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The difficulty in answering this question is compounded by the difficulty in obtaining accurate data to make energy production assumptions. Below is our attempt to simplify the answer. Though we can almost identify maximum capabilities it is difficult to accurately estimate wind speeds, consistency and conversion capabilities of the equipment being used.

The primary fixed attribute in wind power production is a fixed standard based on Betz's Law. In 1919, a German physicist named Albert Betz determined that a wind turbine cannot convert more than 59.6% of the energy in the wind to mechanical or electrical energy. The reason for this is that wind turbines extract energy from the wind by slowing the wind. For a turbine to be 100% efficient it would have to reduce the wind velocity to zero. If you were to stop the wind there would be no wind to turn the rotor. However, this law can be manipulated and miss-understood. Betz's law was specific to direct inflow and outflow of a "Single" current/flow of motion. the real world doesn't always present direct single flow currents, therefore this law is not wrong but not applied well to turbulent wind conditions whereas smaller wind devices at times can experience power conversion greater than 59%. link to blog on subject

  1. Wind consistency is another primary attribute to calculate wind production. Though everyone experiences "good" wind from time to time, the "quality" of wind might not be applicable for wind power generation. One of the primary barriers in converting wind energy is the rapid changes due to wind "gusts" associated with most wind conditions. Gusts are often misidentified as constant wind or "good" wind conditions. Gusts cause the turbine generator to rapidly speed up and slow down, this rapid change in motor RPM makes the conversion of energy difficult to capture.

    You can calculate average wind speed over the course of a day or a week with a handheld electronic anemometer, taking readings periodically and then averaging them. For greater accuracy you need to know the consistency of the wind to warrant installing any wind turbines. A fixed data logging anemometer over a longer period of time is an ideal solution.

    What you are looking for is "Constant" wind conditions. Periods of time when you get good solid winds with little changes in speed. This is a great indicator of "good" wind.

  2. Power projection based on real-time Constant Wind and Annual Wind Conditions at the indicated specific wind speed.

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    A great first look tool for wind conditions in your local area is Wunderground. http://www.wunderground.com Drill down to your local area and then click on any dot/flag on the area map. Click on the top right link - "station name" to expand the data available. Most data includes detailed Annual Wind conditions.

    The following table provides a power curve as applied to Anual Average Wind Conditions. It is important to understand that "Average" annual winds at any indicated speed were determined from wind conditions that could have been substantially greater than the "Average" wind indicated in the table. Acutal Wind to Power "real-time" production is less than indicated in this table.

  3. Equipment efficiency is the final factor. Similar to Solar, only so much energy can be effectively transferred and converted. Due to the nature of wind, rapid changing conditions, modern equipment isn't capable of adjusting fast enough to convert or lock onto the energy being generated for conversion. For more information on these barriers Click Here.

The formula for calculating the power from a wind turbine is:
Calculation for Wind energyWhere:
P = Power output, kilowatts
Cp = Maximum power coefficient, ranging from 0.25 to 0.45, dimension less (theoretical maximum = 0.59)
ρ = Air density, lb/ft3
A = Rotor swept area, ft2 or π D2/4 (D is the rotor diameter in ft, π = 3.1416)
V = Wind speed, mph
k = 0.000133  A constant to yield power in kilowatts. (Multiplying the above kilowatt answer by 1.340 converts it to horse- power [i.e., 1 kW = 1.340 horsepower]).

The rotor swept area, A, is important because the rotor is the part of the turbine that captures the wind energy. So, the larger the rotor, the more energy it can capture.
Air Density
The air density, ρ, changes slightly with air temperature and with elevation. The ratings for wind turbines are based on standard conditions of 59° F (15° C) at sea level. A density correction should be made for higher elevations as shown in the Air Density Change with Elevation graph.
Although the calculation of wind power illustrates important features about wind turbines, the best measure of wind turbine performance is annual energy output. The difference between power and energy is that power (kilowatts [kW]) is the rate at which electricity is consumed, while energy (kilowatt-hours [kWh]) is the quantity consumed. An estimate of the annual energy output from your wind turbine, kWh/year, is the best way to determine whether a particular wind turbine and tower will produce enough electricity to meet your needs.
 

 

  
 
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