Opinion surveys in areas of the European Union with wind farms or many
wind turbines (such as Denmark and UK) indicate that 70 to 80 % of the
population is "generally supportive" or "unconcerned"
with respect to the wind turbines in their neighbourhood. In a referendum
in a Danish municipality with a very large number of wind turbines, 77
% of the votes favoured even more machines.
The political debate is often quite polarised. On the one hand, in many
countries the public in general favours renewable energy sources such
as wind power. On the other hand, deploying a wind farm in a local community
sometimes raises local resistance due to the neighbours' uncertainty and
negative expectations about the wind turbines. The public concern is often
about environmental effects of wind power such as visual intrusion, impact
on birds and birds' habitat, acoustic noise emission, safety, moving shadows,
etc. This has been called the NIMBY (Not-In-My-Back-Yard) dilemma.
In industrialised countries public acceptance of wind power is often
the most important planning restriction and consequently also a political
issue (Elliot, 1994). Experience in developing countries is still limited,
but recent large-scale applications in India and China show both reliable
production and a high degree of public acceptance along with private sector
participation (Andersen, Jensen, Beurskens, 1995).
The public concern is rooted in the fact that the environmental advantages
of wind power is on a global or national level, whereas, the environmental
disadvantages of wind power is on a local or neighbourhood level, associated
with the presence and operation of wind turbines.
Environmental advantages on a global or national level include:
No direct atmospheric emissions
No liabilities after decommissioning
Good energy balance
Limited use of land
Environmental disadvantages on a local or neighbourhood level, include:
Visual impact on landscape
Impact on birds
Interference with electromagnetic communication
Some of these disadvantages are of very limited significance. Quantifying
such advantages and disadvantages usually not included in economical analyses
of wind energy is often made by means of external cost analyses as we
shall see at the end of this paper.
No direct atmospheric emissions are caused by the operation of wind turbines.
The indirect emission from the energy used to produce, transport and decommission
a wind turbine depends on the type of primary energy used.
Liabilities after decommissioning
Electricity from wind turbines has no liabilities related to decommissioning
of obsolete plants. Today, most metal parts of wind turbines can be re-cycled.
In a very near future other parts, such as electronics and blades, will
be recycled almost 100p.c.
The direct environmental effects related with manufacturing of wind turbines
is similar to those of other equipment production processes, and the indirect
environmental effects of the energy used to produce a wind turbine depend
on the type of primary energy used. Several early investigations have
shown, that the energy invested in production, installation, operation
& maintenance and decommissioning of a typical wind turbine has a
"pay-back" time (energy balance) of less than a year of operation
(World Energy Council, 1994).
New up-dated surveys have confirmed this (Krohn, 1996). Manufacturing
a state-of-the-art 600 kW wind turbine takes 3.2 TJ taking into account
everything from producing raw material to installing a ready machine,
including 20 years of operation and maintenance and decommissioning. In
suitable locations, the wind turbine will generate 1.1 to 1.3 million
kWh per year in its projected 20-year useful life. The energy invested
in a state-of-the-art 600 kW wind turbine is therefore repaid over 3-4
Wind energy is diffuse and collecting energy from the wind requires turbines
to be spread over a wide area. As a rule of thumb wind farms require 0.08
to 0.13 km2/MW (8 - 13 MW/km2). The area needed for 100,000 MW is less
than 0.3% of the territory covered by the European Union. Onshore wind
farms have the advantage of dual land use. 99% of the area occupied by
a wind farm can be used for agriculture or remain as natural habitat.
Furthermore, part of the installations can be made offshore. Consequently,
limited area of land is not a physical constrain for wind power utilisation,
as it could be for large scale utilisation of biomass in energy production.
Acoustic emissions from wind turbines are composed of a mechanical and
an aerodynamical component, both of which are a function of wind speed.
Analysis shows that for most turbines with rotor diameters up to 20 m
the mechanical component dominates, whereas for larger rotors the aerodynamical
component is decisive.
The nuisance caused by turbine noise is one of the important limitations
of siting wind turbines close to inhabited areas. The acceptable emission
level strongly depends on local regulations. An example of strict regulation
is the Dutch regulation for 'silent' areas, where a maximum emission level
of 40 dB(A) near residences is allowed, at a wind speed of about 5-7 ms-1.
At this wind speed level the turbine noise is most distinctly audible.
In Europe a typical distance between wind turbines and the nearest house
is more than 150 or 200 meter.
Depending on the characteristics of the landscape modern wind turbines
with a hub height of 40 - 60 meters and a blade length of 20 - 30 meters
form a visual impact on the landscape. This visual impact, although very
difficult to quantify, can be a planning restriction in most European
A more objective case of visual impact is the effect of moving "shadows"
from the rotor blades. This is only a problem in situations where turbines
are sited very close to workplaces or dwellings. The effect can easily
be predicted and avoided through proper planning. A house 300 meter from
a modern 600 kW machine with a rotordiameter of 40 meter will be exposed
to moving shadows approx. 17-18 hours out of 8760 hours annually.
On the typical flat on-shore sites installation of wind turbines has
no erosional effects and the installation does not to any significant
level affect vegetation or fauna. In most countries wind power developers
are obliged to minimise any disturbance of vegetation under construction
of wind farms (in combination with road works etc.) on sensitive sites
such as mountainous sites and offshore.
Impact on birds
The impact of wind turbines on birds can be divided into:
direct impact including risk of collision and effect on the breeding
indirect impact including effects caused by disturbance from the wind
turbine (noise and visual disturbance). The disturbance effects of wind
turbines fall into three categories:
disturbance to breeding birds
disturbance to staging and foraging birds
disturbing impact on migration/flying birds
Studies in Germany, the Netherlands, Denmark and the UK conclude, that
wind turbines do not pose any substantial threat to birds (or bats or
insects). Bird mortality due to wind turbines is only a small fraction
of the background mortality (Still et al. 1994). A study has estimated
an maximum level of birds collision with wind turbines of 6 - 7 birds/turbine/year
(Clausager & Nøhr, 1995). In Denmark with approximately 4000
wind turbines this means that 25,000 to 30,000 birds annually die from
collision with wind turbines. As comparison it can be mentioned that over
one million birds are killed in the traffic in Denmark, and that the total
number of staging and migrating birds in Denmark is 400 - 500 millions.
Isolated examples have been reported of significant damages on specific
species, such as the Spanish wind farm of Tarifa near the Strait of Gibraltar,
which is a major bird migration route (Llamas, 1995). The problem was
caused by very special circumstances, and it seems to have been solved
without removing the turbines.
If not properly dealt with, wind farms sited on coastal sites can disturb
breeding and resting birds. Typically, an effect has been recorded within
250-800 meter, with a highest sensitivity recorded for geese and waders.
Including professional knowledge of birds and wind turbines in the planning
process or wind farms can solve this problem. A European Best Practice
for siting wind farms with respect to birds would be of great help for
European wind farm developers in avoiding disturbance of birds.
Interference with electromagnetic communication systems
Wind turbines in some areas can reflect electromagnetic waves, which
will be scattered and diffracted. This means that wind turbines may interfere
with telecommunication links. An investigation made by the British company
BBC concluded, that wind turbines' interference with electromagnetic communication
systems is no significant problem.
The IEA has provided preparatory information on this subject, identifying
the relevant wind turbine parameters (diameter, number and cross-section
of blades, speed, etc.) and the relevant parameters of the potential vulnerable
radio services (spatial positions of transmitter and receiver, carrier
frequency, polarisation, etc.). Planning of wind farms, areas where wind
turbines could interfere with telecommunication are normally avoided.
Accidents with wind turbines involving human beings are extremely rare,
and there is no recorded cases of persons hurt by parts of blades, parts
of blades or ice loosened from a wind turbines. Insurance companies in
USA, where most of the experience with large wind farms has been occurring,
agree that the wind industry has a good safety profile compared to other
energy producing industries. The International Electrical Committee (IEC)
has issued an international official standard on wind turbine safety.
Social or external costs
External or social costs of wind power (or other energy producing technologies)
are costs imposed on the society or the environment that are not accounted
for by the producers and consumers of energy (Eyre, 1994). Several international
surveys conclude that electricity from wind turbines has very low external
costs. Several methods can be applied to determine the external cost of
energy producing technologies and several ongoing research projects investigateexternal
costs of different technologies. In the European study "ExternE"
wind farms in the UK were analysed and the same method has been used in
Spanish wind farms. The results can be seen from table 4. As can be seen,
the total external costs of wind energy are of the order of 0.1 to 6.7
In a Danish study the external costs of wind power are compared with
those of N-gas, biomass and coal-burning plants (Meyer et al. 1994). As
can be seen from the table external costs of coal based electricity are
orders of magnitudes higher than for wind power.
The surveys conclude, that the most important impacts of wind farms are
noise and visual intrusion. These issues must be dealt with
when planing wind farms.