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Questions and comments can be directed to windscience@iastate.edu.
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Wind Power
Generation
As seen above, the generation of wind power (Watts) is proportional to several variables. These include the air density (kg/m3), the square of the blade length (m), and
the cube of the wind velocity (m/s). Therefore, if the wind velocity were to double, the power generated would be multiplied by eight! With the generation of power so dependent
on the velocity of wind, this makes wind forecasts quite important.
Additionally, the generation of power is quite dependent on the turbine being used. Not only is blade length a factor, but also so are the height of the turbine and the turbine's
efficiency. The velocity of wind increases with height above ground; so with a taller turbine, higher wind speeds are experienced. Additionally, with so many parts in motion in a
wind turbine, the efficiency of power generation isn't 100%. Each turbine has a rated capacity factor that must be incorporated into the power equation. With a greater capacity
factor, efficiency is increased, and more power can be generated.
Wind Turbine Data
Estimate Power Generation
To quickly estimate the potential power generation at your location, follow these steps:
- Convert wind speed to meters per second: If wind speed is reported in mph, multiply that number by 0.45. If reported in knots, multiply by 0.51.
- Extrapolate wind speed to turbine hub height: The standard height where wind is observed is at 10 m, a far cry from the typical turbine height of 80 m. To estimate
wind speeds at 80 m, take your new wind speed in m/s and multiply it by 1.35. This conversion uses a wind profile power law exponent of 0.143 for a neutral atmosphere.
- Calculate a potential power generation: Using the above equation, plug your estimated 80 m wind in for v, 41 m for r (blade length for a utility-scale wind turbine),
and 1 kg/m3 for ρ. Don't forget the 1/2 and π constants! This calculated value is in Watts, so divide by 1,000,000 to see your potential power generation
in MW.
- Keep in mind this is the wind's potential power generation. Wind turbines are about 30 to 40% efficient, so a realistic estimate of power generation would need to take this
efficiency into account. Additionally, power output reaches a limit that the electrical generator is capable of somewhere between 14 and 18 m/s, so wind speeds above this won't
generate more power.
Latest IEM plot of potential wind power generation (in MW) using a GE 1.5-MW extra-long extended model turbine. Click to enlarge.
Average Annual Wind Maps
Average 80 m wind over Iowa. Click to enlarge.
Average 80 m wind over the US. Click to enlarge.
Average 90 m offshore wind in the US. Click to enlarge.
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