Windmill Efficiency

A Commercial Wind turbine
Windmill Equation


There are some commercial wind turbines on the market, intended for the homeowner, including one advertised as a 1000-watt unit.  The company provides the actual characteristics of the wind turbine in a slick brochure, with a line representing best-possible conditions and a shaded area of lower power to hedge their bets.

The theoretical upper limit to the efficiency of a wind machine (of any kind) is 59%.

The equation below shows the power that can be expected from a top-notch windmill, operating at an efficiency of 50%. 

The graph below shows the power versus velocity with several different lines: 

The power in the wind

The power that could be extracted at 59% efficiency

The power that could be extracted at 50% efficiency (that is, if the wind turbine were good enough to be considered excellent)

The actual power output from the wind turbine.

The lout, who runs the wind turbine factory says (about efficiency) "So is this a negative? Does it really matter?"

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