During the past 40 years, wind power has grown into a major international industry [1–3], having 670,000 people employed worldwide in 2011 [4] and roughly 225,000 wind turbines operating at the end of 2012 [5].
During the past 40 years, wind power has grown into a majorinternational industry [1–3], having 670,000 people employedworldwide in 2011 [4] and roughly 225,000 wind turbines operatingat the end of 2012 [5].