wind energy


#1 History of wind energy

Wind energy is one of the oldest sources of energy used. Its use in the past was widespread in the production of mechanical energy (pumping water, grain grinding as well as sawing of wood, etc..)
At that time, these windmills (aero motors) were economically profitable and they have contributed to the economic development of Europe.

From the 19th century, these applications began to lose their interest. It is because of the technological evolution that Europe has known.

read also : history of windmills

#2 Wind Energy: What is it?

To obtain wind power, mechanical power is created with the kinetic energy of wind. A generator converts this power into electricity so that it can be used for human benefit. Recently, different types of electricity generation have been a frequent topic of debate amongst experts.
Wind energy is certainly one of the cutting edges of technological breakthroughs that could lead to more efficient energy production. The future of wind energy appears promising, at a glance. That may be the case, but some disadvantages are also to be considered.

#3 Power Generated by Wind Turbines


Wind energy is highly diluted and needs about 8 ha for 1 MW installed, running about 20% of the time. A giant wind turbine can reach a peak power of 2 MW (50 m in diameter). In France, the potential is estimated at 66 TWh / year on land or 7.5 GW average, and 97 TWh / year offshore or 11 GW average. This would make up 30% of the electrical output. Therefore it would be necessary to install at least 30,000 wind turbines in order to produce just 5 percent of French electricity, i.e. to generate continuous power of 10 GW.
One wind turbine per 50 m will mean a 1,500 km long wind turbine continuous curtain. The erratic and fairly unpredictable nature of the wind makes matching with the wind turbine network difficult.A parallel development is needed to overcome windless times. Storage means such as hydrogen should be built to make this mode of production more appealing in the future.

#4 How do wind-turbine work?

Wind turbines run on a simple principle: using wind to generate electricity.
The wind spins a revolving engine’s propeller-like blades around a rotor, spinning a generator, generating electricity. The wind could be a kind of alternative energy arising from a combination of three synchronous events:

  • The sun erratically heating the atmosphere
  • Irregularities of the layer
  • The rotation of the planet. 

Wind velocity patterns and velocities vary greatly across us, and square measurements are modified by water bodies, trees, and tract variations. For several purposes, humans use this wind flow or motion energy: sailing, flying a kite, and even electricity generation.

A turbine turns wind energy into electricity-victimizing the rotor blade force that works as an Aircraft Wing Associate in Nursing or Aircraft Control Surface. The gas pressure on one facet of the blade decreases once the wind flows through the blade.

The difference of gas pressure across the blade’s 2 sides lifts and drags each. The raise force is greater than the drag, resulting in the rotor spinning.
The rotor connects to the generator either directly (if it is an instant drive turbine) or through a shaft and a series of gears (a gearbox) that accelerate the rotation and allow a physically smaller generator to operate.

#5 Wind energy can be used in two ways

  • Conservation of mechanical energy: wind is used to drive a vehicle (Sailing vessel or sand yachting), to pump water (Mallorcan mills, wind turbines pumping to irrigate or water livestock), or to turn the millstone.
  • Transformation into electrical energy: the wind turbine is coupled to an electric generator.

To make direct or alternating current, the generator is connected to an electrical network or works independently with a backup generator (for example a generator) and/or a battery bank or other energy storage device.

#6 Classification of wind turbines

Wind turbines are generally classified according to the axis of rotation:

I. Horizontal axis Wind turbines (HAWT)


Most modern wind turbines use this principle, with a number of blades variant. They are distinguished by the number of their blades: quadruple, three-bladed, two-bladed, …
there are even monopoles (with a counterweight).
Among this category, there are:

Slow wind turbines



This type of wind turbine has a large number of blades, this obviously facilitates the starting thanks to its high torque. But this is a disadvantage when the speed increases due to vibrations. These wind turbines cannot reach high speeds.
These wind turbines are used as wind turbines, in particular for pumping.


In contrast, to slow wind turbines, fast wind turbines (single-blade, b-blade, and the three blades) must sometimes be launched by an electric motor; however, once launched, they return the energy consumed at startup.

If the wind speed is high the vibrations are too strong and may break the blades, for this the wind turbine is braked then stopped at a speed of the order of 20 to 25 m / s. These fast wind turbines are better suited for power generation.

It is this type of wind turbine which is the subject of this work, and whose objective is the study of the propeller from the dynamic and aerodynamic point of view.

II.Vertical-axis Wind Turbines (VAWT)


This type of wind turbine is characterized by its vertical axis. It uses the omnidirectional operating principle, which has the advantage of picking up the winds wherever they come from, without the need for an orientation mechanism. Another advantage in this type of wind turbine is the size of the blades, which is not as restrictive, compared to that of the type with a horizontal axis. Several models of vertical axis wind turbines have been designed, but the two most famous models are those of Darrieus and Savonius. All models in this category remained at the prototype stage, as they are not profitable at present, but all show ingenuity.

With the bankruptcy of the last manufacturer, Flowing (USA), vertical axis wind turbines are practically no longer manufactured today, but they will make engineers dream for a long time because their simplicity is attractive.

#7 Economic and ecological aspects of wind energy

Wind energy is currently achieving the highest growth rate of any energy sector in the world. In ten years, this energy has achieved an average growth of 29% per year. It represented only 5000 MW in 1995, today the electricity produced by this sector on a global scale exceeds 60,000 MW.

It is currently the most highly rated energy source. Over the same period, the use of coal increased by only 2.5% / year, nuclear power by 1.8%, gas by 2.5%, and fuel oil by 1.7%. Table 1.1 gives more details on the development of different energetic sources.
The wind industry has likely taken off, thanks to the sophistication of growing wind technologies. Today a modern wind turbine produces, per year, 200 times more electricity than its equivalent 20 years ago.

These technological gains have translated into economic gains; the cost of kW has dropped remarkably thanks to advances in wind technologies. Wind power, which cost between 70 ¢ – 80 ¢ (US $) per kWh in the early 1980s, currently costs between 4 ¢ and 6 ¢ per kWh, a drop of about 90%. In some regions, wind power is cheaper than that produced by traditional sources.

The wind industry is probably the greatest success among the technologies renewable since its costs have now become competitive with other traditional sectors.
Thanks to technological improvements that have enabled cost reductions, this sector currently occupies an increasingly important part in the energy balance in many countries, and it now represents a global production of 60,000 MW.

This energy source also has the advantage of being ecologically very clean since a wind farm fleet does not emit pollutants or greenhouse gases and does not generate waste and carries only minor risks to the environment.

In Algeria  (My Country) for example, The achievements in the field of wind energy are very limited in comparison with current global developments in this area, which has reached very advanced objectives. The share of renewable energies in the energy balance national is very low since it represents only 0.02% of consumption of national electricity company.Advantages & Disadvantages

The benefits of wind energy are more obvious than the inconveniences.

The main advantages of wind energy

  • First and foremost, is an unlimited, free, renewable resource (The wind itself).
  •  Hight Economic value.
  • low maintenance costs.
  • The wind is a natural occurrence and harvesting kinetic energy of wind doesn’t affect currents or wind cycles in any way. 
  •  Clean, non-polluting way to generate electricity.

Major disadvantages

  • Constructing turbines and wind Facilities and equipment is extremely expensive.
  • Technology immaturity.
  • Offshore wind turbines produce more energy than onshore wind turbines but cost much more to establish.
  • Wind turbines may be dangerous to fly animals. Many birds and bats have been killed by collision with the rotating blades but this number is incomparable with other unnatural and man-made (buildings, cars, electric lines)  
  • Some wind turbines tend to generate a lot of noise (vertical and old wind turbines ) which can be repulsive.

Despite the negatives related to wind energy, it remains one of the important and clean sources that we can rely on to produce electricity and High energy costs can be tackled in part directly with technical advances that improve efficiency and energy production and lower device capital costs.

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