As you probably know, tripling wind speed produces 27-times more electrical power.

That’s only half the story. Air density is the invisible, intangible and often overlooked factor that leads to large wind energy estimation errors. Air density is the second most important factor of the wind energy equation. When air density is doubled, our wind power output is doubled.

Factors effecting air density are:

• Air temperature.

• Elevation (height above sea level).

• Air humidity.

• Air pressure from changes in weather.

So how easily can air density change?

• Between winter and summer, a 27 °C degree swing in air temperature alone, leads to 10 % loss of wind power.

• A 60 % drop in humidity between a humid day and a dry day of similar temperature will lead to a 1 % gain in wind power due to a 1 % increase in air density.

• A high pressure weather front after a depressive low pressure drizzle can lead to a 5 % increase in electrical production just due to the air density change.

• It is important to understand that air density effects can lead to higher errors in wind power estimation than anemometer error alone. Obtaining accurate air temperature readings with a very good solar radiation shield to prevent solar heating errors is very important to avoid false air density changes from inaccurate air temperature.

One can clearly see that even the most accurate anemometer alone is not enough to make reliable and accurate wind power predictions. We must also measure air temperature, pressure and humidity to get a complete picture of the atmosphere to make accurate wind energy predictions.

Take a peek at our air density calculator to get a feel how a hot humid summer day can effect your wind energy output: Air Density Calculator

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