The Earth is surrounded by the atmosphere, which is made up of air. Air is a mixture of gas, and solid and liquid particles. Energy from the sun heats up the atmosphere and the Earth unevenly.

Cold air contains more air particles than warm air. Cold air is therefore heavier and sinks down through the atmosphere, creating high pressure areas. Warm air rises through the atmosphere, creating low pressure areas. The air tries to balance out the low and high pressure areas – air particles move from areas of high pressure (cold air) to areas of low pressure (warm air). This movement of air is known as the wind.

The wind is also influenced by the movement of the earth. As it turns on its axis the air does not travel directly from areas of higher pressure to areas of lower pressure. Instead, the air is pushed to the west in the northern hemisphere and to the east in the southern hemisphere.

Traditionally, wind speed is measured by anemometers – usually three cups that capture the wind rotating around a vertical axis. The wind direction is measured with weather vanes.

After measuring wind data for at least one year, the mean annual wind speed can be calculated. Wind speed and wind direction statistics are visualised in a wind rose, showing the statistical repartition of wind speed per direction.

A wind turbine is a machine that transforms the kinetic energy of the wind into mechanical or electrical energy. Wind turbines consist of a foundation, a tower, a nacelle and a rotor. The foundation prevents the turbine from falling over. The tower holds up the rotor and a nacelle (or box).

The nacelle contains large primary components such as the main axle, gearbox, generator, transformer and control system. The rotor is made of the blades and the hub, which holds them in position as they turn.

The towers are mostly tubular and made of steel or concrete. The blades are made of fibreglass, reinforced polyester or wood-epoxy. They are light grey because it is inconspicuous under most lighting conditions. The finish is matt, to reduce reflected light.

There are many factors at play when designing a wind farm. Ideally, the area should be as wide and open as possible in the prevailing wind direction, with few obstacles. Its visual influence needs to be considered – few, larger turbines are usually better than many smaller ones.

The turbines need to be easily accessible for maintenance and repair work when needed. Noise levels can be calculated so the farm is compatible with the levels of sound stipulated in national legislation.

Then, the right type of turbine must be chosen. This depends on the wind conditions and landscape features of the location, local/national rules such as on turbine height, noise levels and nature conservation, the risk of extreme events such as earthquakes, how easy it is to transport the turbines to the site and the local availability of cranes.

Wind turbines start operating at wind speeds of 3 to 4 metres per second and reach maximum power output at around 14-15 m/s. At very high wind speeds, that is gale force winds of 25 m/s, with special softwares this limit can reach up to 34 m/s, wind turbines shut down.The annual capacity factor of conventional power stations is on average 25%-40% in Turkey.

The optimum number of blades for a wind turbine depends on the job the turbine has to do. Turbines for generating electricity need to operate at high speeds, but do not need much turning force. These machines generally have three or two blades.

The majority of modern commercial wind turbines have three blades, as they produce the optimum amount of power.

Two bladed machines are cheaper and lighter, with higher running speeds which reduces the cost of the gearbox, and they are easier to install. They perform almost as well as three blade turbines. However they can be noisier and are not as visually attractive, appearing 'jerky' when they turn.

Turbines sometimes have to be stopped for maintenance, for repairing components or if there is a failure that needs to be checked. Another reason can be too little or too much wind: if the wind is too strong, the turbine needs to be shut down because it could be damaged.

Wind turbines can carry on generating electricity for 20-25 years. Over their lifetime they will be running continuously for as much as 120,000 hours. This compares with the design lifetime of a car engine, which is 4,000 to 6,000 hours.

The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor.

An average onshore wind turbine with a capacity of 4 MW can produce more than 12 million kWh in a year – enough to supply 10.000 average TR households with electricity.


The noise of wind turbines has been reduced significantly. Improved design has drastically reduced the noise of mechanical components so that the most audible sound is that of the wind interacting with the rotor blades. This is similar to a light swishing sound, and much quieter than other types of modern-day equipment. Even in generally quiet rural areas, the sound of the blowing wind is often louder than the turbines.