main types of noise produced by wind turbines: aerodynamic noise, which is produced by the blades as they rotate; and mechanical noise, which is produced by the generator. As noise is such an important consideration for wind turbines, all components within modern turbines are designed to minimise noise levels. 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?
Environmental Noise Impact Assessment
Wind turbines are required to meet strict planning guidelines on noise to ensure that they do not adversely impact their residential neighbours. Within the UK, these guidelines are detailed in ETSU-R-97, The Assessment and Rating of Noise from Wind Farms.
Noise is generally expressed as decibels (dB). Here are a few examples of noise levels from a number of common sources:
Source / Activity
Indicative Noise Level dB(A)
|Threshold of pain||140|
|Jet aircraft at 250m||105|
|Pneumatic drill at 250m||95|
|Truck doing 30mph at 100m||65|
|Busy general office||60|
|Car doing 40mph at 100m||55|
|Wind farm at 350m||34-45|
|Rural night-time background||20-40|
|Threshold of hearing||0|
The proposed turbine would be located approximately 350m from the nearest houses.
Acoustic experts Hayes McKenzie draw the following conclusions on infra-sound: “Infra-sound is defined as noise occurring at frequencies below that at which sound is normally audible. Wind turbines have been cited as significant producers of infra-sound. This has, however, been due to the high levels of such noise, as well as audible low frequency thumping noise, occurring on older ‘downwind’ turbines, of which many were installed in the USA prior to the large-scale take-up of wind power production in the UK. Downwind turbines are configured with the blades downwind of the tower such that the blades pass through the wake left in the wind stream by the tower, resulting in a regular audible thump, with infra-sonic components, each time a blade passes the tower. Virtually all modern turbines, including the model proposed for Methil Docks, are of the upwind design – that is, with the blades upwind of the tower, such that this effect is eliminiated”.
Information provided by the World Health Organisation, states: “There is no reliable evidence that infra-sound below the hearing threshold produces physiological or psychological effects.” In summary, WHO state that “infrasound associated with modern wind turbines is not a source which may be injurious to the health of a wind farm neighbour”.
Acoustic experts Hayes McKenzie draw the following conclusions on low-frequency noise: “Noise from modern wind turbines is essentially broadband in nature in that it contains similar amounts of noise energy in all frequency bands from low to high frequency. As distance from a wind farm site increases, the noise level decreases as a result of the spreading out of the sound energy but also due to air absorption, which increases with increasing frequency. This means that, although the energy across the whole frequency range is reduced, higher frequencies are reduced more than lower frequencies, with the effect that as distance from the site increases, the ratio of low to high frequencies also increases. This effect may be observed with road traffic noise or natural sources such as the sea where higher frequency componenets are diminished relative to lower frequency components at long distances. At such distances, however, overall noise is so low that any bias in the frequency spectrum is insignificant. This effect will be completely insignificant for a single wind turbine”. For more information read BWEA's full report on Low Frequency Noise and Wind Turbines .
What work has been undertaken to identify the noise impact on site?
The first requirement for assessing the noise implications from a wind turbine is to assess what the current background noise levels are in the area surrounding the turbine. Part of the independent environmental noise impact assessment undertaken on this project involved collecting noise data from 3 locations in the residential area immediately adjacent to the Methil Docks Business Park. These included Rose Street, Whyterose Terrace, and the nearest property to the turbine on the High Street. Background noise levels were collected for 21 days during June and July 2007.
The background noise data collected was then analysed to quantify the existing noise levels and derive noise limits, as detailed in the national guidelines (ETSU-R-97).
Using the noise data from the proposed turbine, the predicted turbine noise level has been calculated using International Standard ISO 9613, Acoustics – Attenuation of Sound during Propagation Outdoors, and this was then compared with derived noise limits.
What were the findings from the independent noise impact assessment?
The findings from this work indicate that the noise from the turbine within the residential area will meet the appropriate noise limits, although it may be audible at times depending on levels of background noise, and the wind direction.
The predictions were carried out on a ‘worst case’ basis. This means that the prediction is made for downwind conditions that only occur for certain periods of the year.
What is shadow flicker?
Shadow flicker occurs under certain conditions where, on a sunny day, the sun passes behind the moving blades of a turbine, creating a moving shadow on the ground.
What do the guidelines say about shadow flicker?
Shadow flicker does not cause an issue when experienced outdoors, but may be an issue if experienced through a window. The Scottish Government’s Planning Advice Note (PAN) 45 states “It occurs only within buildings where the flicker appears through a narrow window opening.” Where shadow flicker is found to be a problem in neighbouring properties, there are a number of recognised ways to prevent it.
How far from the turbine could shadow flicker be an issue?
As you get further from the turbine, the potential for shadow flicker reduces. The Department for Trade and Industry advises that, at and beyond a distance of ten times the diameter of the turbine rotor (470m for the size of our propsed turbine), a person should not be able to perceive a turbine chopping through sunlight, but rather as an object with the sun behind it”.
Will I be affected?
As the sun’s position in the sky can be accurately forecast throughout the year, it is possible to calculate exactly when shadow flicker might be an issue.
The project has commissioned an independent assessment of shadow flicker. The model calculates the absolute worst-case scenario, as it assumes there is never any cloud cover, the turbine is always turning, and there are no obstructions that would naturally block the sun. The actual figure is likely to be considerably less than this.
What time of day and year will I be affected?
A computer programme can accurately calculate when shadow flicker may be an issue. The actual times will vary depending on where the house is located in respect to the turbine, though generally it will be limited to the winter months.
What if I am affected by shadow flicker?
If shadow flicker is found to be a nuisance in your home there are a number of simple measures to prevent it. In the first instance, the Hydrogen Office project would look to resolve the issue through the provision of special blinds to affected houses. If this fails to resolve the issue, the turbine will be programmed to turn off on those days of the year where the position and strength of the sun combine to cause a shadow flicker nuisance.
If you have an issue with Shadow Flicker, please click here
Will television reception be affected?
There may be very minor issues with reception for some properties nearest the turbine, where this is found to be the case an adjustment to the aerial normally resolves the problem.
Will the wind turbine lower the value of my property?
There is much debate on this subject, and numerous studies have been undertaken.
One of the largest studies of its kind ever undertaken was in the USA, where over a period of 6 years, 24,300 property sales from 10 locations were analysed. The findings from this work indicated that there was no evidence to suggest that a wind turbine sited within a 5 mile radius of property had a negative impact on property value.
A study into house prices in East Lothian has indicated that property prices in Dunbar have continued to rise above the regional average despite the development of the nearby Crystal Rig wind farm.
An important consideration for this project which differentiates it from other wind farm projects is the link between the proposed wind turbine, and the bigger regeneration project that it forms a core part of. By being part of a project which will raise the profile of the Fife Energy Park, and provide world leading research and development facilities and modern office accommodation, the project is working to attract jobs to the area. Ultimately, investment and jobs in Methil have to be good for the property values of Methil.
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 (BWEA 2007).
The proposed turbine may attract tourists to Methil!
How many wind farms/turbines are there in the UK?
There are around 282 wind farms, comprising 3149 turbines…though the figure is always increasing! For the most recent information, see the BWEA’s list of all the operational wind farms in the UK: it also provides total industry statistics, including the number of wind farms and turbines, total capacity installed, and greenhouse gas emission reductions.