The aim is to be able to explain to children what forces the wind exerts on those blades. To explain this simply, I propose to remove the blades and make the rotor move with a chain that turns on a gear at the bottom of the windmill, like on a bicycle. Plates are then attached to the chain on which weights can be placed. At the top they are placed on top and when the other comes on the chain, they fall off again. Suppose the windmill is 100 m high and we attach a plate to the chain every 10 meters on which a weight can be placed, what is the necessary weight to make the windmill turn as normally happens by the average wind?
Answer
Dear Marc,
the most oversized windmills (which are placed in the sea) expect a torque on their generator about 2500kNm. If you know that a sturdy vehicle delivers a torque of less than 1 kNm, you can already form a picture of the power…
To work with your equation, some physics will suffice: suppose the drive shaft (for simplicity’s sake) has a radius of 1m. Then a force of 2500 kN must act on it, which corresponds to 250 tons. If you then have a chain of 100 m with a plate every 10 m, you can put 10 weights of 25 tons each (a heavy truck) on the plates.
Answered by
ir. Bart De Schouwer
For my position I am the manager of a group of engineers who maintain production equipment. It is mainly with my ready knowledge (education, interests, …) that I could answer questions.
Kapeldreef 75 3001 Leuven
http://www.imec-int.com
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