Simple answers to complex problems have always held a fascination for Governments, sometimes with disastrous consequences, and some people see wind power as a simple answer to the complex problem of energy security. Unfortunately the case for wind farms does not stand up to close scrutiny and, far from producing ‘free, unlimited and environmentally friendly’ electricity, they are anything but friendly to the environment of those in whose immediate vicinity these overwhelming structures are erected.
In this paper Cllr. Barnard considers the modern fascination with wind power and the effects it can have on communities and the wider environment.
Wind turbines only produce electricity when the wind speed falls within certain parameters. Too little wind and the blades do not turn, too much and they must be shut down to protect the mechanism. In either case the power they are not producing must be supplied from the grid and this means that reserve capacity need be maintained at fossil fuel or nuclear stations. The Drax power station has an output of 4,000MW and would require 1,600 2.5MW turbines running continuously at rated output to generate an equivalent power but as they cannot run all the time no power station can be shut down. Far from being ‘free’ we end up paying twice – once for the turbine and again for the reserve power in the grid!
To make matters worse, with power companies compelled to pay a premium for electricity from ‘renewable’ sources, wind turbines actually increase our bills! The Renewables Obligation Order was introduced in 2002 and this compels electricity suppliers to obtain an increasing amount of their supplies from ‘renewable’ sources. Any who fail to meet their targets must pay into a fund the proceeds of which are then paid to those suppliers who have achieved targets set by the Government1. A pointless money-go-round which does nothing to benefit the end user.
Turbines are anything but friendly to those unfortunate enough to live in the immediate vicinity who suffer from their impact on the local environment. Shadow flicker when sunlight reflects off the blades and strobing when the rising or setting sun passes behind the blades a hazard to road users and migraine or epilepsy sufferers. Low frequency noise and infra-sound. Interference with TV reception caused either by the magnetic field or by the signal being chopped when the blades are in line of sight between the transmitter and receiver. Ice fling when a build up of ice breaks free under the centrifugal force of the rotating blades and flies off in any direction or when a blade itself shatters and fragments shoot off at up to 200 miles per hour. Harm to wildlife especially migratory birds and bats whose navigation systems are disrupted by the blades and the low frequency noise they produce. Furthermore, with wind farms usually sited in rural communities, considerable disruption can be caused during construction with large components and tens of thousands of tons of material being transported along an inadequate road network.
Wind Turbine Design
Wind turbines can be separated into two types based on the axis about which the turbine rotates. Turbines that rotate around a horizontal axis are more common. Vertical-axis turbines are less frequently used. The vast majority of turbines in operation in the UK or proposed are of the horizontal axis design and the risk factors summarised below relate specifically to this type.
The following is a summary of the risks associated with industrial scale wind turbines, compiled to assist readers to understand the problems and to stimulate further research. It is by no means exhaustive.
In the event of structural failure sections of a turbine blade can be thrown off in much the same way as a stone from a slingshot and at very high speed. For example a rotor of 295 feet diameter turning at 20 revolutions per minute will have a blade tip speed of 309 feet per second or 211 miles per hour.
The distance which a broken blade section might be thrown is a function of the angle of ejection, the length of the blade, the height of the rotor, the speed of rotation and the gravitational constant. For a turbine with a blade tip height of 330 feet this can be up to 1,100 yards dependent on the angle of ejection2.
Such a projectile will impact with the ground then ricochet at something like 150mph with debris being scattered over a distance of up to 330 yards2.
The blade of a turbine is similar to the wing of an aeroplane and the aerodynamic characteristics of a broken blade may well cause it to travel further than would a solid projectile. In order to appreciate the forces to which a turbine is subjected it can be compared to an aircraft; in fact some of the most powerful turbines are comparable to an Airbus A380 in terms of wingspan and mass.
Icing and Ice-Fling
Known to aviators for almost a century, icing occurs on the blades of a turbine in the same way as on the wings of an aeroplane. In winter when the air is moist and the temperature low the leading edges of a wing or turbine blade ice up leading to the formation of icicles of 10 to 20lbs in weight2.
Icicles breaking loose from rotating blades will shoot off in much the same way as a broken blade and a build up of ice will disturb the balance of the rotor placing stresses on the motor, bearing and the structure itself.
Some wind farm operators in Europe think it necessary to establish exclusion zones around their installations warning of the dangers of ice3.
Television and Radar
Television and radar operate on a very similar principle, in fact the inventor of television, John Logie Baird, had also experimented with early radar systems and worked on these during World War II.Â
Terrestrial television signals can suffer interference from wind turbines either as a result of the electromagnetic field or when the rotating blades are in line of sight between transmitter and receiver and the signal is chopped. Similar in effect to the use of chaff or window, strips of aluminium foil dropped from aircraft to confuse radar signals. Other forms of interference, such as ˜ghosting’ can occur when two signals reach the receiver one directly from the transmitter and another bounced off nearby turbines.
A scheme to build eleven turbines off the Holderness coast has been opposed by the Ministry of Defence on the grounds that they could hinder the air defence radar at RAF Staxton Wold4. In France the Ministere de la Defense prohibits wind farms within 30km, (19 miles), of air defence radars5. The Federal Aviation Authority in the United States adopts a similar stance6
Strobing and Shadow Flicker.
Strobing occurs when the sun appears to rise or set directly behind the blades and given the axial tilt of the earth this effect will be visible from locations along a wide arc around the east and west dependent upon the time of year. A hazard to road users and to anyone who is unfortunate to suffer from epilepsy or migraine attacks.
Shadow flicker can occur at any time when sunlight reflects off the rotating blades and poses similar risks to strobing.
Some horse owners report that their animals become disturbed in the presence of turbines and this is acknowledged by the British Horse Society7.
Research sponsored in part by the American Wind Energy Association discovered a significant correlation between bat fatalities and the presence of wind turbines. Studies were conducted at the Mountaineer and Meyersdale Wind Energy Centers located along the Appalachian plateau inWest VirginiaandPennsylvania, respectively. The Mountaineer site has 44 and the Meyersdale site has 20 NEG Micon 1.5 MW turbines. Thermal images indicated that bats are attracted to and investigate both moving and non-moving blades.
Images of bats attempting to land or actually landing on stationary blades and turbine masts suggest possible curiosity about potential roosts or use for gleaning insects. Images of bats chasing turbine blades rotating at slow speeds suggest possible attraction to movement that may be confused with prey or perhaps other bats. Of the 64 turbines studied, one, (turbine 11 at Mountaineer), was non-operational throughout the study period and this was the only turbine where no fatalities were found8.
Audible sound is characterized as a periodic vibration whose frequency can be heard by the average human. While the range of frequencies that any individual can hear is largely related to environmental factors, the generally accepted standard range of audible frequencies is 20 to 20,000 Hz. Frequencies below 20 Hz can usually be felt rather than heard, assuming the amplitude of the vibration is high enough. Higher frequencies outside the human range may be heard by animals such as dogs or bats. The intensity of sound is measured in decibels (dB) and the frequency in Hertz (Hz) or cycles per second.
Wind turbines produce two types of noise, mechanical and aerodynamic. The former originates in the gearing and generator at the top of the mast whilst the latter is caused by the flow of air around the blades and mast and each time a blade passes the mast it emits a characteristic thump. The propagation of sound is affected by many factors such as the topography, air temperature and even the time of day9. At night the sound carries further than during the day10.
The deleterious effects of wind farms was recognised in evidence to the Welsh Affairs Select Committee. “For existing wind farms we are satisfied that there are cases of individuals being subject to near-continuous noise during the operation of the turbines, at levels which do not constitute a statutory nuisance or exceed planning conditions, but which are clearly disturbing and unpleasant and may have some psychological effects11.”
In addition to audible sound turbines produce sound in the 1 to 16 Hz range which is perceived by humans as vibration. Possible adverse reactions include insomnia and sleep disturbance, loss of concentration and disequilibrium12. These effects, described as a seemingly incongruous constellation of symptoms have been christened Wind Turbine Syndrome13. Some studies have recommended far greater separation distances between turbines and dwellings than the 300 to 500 metres which developers often claim to be adequate, with up to 5km being necessary to ensure residents do not suffer the effects of exposure to infra-sound9.
The sight of these immense structures, in areas of outstanding natural beauty, often represents a blot on the landscape and some National Parks refuse permission on those grounds alone. When considering the visual impact care needs to be taken to appreciate the way in which developers present their photo-montages, producing panoramic images with wide angles lenses. Lenses with a short focal length have a wide horizontal field of view and this makes structures appear smaller and more distant than with a normal camera. For example, most photo-montages have a 75 or 90 degree field of view whereas a standard lens on an SLR camera would be between 30 and 35 degrees. The camera does not lie if its language is understood.
Just because we are told something loudly and often does not mean that we should accept it without question â€“ especially when those who seek to tell us what we should believe will themselves benefit from our acceptance of their arguments. Such is the case with any product or service which is described as ‘environmentally friendly’. We must always ask ourselves who stands to benefit? Usually the answer will be not us!
Achieving energy security in the long term will be a challenge and sources of power loosely described as ‘renewable’ have a part to play. Our rivers, for example, offer the potential for hydro-electric generation and are a much less erratic source of energy than the wind. Solar power may not seem an obvious choice for the UK but even here, with advances in technology, it can play a part and is also predictable. Wave and tidal power has potential and predictability on its side. Yet for all its disadvantages and the problems it causes it is wind power which seems to be regarded as a latter day philosophers’ stone which will turn air into electricity. We should reflect that the last philosophers’ stone was conspicuously unsuccessful in turning lead into gold for if it had been we would not now have a budget deficit.
There is a flicker of light at the end of the tunnel and this at least is not caused by the strobing of a wind turbine. In early 2012 the Government, under pressure from Conservative backbenchers, reduced the feed-in tariff by 10% with hopefully further cuts to follow and with the subsidy reduced these schemes will look less and less profitable. Energy Minister Greg Barker also said:- We inherited a policy from the last government which was unbalanced in favour of onshore wind. There have been some installations in insensitive or unsuitable locations too close to houses or in an area of outstanding natural beauty.14
However we produce our energy in the future, the answer is not blowing in the wind!
- Abalain, Chazal & Schumpp 2007.
- Vent de Colere.
- Yorkshire Post 19th April 2007
- Ministere de la Defense Francaise. Answer to Parliamentary question 105146 26th September 2006
- Washington Post 10th June 2006
- British Horse Society April 2010
- â€œRelationship Between Bats & Wind Turbines in Pennsylvania & West Virginia.â€ Edward B. Arnett, Bat Conservation International; Wallace P. Erickson, Western Ecosystems Technology; Jason Horn, Boston University; Jessica Kerns, University of Maryland.
- Marjolaine Villey-Migraine, University of Paris.
- Study by the University of Groningen.
- Report from the Welsh Affairs Select Committee
- H. Moller, Journal of Low Frequency Noise, Vibration and Active Control. Vol. 21.2
- Wind Turbine Syndrome by Dr. Nina Pierpont MD PhD.
- Sunday Times 15th April 2012.
First published 2010 www.expertopinions.org.uk