Aerodynamics in wind turbine technology

Wind is a source of energy which drives numerous natural cycles such as rainfall, pollination and many more. Winds flows due to temperature differences therefore normally wind flows from sea to land.  There are some historical apparatus (in early 1900s) which were build to harness wind energy to use for mankind. These were to use convert wind to mechanical power only. Later wind turbine technological research spikes in 1950s for and become matured for economical & social aspects of mankind. Now days, wind is used to harness energy in form of electrical power. Wind flow can be tapped in some geographical areas where its flow is continuous throughout the year. The turbine size and selection is based on average speed of wind, terrain, and distance from residential areas / cities. It is essential that power estimated to be generated throughout the year must have a electricity market to sell power and generate profit.   

A wind turbine consists of blades, hub, gearbox, generator, mechanical equipment, nacelle cover, tower & foundation and electrical control system. The blades are made of glass fibre, carbon fibre or wood-epoxy material. The tensile strength of blades is tested for maximum stress (1.5 times stress exerted by wind at geographical location). The wind is made to strike the blades mounted on the hub which faces wind direction and distorts/expand the flow area of wind. It can be understood by Bernoulli’s principle. By one-dimensional momentum analysis, we obtain that power converted is directly proportional to the cube of wind speed. There are some constants with this relation which depends on air density, area of the swept speed of turbine & limitations of Bernoulli’s theorem is applicable. The drag and lift of blades are controlled by controlling the angle of attack of wind. This control mechanism may be active or passive. Also in case of wind speed increases beyond cut-off limits (under stormy conditions), the blades are pitched in the direction of wind speed to protect blades and hub structure.