Over the years, wind turbines have gotten tall with long, thin blades. This MinutePhysics video delves into the reasons for those changes. They’re all aimed at generating more wind power and doing so with greater efficiency.
I’ll add one caveat to the video, though, because you may wonder how modern wind turbines can be fast when they appear to rotate so slowly. That’s a trick of the reference frame. The power a turbine blade generates depends on the flow speed over it, and the relative air speed is greatest near the tip of the turbine blades.
Think of the circle the blade tip traces. For a given rotation rate – say once revolution a minute – the blade tip has a much larger distance to travel than the blade’s base does. Divide that large distance by the rotation time and you get a large velocity. So even though the wind turbine appears to be rotating slowly, the flow the blade sees is quite fast. And the longer the wind turbine’s blades, the larger this effect. (Image and video credit: H. Reich/MinutePhysics)