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How it work

Definition and Categories

Wind energy is the kinetic energy of moving air masses around the globe. The etymological root of the word ”  wind  “comes from the name of the mythological character Eole, known in ancient Greece as the master of the Winds. Wind energy is an indirect form of solar energy: solar radiation absorbed in the atmosphere result in differences in temperature and pressure.Thus the air masses begin to move and accumulate kinetic energy. It can be transformed and used for several purposes :

  • transformation into mechanical energy : the wind is used to move a vehicle (or boat yachting) to pump water (pumping windmills for irrigation or livestock watering), or to turn the wheel of a mill ;
  • the production of electrical energy  : the turbine is coupled to an electric generator to produce the continuous or alternating current. The generator is connected to a power grid or works in a “stand alone” system with an auxiliary generator (eg a generator), a battery bank or other energy storage device . A wind turbine is sometimes called a wind generator if it generates electricity.

Wind energy is a renewable energy that does not directly produce greenhouse gases during operation.

Operating modes of wind energy

  • The onshore wind called “onshore” are installed on the land.
  • Wind turbines called “offshore” are installed at sea.

A distinction is also two types of facilities  :

  • Industrial: large wind farms (or “wind farms”) connected to the electricity network;
  • Domestic: small wind turbines installed in private homes.

Technical or scientific operation

The process of conversion of kinetic energy into mechanical or electrical energy

The electrical or mechanical energy produced by a wind turbine depends on three parameters  : the shape and length of the blades, wind speed and finally the temperature affecting the density of the air.

The recoverable energy is the kinetic energy that can be extracted. It is proportional to the area swept by the rotor and to the cube of the wind speed.

Recoverable maximum power (P) is given by Betz ‘Law  : P = 0.37. S. V 3  ; where 0.37 is the constancy of the standard atmospheric pressure in air (1013 hPa), S is the swept area and V is the wind speed.

In practice, a wind turbine produces four times more energy if the blade is twice as large and eight times more power if the wind speed doubles. The air density also comes into play  : a wind turbine produces 3% more electricity if for the same wind speed, air is colder than 10 ° C.Wind power depends mainly on the intensity of the wind and its variations. Wind power is intermittent and unpredictable energy.

The wind is stronger and more consistent at sea. The wind turbines are also more powerful.

The entire blade / rotor is oriented into the wind by a rudder system. Most wind turbines start when the wind speed reaches about 3 m / s and stops when the speed reaches 25 m / s.Generally, wind turbines are set to exploit the intermediate power winds.

Issues in relation to energy

wind energy realismRegarded as a clean energy, wind energy is experiencing a major boom. Among the renewable energy is considered a mature technology and most economical after hydropower .

According to the Global Wind Energy Council, the installed capacity of the global wind farm was multiplied by 3 between late 2007 and late 2012. At that date (1) , it reached almost 282 GW, equivalent to the total capacity of nearly 280 nuclear reactors. Despite this growth, its share in the total world production of electricity is limited to 2.1% in 2011 (2) . In addition to the economic and environmental gives, wind energy is of particular interest because it can promote diversification and energy independence of a country . This energy source has its place in the future global energy mix, especially in countries that do not have significant fossil resources and / or developed nuclear energy industry. It is part of the implementation of alternative energy strategies despite the limitations it may have : randomness, its performance and its intrusion into the natural landscape.

The advantages of wind power

  • Wind energy is renewable and clean.
  • During the operational phase, this energy is almost completely independent of fossil fuels.
  • The land where the turbines are installed remains usable for industrial and agricultural activities. The plant can be dismantled relatively easily.
  • Their offshore development has significant potential.
  • Locally based, wind turbines can be used to respond to mass power requirements as to limited domestic needs, depending on the size of the turbine.

The problems

  • Wind energy depends on the power and accuracy of the wind.
  • This is an intermittent source of energy.
  • Development zones are limited.
  • Wind turbines can create conflicts of environmental use as visual and noise pollution.
  • There may be conflicts of use of land and marine space with other users (eg fishermen, boaters).

Major players


Countries settlors more total wind capacity

Backyard-Wind-Power jpgIt is Europe dominates the global wind energy market with 109 GW of installed wind capacity at the end of 2012 (3) . Germany alone accounts 31 GW albeit Denmark that has the output ratio / number of the most important people.

Worldwide, the United States overtook Germany in 2009 and have the end of 2012 with a capacity of almost 60 GW. In parallel, the Asian powers such as India and China want to develop their own industries. End of 2012, China would have a wind farm with an installed capacity of around 75 GW (with nearly 13 GW installed in 2012), surpassing the United States.

Each year, approximately 500 wind turbines were commissioned in France, about 1 GW, equivalent to the average power of a nuclear reactor.

The wind energy sector companies

In 2012, the global market shares of the leading manufacturers of wind turbines according to BTM Consult were as follows (4)  :

  • GE Wind (USA) with 15.5%;
  • Vestas  (Denmark) with 14.0%;
  • Siemens (Germany) with 9.5%;
  • Enercon (Germany) with 8.2%;
  • Suzlon (India) with 7.4%;
  • Gamesa (Spain) with 6.1%;
  • Goldwind (China) with 6.0%;
  • United Power (China) with 4.7%;
  • Sinovel (China) with 3.2%;
  • Mingyang (China) with 2.7%;

Measurement units and key figures

On average, a French consumes 7,756 kWh (total electricity consumption per population), an American 13,361 kWh while a Beninese consumes only 99 kWh (5) . By comparison, in Brittany, a 1 MW turbine power produces on average 2 million kWh per year (6) or a full operation of 2,000 hours per year, or 6 hours a day .

Wind power generated 10,400 jobs in France in 2009. 140 French industrial companies working in this sector. If the objectives of the Grenelle Environment Forum are required, the wind energy sector could reach 60 000 jobs in 2020 (7) .


From 2000 to 2012, the share of wind power in the total installed electric power increased from 2% to 11%. It reaches to the end of 2012 106 GW in the EU (8) .


In 2012, nearly 44.7 GW of new wind power capacity were installed worldwide. Wind power produces about 460 TWh in 2011, or approximately 2.1% of the total electricity production in the world. Experts GWEC (Global Wind Energy Council) plan to maintain a sustained growth of the wind, before eventually lead to a fleet capable of producing 3000 TWh in 2020.

Past and present

indeksThe beginning of the use of wind power dates back to approximately 3000 BC, in the context of the use of first sailing boats. After the first windmills were invented by the Persians around 200 BC. This technique is then imported in Europe and XII th century.

Two centuries after the famous Dutch windmills emerge. These mills are used to rotate sawmills or make oil. But it was in England that were advanced forms of the wings. England has the XIX th century about 10,000 mills. Since the 1990s, the technological development of wind allowed the construction of wind turbines.


Depending on the energy structure of the countries

Wind energy can integrate beneficially in countries whose energy production structure is based on fossil fuels. Its variability is offset by the availability of gas stations, oil or coal. This is for example the case of Germany.

However in countries whose energy production structure is based on sources less easy to control, thus less able to respond to sudden changes in demand for electricity, wind energy is less suitable. This is the case of France and its nuclear reactors .

Moreover, all countries do not enjoy the same wind potential. In the future, technological innovations, the development of intelligent networks and electricity storage solutions could also change the situation.

Offshore wind farms

New technologies for offshore wind are the most promising today. Indeed, some countries such as Denmark are already saturated onshore wind turbines. Others can impose new locations for their citizens because of the negative image that the public can make wind turbines. Build these wind turbines offshore, where winds are stronger and more constant, meets both societal demands and energy requirements.