Wind energy

Wind energy it has been modified: 2012-09-25 di Enrica Garuglieri

In the world, 80% of the energy used is produced by burning fossil fuels, including oil, coal, methane. 
Plants that use fossil fuels generate polluting gases that damage the environment. In recent years, to protect the environment and to compensate for the growing demand for energy, states around the world have committed themselves to pursuing a model of sustainable development, including the exploitation of kinetic energy produced by wind.
The need to find alternative sources of energy spread following the 1973 economic crisis, when the Arab countries raised the price of oil which caused, among other things, the increase in the price of electricity, consequently increased among the States the awareness of the exhaustion of fossil fuels and therefore the need to seek alternative and renewable resources.
By way of example, an onshore wind farm consisting of 30 wind turbines of 300 kW each in an area where the wind blows at a speed of about 25 km / h can produce 20 million kWh per year, or the requirement of about 7000. families. To achieve the same result, a coal plant would release 22 tons of carbon dioxide, 125 tons of sulfur dioxide and 43 tons of nitrogen oxide into the air.

The first use of wind energy occurred in prehistoric times through the use of naval propulsion in the sails of boats and ships.
The first windmills appeared in Persia and Mesopotamia around the II-III millennium BC, in which wind energy was used to transport water or to move millstones and grind cereals.
In Holland, wind energy was used to pump water from the polders (parts of land below sea level). These mills were formed by wooden frames on which the canvas was fixed which in this way formed sails pushed in rotation by the wind. 
Recently wind energy is exploited by means of impellers to be transformed into electricity. 

There are two types of wind farms: onshore plants which are wind farms located on land and offshore plants which are plants installed a few miles from the coast of seas or lakes, to make the most of the strong exposure to currents in these areas.
There are also off-grid wind farms, in other words independent wind farms, used in the production of electricity for self-consumption. They are not connected to the national electricity grid, as they are designed to fully satisfy individual energy needs. These systems are especially ideal for those who live in mountain huts or in particularly windy regions. Those who install off-grid wind farms are free from the cost of energy bills.
The distance between the wind turbines is calculated to avoid mutual interference, they must be located at least 5 or 10 times the diameter of the blades. To determine where to install a wind power plant, you need to know:

  • The conformation of the land, which influences the wind speed and must belong to a low roughness class and have a slope between 6 and 16 degrees; 
  • The direction and speed of the wind. The direction can be classified on the basis of geographical origin or the "Rose of the winds". The force can be indicated either with the measurement of its speed (knots) or through the scale proposed by Beufort. Modern windmills are called wind turbines. The rotational movement of the blades produced by the wind is transmitted to a generator that produces electricity.

Modern windmills are called wind turbines. The rotational movement of the blades produced by the wind is transmitted to a generator that produces electricity.
There are several models of wind turbines in shape and size, the most used are of medium size wind turbines: 50 meters in height, with two or three blades of 20 meters, is capable of providing a power of 500 / 600 kW and satisfies the need electricity 500 family around.

The wind turbine consists of:

  • The rotor consists of a hub on which the blades are fixed (often glass fiber) that can rotate at a higher speed than 200 km / h;
  • the driving system. The wind turbine is equipped with an aerodynamic braking system which is used as an emergency brake to stop the rotor in case of wind overspeed and a mechanical braking system, used to complete the stopping of the rotor and as a parking brake;
  • The tower and the foundations. The tower is built in reinforced concrete wood, steel or synthetic fibers in a tubular shape and its task is to support the nacelle and the rotor. The foundations, through which the tower is anchored to the ground, are usually in reinforced concrete;
  • The spin multiplier. Its purpose is to transform the slow rotation of the blades into a faster one for the electricity generator to work;
  • The generator. It transforms mechanical energy into electrical energy;
  • The control system. It has two functions: to manage the wind turbine in its various working functions and activate the safety device which, in case of malfunction and overload due to an excess of wind speed, blocks the operation of the wind turbine;
  • The spacecraft and the yaw system. The nacelle is a cabin in which all the components of the wind turbine are placed, it is arranged on the top of the tower and is able to rotate 180 ° on its axis. The yaw system is a servomechanism that ensures continuous alignment between the rotor axis and the wind direction. In case of deviation of the axis of the wind direction, the vane activates a motor that realigns the nacelle.


At the end of 2011, the global generation capacity of wind turbines was 237 gigawatts; the overall potential production, estimated at about 500 terawatt hours, is equal to about 3% of the electricity consumed in the world. 
The first place in the world for installed power is China with 62 gigawatts of installed power, followed by the United States of America (47) and Germany (29).
In Italy the first wind turbines were installed in 1990, but only since 1996 has there been a significant number of plants connected to the electricity distribution network. The contribution of renewable sources in Italy is 7,4%.
The regions most affected are those of the south, in particular Campania, Puglia, Molise, Sicily and Sardinia.

The advantages of renewable energy, particularly wind power are:

  • The use of an energy source, wind, which is renewable, sustainable, inexhaustible and with a low environmental impact;
  • No ground gas CO is produced2 , Except in small quantities for the construction of the plant;
  • The dimensions of the wind farms are suitable to meet the needs of small cities or sparsely populated provinces, as they are easily scalable in power;
  • The costs of maintenance and dismantling are very low as many components are recyclable and reusable.
  • There is room for improvement in cost, in the transformation of the current mechanical and electrical current to storage through the use of batteries.

There are some side effects of the plant:

  • The occupation of the territory. The wind turbines and the supporting works occupy only 2-3% of the territory necessary for the construction of the plant (the remaining part of the territory can be used for agriculture and pastoralism).
  • Visual impact. Due to their configuration, the wind turbines are visible and in some cases disfigure the surrounding landscape
  • Noise. The noise emitted by a wind turbine is caused by the friction of the blades with the air and by the speed multiplier. The noise from a wind turbine must be less than 45 decibels near homes
  • Effects on flora and fauna. The only effects observed are the impact of birds with the rotor of the machines.
  • Interference on telecommunications and electromagnetic effects. The activity of the wind turbines can interfere with the activity of the radar.
  • In conclusion, the advantages of wind farms to protect the environment and the welfare of the individual are qualitatively outweigh the disadvantages, which can be alleviated with small steps, such as the form carefully choose the color and size of the wind turbines because they harmonize with the landscape.

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