2.05 – Wind Turbines: Evolution, Basic Principles, and Classifications

Technologies for wind energy conversion have significantly advanced during the past few decades. As a result, the wind power industry is fast growing and wind energy is widely accepted as the renewable energy resource which can be exploited in a commercial scale today. This chapter starts with a description of this evolution of modern wind turbine technology. These developments in the wind power sector are characterized in terms of the growth in the cumulative installed capacity, increase in unit size, improvements in the system performance due to technological advances and cost competitiveness. Future growth of wind power under different policy scenarios is also briefly discussed. This is followed by a section discussing the basic physics behind the wind energy conversion where the power and torque characteristics of the wind rotor are introduced. The significance of dynamic matching between the rotor and interacting wind stream is explained through the relationship between the power coefficient and tip speed ratio. Finally, different classifications of the turbines are discussed giving emphasis to the horizontal axis and vertical axis options. The chapter concludes with performance curves of various wind turbine designs ranging from high solidity multi-bladed rotors used in wind pumps to the modern three bladed horizontal axis rotors used for electricity generation.