If wind turbine blades are so long and heavy, how is the wind able to rotate them?
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The reason for e shape: It’s called aspect ratio:
Basically, the wind pushes the blade, ok nice.
The problem is that wind is lazy and doesn’t want to push the blade.
So the wind will try to escape from doing any work. It cannot escape the blade by preceding it, or going behind it, (leading edge/trailing edge) as it would still draw air on the profile and do some work. It cannot escape toward the center of the rotor of course.
But it can escape at the tip, the wind will run toward the outer part of the rotor disc, to do this escape.
The longer the blade the more the win has to “run” to make its escape, the narrower (cord-wise) the blade is the less the wind perceive it has to “run” away from working.
A very high aspect ratio blade, is a blade that is very thin and long. This blade is the best to capture wind and prevent most of it to escape.
Aspect ratio is very very important at low speeds. The slower the speed the more time the wind has to escape. That’s why sailplanes have very high aspect ratio, aka thin long wings.
About how the blade is made: fiberglass is 3 time stronger than steel (for same volume) and it’s more than enough to hold the blade together. Actually, it’s so strong that the blade is still mostly hollow.
About loads, you just need the blade to stay one piece when standing still on the side position. That’s the bigger stress. Once you have wind the rotor spin and the centrifugal force will keep the blade straight, at that point the blade could even be made of rope and still do the job.
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