Environmental
Impacts of Wind Farms:
Myth and Reality
E. Binopoulos, P. Haviaropoulos
Centre for Renewable Energy Sources (CRES)
In
recent years, there has been a spectacular increase in installed power capacity
from wind turbines in Greece
(Crete, Evia, the islands). The very rapid development of wind energy was
accompanied, inevitably, by concern in local communities over the possible
impact of wind turbines on the environment.
In some cases, the fears expressed seem somewhat exaggerated and
sometimes, unrealistic. In still other
cases, the objections to the installation of wind turbines or wind farms are
valid to some extent and warrant further investigation. In any event, however, the acceptance or
rejection of wind energy by local communities depends on their being
objectively informed of the benefits and possible impact of it as yet another
human intervention in nature.
First,
let us examine the exact reasons for this rapid development of wind energy, not
only in Greece
but in the rest of the world. Today, it
is commonly accepted that global climate
change is one of the greatest threats to the future of mankind. This change is due in large part to emissions
of so called “greenhouse gases” which inevitably result from the production of
energy using conventional fuels. It is
considered to be a fact that the development of renewable energy sources and
especially wind energy is the only – non nuclear – medium term solution to the
problem of climate change.
However,
generally speaking, what are the benefits from the use of wind energy?
- The wind is an
inexhaustible energy source and nature provides it for free.
- Wind energy is a
technologically mature, economically competitive and environment friendly
energy choice.
- It protects the
Earth, as every kilowatt hour produced by the wind replaces a kilowatt
hour produced by conventional generating plants, which pollutes the
atmosphere with greenhouse gases.
- It does not
burden the local environment with dangerous gas emissions, such as carbon
monoxide, sulfur dioxide, cancer causing microscopic particles, etc. as
conventional electricity generating plants do.
- It enhances
energy independence and security which is especially important for Greece and
Europe in general.
- It contributes
to the decentralization of the energy system, reducing energy transmission
losses.
So, wind energy has many positive aspects. However, what if its negative impacts on man
and the environment are worse even than those from conventional (nuclear, coal)
generating plants as some maintain?
Below we will attempt a rational – technical approach to this question.
In the beginning, it would be useful to take a brief
look at the main parts of a modern wind turbine, at the same time dispelling
any distorted notions.
A wind turbine consists of the following main parts:
1. The tower:
It is cylindrical, built of steel and usually consists of two or three
joined sections. The construction is
similar to that of the towers which support the lights at stadiums and on
national highways.
2. The control box which contains the mechanical
subsystems (main axle, braking system, gear box and electrical generator):
·
The main axle
with the braking system is similar to the wheel axle of a car with hydraulic disc
brakes.
·
The gear box is
similar to that of a car, the difference being that it has only one gear.
·
The electrical
generator is similar to those used by the Public Power Corporation of
Greece (PPC) in electricity generating stations with gensets or to small
portable generators.
3. Electronic
control systems for safe operation.
They are composed of
one or more subsystems of
microcontrollers and their “job” is to ensure
safe and regular operation
of the wind turbine in all conditions.
4. The blades are made of synthetic
materials (fiberglass and special
resins), similar to those
used in sailboats. They are designed to
withstand extreme
strains.
As a
necessary component for the functioning of a wind turbine as part of a wind
farm, we should also include the transformer which converts the low voltage
produced by the wind turbine to medium voltage so that the electricity can be
transmitted by the PPC grid. The
transformer is usually installed beside the wind turbine and is no different in
construction from the transformers attached to PPC electricity poles, often
only a few metres away from residential buildings.
From
the above description, it is clear that a wind turbine is composed of simple
subsystems and that it is only a machine whose purpose is to convert energy
from the wind to electricity (that is the definition of a wind turbine). We could also liken a wind turbine to a small
electricity generating plant – only that it uses the wind as a “fuel”.
Let
us now examine the most common concerns about negative impacts that the
installation and operation of wind turbines in wind farms could have.
A. Do wind turbines create noise problems?
This
is the only substantial problem, but it is the easiest to control and
prevent. In wind turbines, the noise
emitted can be divided into two categories according to its origins: mechanical and aerodynamic.
- The first type
is produced by the moving mechanical parts (gear box, electrical
generator, bearings, etc.)
- The second type
is caused by the revolutions of the blades.
Modern
wind turbines are very quiet machines in relation to their power and through
their manufacturers’ continuing improvements keep getting quieter. The problem of noise is corrected either at
the source or during the course of operation.
Mechanical noise has been minimized at the design stage (side toothed
gear wheels), or by acoustic insulation on the inside of the turbine
housing. Also, mechanical noise can be
corrected during operation by acoustic insulation curtains and anti vibration
support footings. Aerodynamic noise can
be corrected by careful design of the blades by the manufacturers who make
minimization of this type of noise a top priority.
The
level of audible noise from a wind turbine, built to modern specifications, at
a distance of 200 metres, is lower than the background noise level of a small
town in the countryside and of course is not a nuisance. Given the requirement under Greek law that wind
turbines be installed at a minimum distance of 500 metres from residential
areas, the level is even lower and corresponds to that of a quiet living
room. In addition, at the wind speeds in
which wind turbines operate, the natural noise (noise of the wind in trees and
bushes) covers any noise emanating from them.
Keeping
the foregoing in mind along with the sites where wind farms are usually built
in Greece
for optimization of output, we can state with certainty that wind farms do not
cause:
- An increase in
the existing noise level outside their boundaries and even less in
residential areas.
- Exposure of
people to a high level of noise.
The
easiest and most effective way to convince someone about supposed wind turbine
noise is a visit to a wind farm on a day when all the wind turbines are
operating normally.
B. Do wind
turbines create electromagnetic interference problems?
This
concern is usually about problems caused by the location of wind turbines in
relation to existing radio or television stations on the one hand, and on the
other, to possible electromagnetic emissions produced by the turbines.
It
is a fact that the transmission from radio or television broadcast frequencies
(mainly FM broadcast frequencies) is influenced by obstacles between the transmitter
and the receiver. The main problem
created by wind turbines is caused by the moving blades which can result in
signal variations due to deflection.
This effect was more of a problem with first generation wind turbines
which had metal blades. The blades of
modern wind turbines are made exclusively of synthetic materials which have a
minimal impact on the transmission of electromagnetic radiation.
Greek
law stipulates that a license for a wind park will only be granted if some
minimum distances are kept from telecommunications or radio and television
stations. Any possible interference
problems can be prevented by proper design and location or corrected at a
relatively low cost by the builder of the wind farm through a series of simple
technical measures, such as the installation of additional transmitter
masts. With regard to compatibility and
interference in telecommunications, it is worth mentioning that in other
European countries, wind turbine towers not only do not create obstacles, but are
already being used for the installation of aerials to improve communications
services, such as mobile telephone service!
As
for radiation emitted, it is obvious from the description of the parts of a
wind turbine that the only subsystems which could possibly “emit” low level
electromagnetic radiation are the electrical generator and the medium voltage
transformer. The electromagnetic field
of a wind turbine is extremely weak and is confined to a very short distance
from the exterior turbine housing which is at least 40-50 metres above the ground. For this reason this, there is no exposure to
electromagnetic radiation at all, and especially not at the base of the wind
turbine. The transformer is always
surrounded by a security fence or is enclosed by a metal shed. The fence is placed at a distance where the
level of electromagnetic radiation is negligible. Therefore, we can confidently state that
rumours about radioactive emissions or other types of radiation from wind
turbines are baseless.
C. Do wind
turbines ruin the landscape?
This
question has generated a great deal of publicity.
Visual
disturbance is subjective and it
is difficult to set standards which will be accepted by everyone. From research in European Union countries, it
was found that people who are favourably disposed to the development of wind
energy accept the sight of wind turbines much more easily than people who are
opposed to it from the beginning. In the
same studies, it was also found that wind farms are visually more acceptable to
people who have been informed of the benefits derived from their use. If a simple comparison is made between a
thermal production plant (i.e. lignite), and a wind farm, it is obvious that
the visual disturbance from the former is conspicuously and objectively much
greater. Of course, given that wind
turbines are naturally visible from a distance, it is important that the
special characteristics of each installation site are taken into consideration
and an attempt made to blend them into the landscape.
D. Do wind
turbines affect farming and livestock?
There
is no indication that wind farms have a negative impact on farming or
livestock. Given that almost 99% of the
land on which a wind farm is built is available for other uses, it is clear
that farming can continue after the wind farm has been built. The usual sites for wind farms are in
mountainous areas with low vegetation due exactly to the high wind speeds which
favour wind energy development. In these
areas, the land is used mainly as pasture for sheep and goats, which can
continue unhindered after the wind farm has been built. In fact, in some wind farms, it has been
observed that wind turbines attract sheep and goats in hot weather because they
enjoy the shade provided by the towers!
E. Do wind
turbines affect bird populations?
Flying
birds sometimes run into buildings and other permanent structures. Wind turbines, however, do not cause a
particular problem as has been demonstrated by studies done in other European
countries, such as Germany,
the Netherlands,
Denmark
and England. Specifically, it was calculated that out of
the total number of birds killed in a year, only 20 deaths were due to wind
turbines (for an installed capacity of 1000MW), while 1500 deaths were caused
by hunters and 2000 caused by collisions with vehicles and electricity
transmission lines (they are almost “invisible” for birds). Of course, the protection of birds in
ecologically sensitive and protected areas must be taken into consideration in
the planning and location of a wind farm.
Summing
up, it is important to understand that whatever impacts wind turbines have, on
the one hand they are very obvious, and on the other, it is possible to
minimize them through proper design and planning. In contrast, the impacts of thermal or
nuclear energy production are slow to appear, are long term and no matter how
much effort and money are spent, it is impossible to minimize them. In
conclusion, we must decide that if we have to produce electricity, it is
certainly preferable to produce it in a way which has the smallest possible
impact on the environment. From a
technical and economic standpoint, the most mature form of renewable and
“clean” energy is wind energy. It can
effectively contribute to combating climate change while at the same time
providing various environmental, social and economic benefits.
Sources
of statistics:
- Greenpeace
- EWEA
- CRES
