How to Analyze Wind Data

Many do-it-yourselfers rely on monthly and annual wind speed averages to evaluate a site’s potential. The data analysis required in these cases is fairly straightforward and is usually explained in wind instrument manuals. The interpretation of more detailed or lengthy data, such as daily or hourly readings over a year, might require the expertise of a specialist. If you choose to do all of the data analysis yourself, a local meteorologist or wind turbine dealer may be willing to check your results at no charge.

For example, if you measure monthly average wind speeds at your site for only six months, you can estimate how much wind you are likely to get over an average year by correlating your data with that from a nearby IEC wind monitoring station. To do this, take the average speeds at both sites during the monitoring period. Divide your average by the average speed at the IEC station and you will get a correlation factor. To find your site’s estimated annual average wind speed, multiply the IEC station’s annual average by your own correlation factor.

In this example, your site’s estimated annual average wind speed is 11.1 mph x 0.93 = 10.3 mph

Ideally, the correlation should be done for each of eight sectors of wind direction. What makes each potential site unique is the turbulence-creating effects of the terrain and nearby trees and buildings. These effects will be more noticeable in certain wind directions, so you need to create a monthly summary of wind speeds by direction for your intended site and the IEC station and then create a correlation for each direction. These correlations can then be applied to annual wind data and weighted according to the prevalence of winds by direction. Contact the IEC for average monthly wind speeds at a site near your intended wind turbine location.