Wind turbine

From ArticleWorld

A wind turbine is a machine that converts energy possessed by the wind into mechanical energy, which in turn is used to run machinery such as pumps or electric generators. The force exerted by the wind acts on oblique blades that are mounted on a rotary shaft.

Working and uses of wind turbines

Modern wind turbines consist of a mechanism by which wind pushes a set of blades, thus causing friction as well as lift. Turbines which are propelled by lift, the same phenomenon which occurs in aircraft taking off, tend to be far more efficient.

Modern wind turbines can be of two types:

• Horizontal-axis machines, with their main shafts parallel to the ground on which they are installed.
• Vertical axis machines have shafts that are at right angles to the ground.

While horizontal axis turbines are used for generating electricity, vertical axis turbines are used for pumping purposes. The wheel in both cases is used to turn gears. When the wind velocity exceeds a certain limit, the rotors are decoupled to prevent damage to the rotating mechanism.

Wind turbine generators use rotors, a gearbox to raise speed of the rotary mechanism and a generator. The pitch of the blades can be altered to adjust speeds of the blades. Modern machines involve minimum speeds of less than 20km/hr and can generate to their rated capacity of a few hundred kilowatts at speeds of up to 50km/hr. Wind speeds up to 100km/hr are not allowed and systems are shut off. Windmill farms can generate power up to over a thousand megawatts, sometimes comparable to the generating capacity of a typical nuclear plant.

History and development of wind turbines

Wind energy has been known to be used for grain-milling and irrigation purposes as early as the 7th century A.D. Vertical shaft machines were used in many places across China and the Middle East. Harnessing of wind energy earned popularity in countries like France and England during the Middle Ages. Before gradual improvements were made to the design of windmills, most machines of that age consisted of wooden structures and were very inefficient.

Modern wind turbine systems in water-pumping and electricity applications are gaining importance in rural regions across the globe. Scientists predict that 10% of the world's electricity supplies may be met by wind turbines by the middle of this century. Running costs are very low in such systems. Pollution is almost out of the question; thus making it a good alternative to non-renewable fuels like oil and natural gas.