Introduction

With a capacity that has tripled in the last 5 years, wind energy is again the fastest growing energy source in the world. Wind turbines (WTs) are used to collect kinetic energy and to convert it into electricity. The average power output of a WT unit has increased signiŽ- cantly in the last few years. Most major manufacturers have developed large turbines that produce 1.5-5.0 MW of power for onshore applications and are thinking of bigger units for offshore projects. Grouped together, they generate energy equaling 2% of the global electricity consumption, with about 200 GW of wind-powered generators worldwide by the end of 2010.