Blowin' in the wind: solution

March 2008

Blowin' in the wind: solution

In last issue's Outer space we developed a formula for the power output per unit time of a windmill: where is the speed of the approaching wind. We deduced that an average wind speed of gives a power output approximately equal to 0.38. The question was why this calculation significantly underestimates the true output.
The answer lies in understanding that the average speed is not a good guide. If, for example, the wind speed was for half of the time unit and 0 for the other half, then we would get an output approximately equal to This is four times more than what we got in the original calculation.
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