Wind is basically the movement of air, which depends on the sun. Solar heating patterns on the surface of the earth create this phenomenon. Different land and water bodies on our planet's surface absorb the sun's heat at varied rates at different times of the day; for e.g. during the day, the air over land surfaces heat faster than over water. On expanding, this warm air rises with cooler, denser air replacing it, creating a movement known as wind. During the night we see the reverse of this pattern. Geographical location, vegetation density and the intensity of solar heat are also some of contributors in wind creation. When in motion, the air has copious amounts of resulting energy that can be gainfully used in various forms and for various purposes.
Thus the wind is not only something pleasant you look forward to on a balmy day, but can be one of the most effective forms of energy creation, when harnessed correctly. Since it depends on the sun, wind power or energy is a renewable and 'green' way to power our world. It can be used to create or supplement electricity and mechanical power.
The vital cog in the process of wind energy usage and creation for the generation of power, are the Wind Turbines. These turbines employ the mechanics of a reverse fan. Powered by the wind's energy, its blades help in generating electricity. The basic mechanics consist of the turbine's blades that are put into motion by the wind, and are connected to generators. Finally, these generators are used to transform this rotational energy into electric power.
How they work:
Turbines typically have two or three blades. Even in a wind-less situation, the blades on a wind turbine are positioned at an angle of 45 degrees so that the turbine can trap all possible energy even with the slightest of winds. When in contact with the wind, the fronts of the rotor blades (which have the larger surface area) propel to a 0 degree angle and are bombarded with energy, from the front and the back. In essence, this creates positive pressure on the fronts of the blades and negative pressure behind them, causing a suction type effect which in turns lifts the blades and transfers the wind energy to kinetic energy. This force turns the shaft connected to the rotors, creating a strong rotational energy which gets converted to electric energy by the generators.
An electric control system connects the generator. The entire system channels the produced electric energy to high voltage transformers and eventually the grid. These grids are responsible for supplying energy to places like homes, farms, factories, water pumps, as well as commercial power suppliers.
The efficiency of wind turbines depends on various factors such as location, geographical factors, mechanics, rotor shape/size, etc... Output can be regulated by a constant or variable rotational speed, as well as adjustable and non-adjustable blades. This control is essential because sometimes the wind's speed puts too much stress on the turbine, causing safety controls to kick-in and apply brakes to the rotor to prevent it from damage.
Types of Wind Turbines:
Wind turbines can be classified into two major types. Although they work on the same basic premise, the process and design differ greatly.
Horizontal Axis Wind Turbine (HAWT): Horizontal axis wind turbines are more widely used and are the more traditional style in turbine design, mostly seen in wind farms. These are generally used to power electrical generators, because of the usage of gearboxes which enable change in rotation speed. Efficiency of a HAWT is generally high because of the angles the blades are set at, a blade pitch that is adjustable and the height of the tower (as greater wind speeds are found higher up from the ground, higher towers typically capture more wind energy). A horizontal turbine therefore is mainly run by a system of blades/rotors, a generator, a gearbox, the shaft and a supporting tower.
Vertical Axis Wind Turbine (VAWT): Vertical axis wind turbines, as the name suggests, consist of a vertically arranged rotor shaft. This is also known as the 'egg beater' style. A vertical axis wind turbine has proven to be very useful at locations where the wind direction tends to vary. This type of turbine however, is said to be not as reliable and efficient as a HAWT, one of the reasons being the low placement of the rotors.
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