Three blades, and each one is a wing
How Does a Wind Turbine Work?
A wind turbine blade does not get pushed by the wind. It gets lifted by it, like an aeroplane wing.
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Step 1 of 5
The blades are lifted, not shoved.
Each blade has the curved cross-section of an aircraft wing. Air moving past it produces a force sideways, and since the blade is fixed to a hub, sideways means round.
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Step 2 of 5
Twice the wind is eight times the power.
Doubling the wind speed brings twice as much air, each parcel moving twice as fast and carrying four times the energy. That is why turbines are put in the windiest places available.
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Step 3 of 5
Slow blades are moving very fast.
The tips look lazy at fifteen turns a minute, but a blade can be eighty metres long, so the tip travels faster than a car on a motorway. Gearing takes that up to generator speed.
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Step 4 of 5
It turns to face the wind and tilts to spill it.
A vane on the roof tells the machine which way the wind is coming from, and a motor swings the whole head round. In a gale the blades twist edge-on so the storm slides past.
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Step 5 of 5
No turbine can take all the wind.
If a blade stopped the air completely, no more air could get through. The air has to keep moving, so about three-fifths of the wind's energy must be left in it — a limit no design can beat.
Three blades is a compromise: two is cheaper but shakes as it turns, and four costs more without catching much extra.
The short version
A wind turbine's blades are wings lifted sideways by moving air — and no turbine can take more than about two-fifths of the wind's energy.
Try it yourself
Hold a spoon's curved back into a running tap. It pulls sideways into the flow rather than being pushed away. That is the same lift.
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