by Chris Floate

Created on: October 27, 2010   Last Updated: October 28, 2010

Wind turbines - why you can't use average wind speeds

I’ll try to keep this as simple as possible, after all, what we are trying to do is decide if a wind turbine will be suitable for a particular site and to do that we need our wind speed data.

It is important to understand why we can't just use the government's average wind speed for the postcode or grid reference of the site. The average wind speed for a location I am currently monitoring is 6.5m/s (about 14mph) and that's a pretty good average wind speed wind. To demonstrate the problem we need an imaginary wind turbine. If we select the Evance 9000 wind turbine as an example we can show just how inaccurate using a broad average for the year can be.

If we take a week’s wind data as shown below, we can see that we had a quiet start to the week, then some strong winds than calm again at the end of the week.

 Wind                 Power
 Speed m/s      generated w
 0                           0
 1.5                        0
 2                           0
 12                         5137 
 14                         5015 
 15                         5112 
 1                           0 

Ave 6.5m/s          2180 watts

With these figures the week's average works out to 6.5m/s, the same as that given for the site, but if we equate Evance’s power data (from their specification sheet) to the daily averages attained, we would

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