Since the industrial revolution of the middle of the 18th century, and more particularly since 1950, human activity has caused an exponential increase in the emission of greenhouse gases into the atmosphere. This has contributed to the deregulation of the natural phenomenon of the greenhouse effect and resulted in an increase of the average temperature in the atmosphere, and global warming.

Moreover, our consumption of energy rests on limited resources. If we continue to consume like we do today, there are likely to be soon a shortage of oil and gas, which will be accompanied by increasingly high prices for these resources.

In this context we have decided to work on a project that will reduce C02 emissions and consequently use removable energy. This is the harnessing of wind power.

The modern aero-generators, called windmills, have profited from technological advancements since a few years. They are reliable and effective and allow a decentralized electric production, without pollution, or gas emission with greenhouse effect. Their installation involves a dialogue with the populations involved and affected by these projects.

How is it done?
A wind mill is a huge contraption; it is a large-sized machine, perched very high. This high size is the result of the technological advances achieved in the ten last years in order to improve the electric output and competitiveness of the wind mills.

A wind mill includes the following elements:
- a massive reinforced concrete base,
- a mast containing the equipment such as the transformers, - a nacelle ensuring mechanical/electric conversion, - and finally a rotor and the blades

How does it work?

• 1/ The rotation of the blades:
Under the effect of the wind, the propeller, also called rotor, is started. Its blades turn.
The rotor is located at the end of a mast because the winds blow stronger at higher altitudes. According to the type of wind mills, the mast can vary between 10 and 100 m in height.
The rotor comprises of 3 blades, measuring between 5 and 90 m in diameter.

• 2/ Electrical production:
The propeller involves an axis in the nacelle, called tree, connected to an alternator.
Thanks to the energy provided by the rotation of the axis, the alternator produces an alternating electric current.

• 3/ The adaptation of the tension:
A transformer located inside the mast raises the tension of the electric current produced by the alternator so that it can be more easily transported. To be able to start, a wind mill requires a minimal speed of wind from approximately 10 to 15 km/h. For questions of security, the wind mill automatically stops functioning when the wind exceeds 90 km/h. Optimal speed is of 50 km/h.

Some interesting statistics

An average modern wind mills  have the following characteristics:
- Height of the nacelle: 80 m
- Diameter of the rotor: 70 m
- Diameter of the mast: 4 m
- Total mass: 300 tons
- Nominal output: 2 MW (2 million Watts)

Contributed by Francois Le Naoures, SUP 3, ISEG