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Wind turbine - Frequently Asked Questions
"I kind of like
the thought of turbines going round."
Are wind turbines noisy?
No. Thanks to advances in wind
turbine technology, well designed, well sited
turbines can be quiet enough to be virtually
inaudible
to people just a few tens of metres away. At
these distances, any noise they do make is usually
drowned out by the natural noise of the wind itself
in the trees and vegetation. To protect nearby
residents, wind turbines are required to meet strict
noise standards.
Having read exaggerated claims in the press, people
visiting wind farms are often surprised at how quiet
they actually are. The Scottish Executive public
opinion survey is one of several demonstrating that
concerns about noise are often unfounded. 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 1% thought they were noisy.
For more information: see the BWEA fact sheet on
noise:
www.bwea.com/ref/noise.html
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 25 year lifetime a wind turbine will produce over
100 times more energy than was used in its
manufacture. And of course once operational - unlike
other generating technologies - windpower produces
no further CO2
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 huge 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 capacity in it simply to
handle the huge fluctuations in demand which happen
during normal operations - regardless of wind
power. Back-up is needed for all forms of energy
generation because of unexpected increases in demand
(for example, the advert break in
Coronation Street) - or if, as can happen, a large
conventional or nuclear power station has to be
taken offline at short notice.
The way in which wind power
"displaces" other generating capacity on the network
is now well understood by power engineers and it is widely accepted that
whilst wind makes up less than about 20% of the
generating capacity on the grid no further backup is
needed. Far higher levels of wind power
are possible, but some backup would probably be
needed, but this could easily be provided by other
renewable sources such as hydro. In fact, Norway -
which is rich in hydro-power and Denmark which is
rich in wind-power have an arrangement where they
back each other up in terms of the ebbs and flows.
New "smart grid" technologies
are another emerging solution to this issue where
non time critical loads - such as battery charging
for vehicle fleets - are automatically controlled by
the network on a minute by minute basis to regulate
demand in line with supply. Barack Obama has
recently pledged to build such a "smart grid" across
the US and
plans already exist for a similar
pan-European supergrid.
How popular is wind energy?
Very popular indeed. 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
this data on the MORI website.
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. Most people
realise that building more wind farms is vital for
tackling climate change and that the United Kingdom
should be ready to embrace these developments.
The visual effect of wind farms is
very much a matter of personal opinion, 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 intelligent discussion of the issues
is forgotten and supporters of the schemes are
intimidated into silence.
Have a look at the web site of
one 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.
Do wind turbines affect
radar?
Potentially, yes. Radar used
for air traffic control sweeps the horizon every
four seconds. It is likely therefore that each time
the radar illuminates the wind turbine the blades
will be in a different position and the radar will
be confused into thinking that it is a moving object
thereby creating 'clutter' on the screen. Technical
solutions to this problem are well known and include
using a special "stealth" coating on the blades,
similar to that used on stealth aircraft, and
enhancing the radar illumination frequency of the
windfarm to 10 times per second which is sufficient
to clearly differentiate the moving blades from a
moving aircraft.
In Germany there are
approximately 21,000 wind turbines, many of them
quite close to air bases. So apparently German air
traffic controllers and pilots are well able to
master the art.
How big are they?
By and large bigger is better.
Each new generation of wind turbines is bigger than
the last as technology improves and engineering
problems are solved. The current generation of 2MW
turbines - as proposed for Maer Hills - have a hub
height of about 120 metres and a blade length of
about 65 metres. On the drawing board are larger
more efficient turbines with blade lengths up to 100
metres generating up to 10MW.
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.
Nearly all wind turbines have three blades
simply because this is the most efficient
configuration. The turbine's control systems
constantly face the blades
into the wind. As 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 m/s
(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.
Average wind speeds predicted
for Maer Hills are around 7 m/s.
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 now operate at variable
speed for maximum efficiency. The crucial factor is the so-called
"tip-speed ratio" which means that for aerodynamic reasons
and for maximum efficiency the speed of the blade tips
is linked in
proportion to the wind speed. Hence large turbines
with long blades rotate at lower RPM.
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?
Like most renewable sources the wind is a diffuse form of energy,
hence the size of the turbines needed to collect it. The
area a wind farm requires depends on the size of the
turbines and the site specific wind conditions.
As a rough guideline windfarms
generate around 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. But the UK is one of the
windiest countries in Europe. And the wind will
never stop blowing everywhere in the UK at once so we have a massive
natural resource
just waiting to be used. Electricity is generated
using a whole range of different technologies. At
the moment, when the wind stops blowing, electricity
continues to be provided by other forms of
generation, such as hydro-electricity, gas, coal
or nuclear. In the future, all our electricity will
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.
Various 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, smart grid
technology and hydrogen production 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
e.g. for hydrogen powered vehicles.
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?
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
this would be detected by the turbine's management
and 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?
No. But what can cause
problems is the erosion of confidence that anti-wind
campaigning in the area produces as campaigners
"talk down" property 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 any 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.
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?
Yes of course - 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 other fuels like 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.
Send
us your news and comments!
maerhills@hotmail.co.uk
and spread the word!
Maer Hills Action Group
set up by
local people in response to the proposal to build wind turbines at
Maer Hills
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