**2. Overview of wind energy technology**

Wind energy is the indirect form of solar energy which is always being replenished by the sun. The differential heating of the earth's surface by the sun causes wind. It has been estimated that about 10 million MW of energy are continuously available in the earth's wind [6–8]. Wind energy could act as an environmental friendly alternative and national energy security especially during times of limited global reserves of fossil fuels, which threatens the long-term sustainability of global economy.

The technology of wind turbine has a technical identity and demand that is unique in terms of the design methods. Recently, remarkable advances and improved reliability in wind power design have been achieved owing to developments in modern technology. The structural dynamics advances and aerodynamics along with micrometeorology since 1980, have led to about 5% increase annually in wind turbines energy yield [9–13]. Present science and engineering research methods are producing better, stronger, lighter and more efficient blades for wind turbines. Wind turbines annual energy output has increased enormously and the weights, emitted noise of the wind turbine during operation have been halved over the last few years. A considerable amount of power can be obtained from wind energy technology by establishing more wind monitoring stations, effective selection of wind farm site with proper wind generator, enhanced maintenance procedures and practices of wind turbines, increase the wind generator availability, the use of large capacity wind generator, low wind regime turbine, higher heights of tower, wider rotor blade swept area, improved structural design and aerodynamics, proficient and enhanced technique for computer-based machining, improved power factor and better policies of the government.

Wind power generation has an edge over the other renewable energy technologies application, because of its technological maturity, good infrastructure and relative cost competitiveness. In the near future, wind energy is expected to play a vital role in both national and international levels regarding energy scenarios [1, 5, 14]. Basically the kinetic energy of the wind is converted to electrical energy via the wind turbine blades rotation. According to Greenpeace report in the literature, by the year 2020, about 10% electricity in the world can be obtained by the wind energy. However, wind power is already competitive with conventional fossil fuel power stations at good windy sites. With this enhanced and mature wind technology, together with superior economics, experts predict wind power would capture 5% of the world energy market by 2020. Advanced wind turbines must be more reliable, efficient, robust and less expensive than current wind turbines.
