Windpower - Frequently Asked Questions
Do wind turbines frighten livestock?
Wind farming is popular with farmers, because their land can
continue to be used for growing crops or grazing livestock. Sheep,
cows and horses are not disturbed by wind turbines. They habitually
graze under wind turbines, and seek shelter around them. For example
the first wind farm built in the UK, Delabole in Cornwall, is home
to a stud farm and riding school, and the farmer, Peter Edwards,
often rides around the wind farm on his horse.
How long does it take for a turbine to 'pay back' the electricity used to manufacture it?
The comparison of energy used in manufacture with the energy
produced by a power station is known as the 'energy balance'. It can
be expressed in terms of energy 'pay back' time, i.e. as the time
needed to generate the equivalent amount of energy used in
manufacturing the wind turbine or power station.
It is estimated that the average wind farm will pay back the
energy used in its manufacture within three to five months, and over
its lifetime a wind turbine will produce over 30 times more energy
than was used in its manufacture. This is faster than coal-fired power
stations, which take about six months. When the energy used to
supply the fuel for coal power plants is included, the energy
balance for those conventional sources is clearly even poorer still,
as coal-fired power stations continually produce C02.
How safe is wind energy?
Wind energy is safe and, unlike coal-fired power stations, they do not produce toxic cancer causing dioxins,
or the particulate pollution in the air that is highly damaging to human health. Nor do they contribute to climate change - the biggest environmental threat we face, a bigger threat than global terrorism according to the UK Government's Chief Scientist.
Safety levels for construction and maintenance staff are similar to equivalent industries.
Will building wind turbines help prevent global warming?
Yes.. Carbon dioxide (CO2) is the most important of the greenhouse
gases which are changing our climate.
If we are to avoid dangerous levels of climate
change, a phase out of fossil fuels (coal, oil and gas) is
necessary. That means switching to forms of energy generation
that do not produce CO2.
Wind power is a clean, renewable form of energy which, during
operation, produces no carbon dioxide. While some emissions
of these gases will take place during the design, manufacture,
transport and erection of wind turbines, enough electricity
is generated from a wind farm within a few months to totally
compensate for these emissions. When wind farms are dismantled
(usually after 20-25 years of operation) they leave no legacy
of pollution for future generation.
Given the scale of the CO2 cuts needed, wind power - as the
cheapest, most developed renewable energy technology, and
the fastest to build - is the best placed renewable technology
to deliver carbon cuts on a large scale, quickly.
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 common among anti-wind
campaigners. Their argument runs like this:
"Because wind power is intermittent (it varies with the
weather) it needs dedicated back-up for when the wind doesn't
blow. This back up will be coal powered stations that have
to be kept 'spinning' (ie burning) at low level so they are
ready to go immediately that the wind drops. Burning like this
is inefficient so the emissions they make are roughly the same
as if they were actually generating electricity. Therefore
wind power saves no carbon because the back-up emits the same
as if there were no wind turbines in the first place."
This argument is, quite simply, wrong. The national grid has
back-up on it regardless of wind power. Back-up is needed for
all forms of energy generation because of unexpected increases
in demand (a cold snap for example, or the advert break in Coronation Street).
It is widely accepted that only very minor levels of back-up
are needed for wind - up to about 20% wind on the system (much
higher levels of wind power are possible, but require a little
more back-up). In terms of emissions - even if the back-up
was the dirtiest option - coal power - at 10% wind power on
the system only 1% of the CO2 saved by the wind would be emitted
from the back-up - and 99% is saved and coal is not the only option
for back-up.
How popular is wind energy?
It's popular. Wind energy is one of the most popular energy technologies. It's easily understood
- everyone can see how they work and in spite of their size they are non-threatening - no
large buildings with no obvious purpose and no huge chimneys and cooling towers, as with conventional power stations.
Whilst some residents may be apprehensive about any proposed local wind developments.
When accurate information and knowledge is made available, experience shows that the
initial concerns are reduced and support for wind farm schemes increases.
A poll undertaken in Scotland shows for example that before construction of the Scottish wind farms studied,
12% of people living near the sites thought that the turbines would cause a noise nuisance, but after construction,
when people had experience of the wind farm operating, only 2% thought they were noisy (See here).
Why is there opposition to wind farms?
Local opposition to proposed wind farms usually arises because some people perceive
that the development will spoil the view that they are used to. It is true that a
large wind farm can be a significant change, but 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 increased utilisation of renewable energy and greater use of wind power will
mean that we will have more of these structures visible in our townscape and
landscape in the future. But Cambridge Friends of the Earth believe that
building more wind farms is vital for tackling climate change and that the United Kingdom
should be ready to embrace these developments - obviously whilst following sensible
siting criteria.
The visual effect of wind farms is a subjective issue, but most of the other
criticisms made about wind energy today are exaggerated or untrue,
and simply reflect attempts by particular groups to discredit the technology,
worry local communities and turn them against renewable energy schemes.
Anti-wind groups have been particularly effective at using local media,
and have been able to create highly emotive and divisive reaction in local
communities, where sensible discussion of the issues is forgotten.
Have a look at the web site of the most prominent anti wind group
(Stop Cambridgeshire Windfarms) to see
the above points in action.
What are wind turbines made of?
The towers are mostly tubular and made of steel, generally painted light grey. Some towers are made of concrete. The blades are made of glass-fibre reinforced polyester or wood-epoxy. They are light grey because this is the colour which is most inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.
How big are they?
Large modern wind turbines have rotor diameters ranging up to 65 meters while smaller machines (around 30 meters) are typical in developing countries. Towers range from 25 to 80 meters in height, with offshore turbines generally at the larger end of the scale.
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.
For more information see:
The animated website
Wind with Miller
produced by the Danish Wind Industry
Association for kids and young at heart of all ages.
It's a fast and fun way to get an intuitive grasp of advanced wind power knowledge.
A very informative and more technical version can also be found at the
website of the
Danish Wind Industry Association
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 16 kilometres an hour - ie. a "gentle breeze", where leaves and small twigs
on trees are in constant motion) and reach maximum power output at around 15
meters/second (around 54 kilometres per hour - ie. "strong breeze" to "near gale"
- when whole trees are in motion, and it becomes hard to walk against the wind).
At very high wind speeds, i.e. gale force winds,
(25 metres/second, 90+ kilometres/hour) wind turbines shut down.
How fast do the blades turn?
The blades rotate at anything between 15-50 revolutions per minute at constant speed.
However, an increasing number of machines operate at variable speed.
For more technical information: see the
New Zealand Wind Energy Association's factsheet on
wind energy or have a look at the very informative wind energy website of the
Danish Wind Industry Association
How much space do wind turbines require?
The wind is a diffuse form of energy, in common with many renewable sources.
The space a wind farm requires depends on the size of the turbines and
the specific site conditions.
A rough guideline for the required space is 10 MW per 1 km2,
but only 2-3% of this land area would be occupied by the turbines and access tracks.
The remainder can be used for other purposes, such as farming or as natural habitat.
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.
At the end of their lives, they can be decommissioned within a couple of days
and replaced with newer designs.
The very first of the mass-produced turbines celebrated its 20th birthday in May 2000.
This Vestas 30kW machine has operated steadily throughout its lifetime, and so far,
none of the major components have had to be replaced.
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,
such as gas, coal hydro-electricity or nuclear. But the UK is one of the windiest
countries in Europe, so we have a massive resource waiting to be used.
In the future, all our electricity could come from a mix of complementary
renewable sources - balancing wind power with hydro, solar, geothermal,
biomass, wave and tidal power.
There is actually 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 plants 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 than the
intermittency of wind power, 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.
And the wind will never stop blowing everywhere in the UK at once.
Different overseas studies have sought to determine the limit beyond which
installing intermittent capacity (i.e. wind generators) starts to incur
significant costs in order to maintain the stability of the electrical grid.
The level varies but is typically 15-30% of the total installed capacity.
Of course we have to find out the maximum practical limit of wind energy on our
grid, but we're still a long way from it.
In future, hydrogen could offer a potential way of storing electricity from wind
power. Excess wind power can be used to produce hydrogen through electrolysis,
and then hydrogen can be turned back into electricity using a fuel cell,
as and when it is needed.
What happens when a wind farm is taken down or decommissioned?
At the end of their lives, wind turbines can be decommissioned and replaced
with newer designs - the technology will no doubt improve a lot over 25 years.
But if they are not to be replaced, then the way that a planning authority wishes
to have a wind farm decommissioned should be covered by clauses in its planning
permission.
These clauses typically require all above-ground visible traces of the wind farm to
be removed. This takes care of the turbines. Service tracks, if there are any,
could be removed, although it may be best to leave them. Obviously each case is
different, depending upon the size and geography of the development.
Developers will then comply with these clauses.
The concrete bases could be removed, but it may be better to leave them under the
ground, as this causes less disturbance. If so, they would be covered with peat,
stone or other indigenous material, and the site returned as closely as practicable
to its original state.
Compared to the problems associated with decommissioning a gas or coal-fired plant,
which leave a legaciy of toxic waste, tailings and unsightly buildings, let alone a nuclear power station,
decommissioning a wind farm is straightforward and easy.
Are wind farms harmful to our health as sources of infrasound?
Infrasound and Low Frequency Noise are established as real causes of
illness in some people, but there are no harmful infrasound effects
from wind turbines.
There are all sorts of sources of infrasound in the modern world such
as cars and other road traffic, aircraft, diesel engines, trains,
shipping, factories, combustion, artillery, mining and quarrying,
fridges and other household appliances, fans, compressors and pumps,
music, TVs, and air conditioning. Infrasound is also ubiquitous
in the natural environment from sources like air turbulence - even
from earthquakes and storms, sometimes thousands of miles away.
Extensive work has already been carried out on infrasound from wind
turbines, which demonstrated that "Low frequency noise and vibration
levels were both found to comply with recommended residential
criteria even on the wind farm site itself with the acoustic signal,
below 20 Hz, being well below accepted thresholds of perception."
In the words of infrasound expert John Leventhall:
"There are no harmful infrasound effects from wind turbines."
If a generator were to emit infrasound, the turbine tower would be
affected, noticeably vibrating, and although at below audible sounds,
this would be detected by the on board power control systems
which monitor the wind turbine and would automatically shut it off.
Tens of thousands of wind turbines have now been operating worldwide
for up to 20 years, including in some of the countries with leading
general studies on infrasound. No link or problem has been
identified with the presence of wind turbines in these studies.
For more information have a look at the literature review
"Low Frequency Noise and Infrasound from Wind Turbine Generators"
prepared for the EECA by Bel Acoustic Consulting.
Isn't wind power really expensive?
No. The cost of generating electricity from the wind has fallen dramatically over
the past few years. And energy from the wind will become even cheaper in the
future as greater experience is gained in manufacturing and developing this
relatively new technology. When the full costs of the environmental damage caused
by fossil fuels or nuclear power are taken into account, wind power is an even
better buy.
For example, it has been estimated that if the cost of environmental damage were
included, the price of electricity from coal would be three times higher than
electricity from the wind. The planned carbon tax
tries to internalise these negative externalities and will make fossil-fuelled
forms of generation less attractive and more expensive.
Do wind farms create jobs?
Yes. The New York State Energy Research and Development Authority even
estimates that wind energy produces 27% more jobs per kilowatt hour (kWh)
than coal and 66% more jobs than natural gas without the negative health and
environmental impacts such as air and water pollution and landscape destruction.
Additionally, 97% of the land occupied by wind farms
can continue to be used for grazing etc.
See:
Mazza, Patrick. 2001 . "Harvesting Clean Energy for Rural Development: Wind"
Climate Solutions Special Report. Olympia: Climate Solutions.
See also: Windflow Technology Ltd.
www.windflow.co.nz
Do wind farms affect house prices?
In an extensive study the Renewable Energy Policy Project (USA) examined price
changes in property values of ten projects. They found that
for the great majority of projects the property values actually rose more
quickly in the view shed after the projects came on-line than they did
in the comparable community. Moreover, values increased faster in the
view shed after the project came on-line than they did before." (1)
In the UK there are currently some 80 wind energy projects operating, and
survey evidence to date does not reveal a negative trend in property values
amongst properties in proximity to wind farms. According to the Royal Institution
of Chartered Surveyors, there are no studies that suggest an effect either way.
At Nympsfield in Gloucestershire, house prices continued to gain after plans for
the turbine were announced in 1992 and have continued to increase since the turbine
began operating in 1997.
This pattern is repeated at the 70 plus operating wind farms in England, Wales and
Scotland, where any evidence available demonstrates that wind farms have no material
effect on house prices; surveys in areas near to a wind project show 78% of
respondents reporting no difference in house prices, with some even reporting an
increase.
The only Australian study is an informal one on the Esperance wind farm at Salmon
Beach, a premier Western Australia residential area. The residential area was built
after the wind farm but still showed a strong trend of increasing house prices
throughout the estate over the ensuing years. In fact, local residents complained
at the proposal to decommission the wind farm at the end of its design life. (2)
For the latest UK news on this see the new report
by RICS and Oxford Brookes University
which finds no clear relationship between the proximity of wind farms and house prices.
For more overseas experience have a look at the US study
"The effect of wind development on local property values"
Notes:
(1) Sterziger G. et al (2003).
"The effect of wind development on local property value" Renewable Energy Project. Washington, USA.
(2) www.auswea.com.au
Isn't energy efficiency just as important?
Energy efficiency is essential. It is the other half of the solution to
the United Kingdom's energy needs. 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.
Energy efficiency enhances the benefits of renewables, by reducing the demand
on them and making their positive impact on carbon emissions greater and quicker.
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 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.
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