Wind energy is the kinetic energy of moving air masses around the globe. The etymological root of the term “Aeolian” 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 causes differences in temperature and pressure. As a result, the air masses move and accumulate kinetic energy. This one can be transformed and used for several purposes:
- Transformation into mechanical energy: the wind is used to drive a vehicle (sailboat or sand yacht), to pump water (pumping wind turbines to irrigate or water livestock) or to spin a millstone ;
- The production of electrical energy: the wind turbine is coupled to an electric generator to manufacture direct or alternating current. The generator is connected to an electrical network or operates within an “autonomous” system with an auxiliary generator (for example a generator), a battery bank or another energy storage device. A wind turbine is sometimes referred to as an aerogenerator when it produces electricity.
Wind energy is a renewable energy that does not directly produce greenhouse gases during the operation phase.
Modes of exploitation of wind energy
- Onshore wind turbines are installed on land.
- “Offshore” wind turbines are installed at sea.
There are two types of installations:
- industrial: large wind farms (or “wind farms”) connected to the electricity grid;
- domestic: small wind turbines installed at private homes.
Technical or scientific functioning
The process of converting 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, the speed of the wind and finally the temperature which influences the density of the air.
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.
The maximum recoverable power (P) is given by Betz’s law: P = 0.37. S. V 3; where 0.37 is the constancy of air at standard atmospheric pressure (1013 hPa), S the swept area, and V the wind speed.
In practice, a wind turbine produces four times more energy if the blade is twice as big and eight times more energy if the wind speed doubles. The density of the air also comes into play: a wind turbine produces 3% more electricity if, for the same wind speed, the air is colder than 10 ° C. Wind power depends mainly on the intensity of the wind and its variations. Wind energy is, therefore, intermittent and random energy.
The wind is stronger and more constant at sea. The wind turbines installed there are also more powerful.
The blade/rotor assembly is facing the wind by a rudder system. Most wind turbines start when the wind speed reaches about 3 m / s and stop when this speed reaches 25 m / s. Generally, wind turbines are parameterized to make the best use of intermediate power winds.
Challenges with energy
Considered as clean energy, wind energy is booming. Among renewable energies, it is regarded as a mature technology and the most economical after hydropower.
According to the Global Wind Energy Council (GWEC) (1), the installed capacity of the global wind farm more than doubled between the end of 2010 and the end of 2015. At that date, it reached almost 432.4 GW. Despite this growth, its share of total global electricity production remains limited at around 3%.
Beyond economic and environmental factors, wind energy is of particular interest because it can contribute to the diversification of electricity mix and energy independence of countries. This source of energy is thus often at the heart of strategies for the development of new electrical capacities, despite the limits that it may present: its randomness, its efficiency and its intrusion into natural landscapes that can be poorly accepted by local residents.residents.
The advantages of wind energy
- Wind energy is renewable and “decarbonated” during the exploitation phase.
- The land where the wind turbines are installed is still exploitable for industrial and agricultural activities. The installation can be dismantled relatively easily.
- Their offshore development has significant potential.
- Locally located, wind turbines can be used to meet mass electrical needs as well as limited domestic needs, depending on their size.
The problems that arise
- Wind energy depends on the power and regularity of the wind.
- It is an intermittent source of energy.
- Development zones are limited.
- Wind turbines can trigger environmental conflicts of use, such as visual and noise nuisances.
- There may be conflicts over the use of land or sea space with other users (e.g., fishermen, boaters).
Countries with the largest wind capacities
China and the United States have the largest wind farms in the world, with 145.1 GW and 74.5 GW respectively installed at the end of 2015. Then follows Germany, the European leader in wind energy (and worldwide until 2009) with 44.9 GW installed. If one compares the wind capacities to the area and the population of the leading countries developing this sector, Denmark is on the other hand in the first place.
Europe has long dominated the global wind energy market but now has a wind farm equivalent to China’s installed capacity.
In France, around 1 GW of wind is connected each year to the electricity grid (10.3 GW of installed capacity at the end of 2015).
Wind energy companies
According to Make Consulting, the top 5 wind turbine manufacturers in 2014 were:
- Siemens (Germany) with 10.8% global market share;
- GE Wind (United States) with 10.2%;
- Vestas (Denmark) with 10.1%;
- Goldwind (China) with 9.2%;
- Enercon (Germany) with 7.8%.
Units of measurement and key figures
On average, a French person consumes 7,382 kWh (total electricity consumption relative to the population), an American 12,987 kWh while a Beninese consumes only 94 kWh. By way of comparison, a 2 MW wind turbine installed in France produces an average of 4 million kWh per year, according to the load factor of the French wind farm (23 %, which corresponds to a full-scale operation of a just over 2,000 hours a year, or 6 hours a day).
In France, the wind sector represents 12,520 direct jobs at the end of 2014.
At the end of 2015, the installed capacity of the European wind farm reached 142 GW, including 11 GW offshore (mainly in the United Kingdom, according to EWEA (European Wind Energy Association), which would generate around 315 TWh per year, which assumes an average load factor of about 25.3%.
At the World level
In 2015, nearly 63 GW of new wind capacity was installed worldwide. Wind power would have produced almost 706 TWh in 2014 or about 3% of the total electricity production in the world.