Environmental Impacts of Wind Farms: Myth and Reality

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:

1. Greenpeace
2. EWEA
3. CRES