For the purchase of a wind turbine to be economically feasible, a minimum wind speed of 4 m/s (9 km/h) is necessary. Though advances in wind turbine technology have created exceptions to the rule (see Top 5 Wind Turbines for Low Speed Wind Conditions) the fact remains that wind turbine output is based on the cube of wind speed, which means that if wind speed doubles, a turbine can produce eight times more power. Even a slight increase of 1 mph — from 11 to 12 mph — can yield a 33% increase in power. So before spending your hard-earned dollars on a funky monument for your backyard, know how much wind Mother Nature blessed you with before making the decision to buy.
Research wind speeds
Have a look at a wind atlas to determine your area’s average wind speed. Links to a few countries’ wind atlases are listed under Resources below. If your country is not listed, search wind energy resource atlas, plus the name of your country, on your favorite search engine.
Locate your specific region on the atlas to find out its average annual wind speed. Some atlases provide the speed in m/s or km/h whereas others provide a wind power class. On this 1 to 7 scale, class 3 and above is considered suitable for most wind turbines to generate power. Class 2 is marginal — wind power feasibility will depend on your turbine.
Though searching online for wind speed in your area is fast and simple, it is not overly accurate. These assessments are usually made at heights greater than a small wind turbine will be located at, meaning it will be able to access the stronger wind that comes with height and avoids the pitfalls of being sited close to the ground such as turbulence caused by trees and buildings and roughness of land (tall grass vs. water).
Test wind speeds
To accurately measure wind speeds for your specific site, use an anemometer, an instrument designed for testing wind speeds, that has an accuracy of at least 1% or +/- 0.2 m/s.
Set up your anemometer where you plan on siting your wind turbine (hopefully away from obstacles such as trees and buildings). Try to position it as high as possible to more accurately gauge what wind speed will be at the level of the turbine. Take readings regularly over the course of a few months or, if you have the time, an entire year to get as accurate data as possible.
Once you have collected all your wind speed data, add up all the numbers you have recorded and divide that figure by the number of readings you have taken to calculate the average annual wind speed for your location.
Taking the time and effort to conduct a full wind speed assessment will provide you with the most accurate gauge of wind speed for your location and will give you the peace of mind knowing how much wind you can expect to get from your site.
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