Clean Energy FAQs

How efficient are wind turbines?

Using a free and infinite fuel source - the wind - to meet our power needs is about as efficient as you can get. The technology is efficient too. Modern wind turbines generate electricity 70-85% of the time, cutting in when the wind is around 5mph, and cutting out to avoid damage when it reaches 56mph. Anti-wind campaigners often make much of the fact that over the course of the year they will generate around 30% of their theoretical maximum output (1). This is known as the load factor. The load factor of conventional fossil fuel power stations is on average 50% (2). A turbine typically pays back the energy consumed in making, installing, operating and decommissioning it in the first 3-5 months of its 20 year life (3).

Will turbines make any difference to climate change?

Every unit of power generated by a wind turbine displaces a unit of power that would otherwise come from a fossil-fuel power station and therefore reduces greenhouse gas emissions. While some fossil-fuel back up is needed because of the intermittent nature of wind power, this will be minimal and still result in an overall reduction in greenhouse gas emissions.

Noise and wind turbines

Noise, quite rightly, is one of the issues our neighbours are most worried about.

Early 1980s-vintage wind turbines were noisy, because their rotors were downwind of their towers. Modern wind turbines, whose rotors are upwind of their towers, are surprisingly quiet. You can stand right underneath the blades and still hold a conversation without raising your voice. For planning, we had to do a study of the effect of the noise on our nearest neighbours. This included placing microphones close to the nearest houses for 28 days to see what the background noise levels were, and then doing a modelling exercise to see how they would be affected. The study showed that both at night and during the day, the sound of the turbine should be below that of the noise limits set by strict planning guidelines at all wind speeds. This doesn’t mean the closest neighbours won’t be able to hear it at all, but that their enjoyment of their homes and gardens should not be affected. The highest figure projected was 39.1 decibels, at the closest property, at a single windspeed.

Table 1 Noise generated by wind turbines compared with other everyday activities
Source/Activity Indicative Noise Level dB(A)4

Threshold of Pain 140
Jet aircraft at 250m 105
Pneumatic drill at 7m 95
Truck at 30 mph at 100m 65
Busy general office 60
Car at 40 mph at 100m 55
Wind farm at 350 m 35–45
Quiet bedroom 20
Rural night-time background 20 – 40
Threshold of hearing 0

There is no low level vibration or imperceptible infrasound from turbines that affects pacemakers.

Aren't most people against wind turbines?

Despite what you might read in the papers, wind power is popular with the general public and with communities in which wind farms are already operating. In the UK approval is over 80 per cent among those within five kilometres of a wind farm (5). Furthermore, there is evidence following a comprehensive study by the Scottish Executive that those living nearest to wind farms are their strongest advocates.

Research at our public exhibition at Trethurgy Village Hall in August backs this up. When asked "How do you feel about Eden’s Clean Energy Project proposal?" 72% of those who visited the exhibition said they supported it, 58% unreservedly and 14% ‘with reservations.’

Shadow flicker

Some people have raised concerns about “shadow flicker”. Turbines can cast flickering shadows when the sun is behind them. As this can be annoying, planning requires that a shadow flicker study is carried out. Our survey found that only seven of our closest neighbours could be affected for more than 30 hours a year, and then only if the sun was out. Concerns have been raised that shadow flicker could trigger epilepsy. This is not the case, as the danger would only occur if blades turned at over 50rpm, and this turbine would turn at 15 rpm.

Do wind turbines affect property prices?

The evidence for wind turbines affecting house prices badly is patchy and ambiguous. In 2007, RICs (The Royal Institution of Chartered Surveyors) did a study in Cornwall. They found that "despite initial evidence that there was an effect, when they investigated more closely, there were generally other factors which were more significant than the presence of a wind farm." In the US, a study that examined 24,300 property transactions found that there was no evidence to suggest that wind turbines negatively affected value, instead positively affecting them. (6) However, in July this year, a house in Lincolnshire did have its council tax banding reduced, but this was a property on a plain with eight turbines in clear sight. The tax band was reduced on the grounds of noise.

Is wind power expensive?

No, wind is a very competitive source of energy generation. A study published in Wind Power Monthly (6) about the costs of generation around the world found that 'Wind is already competing with coal, it is cheaper than nuclear and cheaper to exploit at large scale than any of the other renewable energy sources. In some regions it can be competitive with gas-fired generation today.'

The generation costs of onshore wind power in the UK are around 3.2p per unit, with offshore at around 5.5p per unit. This compares to a wholesale price for electricity of around 3.0p per unit.(7)

The future looks bright for wind power as the cost of generation is likely to fall due to greater investment and fast improving turbine technology, and the fuel, wind, is free and infinite. In contrast, the cost of fossil fuels like gas and oil are likely to rise as natural reserves are depleted. When the social and environmental costs of greenhouse gas emissions and climate change are taken into account, the cost of wind power is even lower.

Are there any health implications of living near to a wind farm?

No, none. Turbines do not produce any emissions, harmful pollutants or waste products that could damage health or wildlife. Despite claims that infrasound (sound with a frequency too low to be heard) may damage health, many reports have been published dispelling this claim. In fact, it is often the case that evidence for health impacts of low frequency noise come from misrepresentations of reports. One DEFRA report by Dr Geoff Leventhall (9) is so often misrepresented by campaigners that he was prompted to say: 'I can state quite categorically that there is no significant infrasound from current designs of wind turbines. To say that there is an infrasound problem is one of the hares which objectors to wind farms like to run. There will not be any effects from infrasound from the turbines.'

RES follows strict Health and Safety guidelines during the development, construction and operation of all their turbines.

Horses, Bats and Birds

The RSPB views climate change as the most serious long-term threat to wildlife in the UK and globally, and therefore supports the government’s renewable energy targets. They say, 'Appropriately positioned wind farms do not pose a significant hazard for birds.' (10) We have carried out bat and bird surveys, both of which concluded that the impact on local populations should be low. As for horses being spooked by the turbine, the Delabole wind farm is built on a stud farm. Horses are ridden directly underneath the turbines with no adverse effects.

What about Eden using other alternative energy sources?

Eden already has a biomass boiler that can produce its baseload heat, some solar photovoltaics on our educational centre, The Core, and a small wind turbine. We have investigated all other renewable energy sources, along with our consulting engineers Buro Happold and have come to the conclusion that for our electricity needs, a single large turbine is the best course at the moment. Other technologies such as solar photovoltaics are either too expensive (£26 million), not available enough (hydropower), or not yet certain enough. (geothermal: £15 million for drilling, no guarantee of electricity at the end of it)

Further information:

'Wind Power in the UK'™ by the Sustainable Development Commission, May 2005, and accompanying summary booklet 'Wind Power - Your Questions Answered', both available to download from http://www.sd-commission.org.uk

'Wind Power: your questions answered,' Friends of the Earth, 2003. http://www.foe.co.uk/

References

Sustainable Development Commission (2005) Wind in the UK
SERA (2005). Our Energy Future: The Role of Wind Power
Sustainable Development Commission (2005) Wind Energy in the UK
HMSO (2004) Planning for Renewable Energy. A Companion guide to PPS22
Sustainable Development Commission (2005) Wind Energy in the UK
What is the impact of wind farms on house prices? March 2007 www.rics.org/RICSWEB/getpage.aspx?p=dqV5h4HTMkOqBCp1Q6GPlg
NOP World, August 2004
Wind Power Monthly (January 2004) " Wind Becomes Respectable"
Sustainable Development Commission (2005), Wind Energy in the UK
EECA (2004), Low Frequency Noise and Infrasound from Wind Turbine Generators: A Literature Review, Bel Acoustic Consulting
Defra (2003), A Review of Published Research on Low Frequency Noise and its Effects, Dr Geoff Leventhall
RSPB www.rspb.org.uk/ourwork/policy/windfarms/index.asp

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