Option 4. Long-Term Measurement
For turbines 10 kW or larger, you should consider undertaking long-term monitoring of hourly wind performance. This accurately confirms the wind performance and takes into account daily and seasonal effects of subtle variations in landscape and tree growth. This ensures you have sufficient wind present throughout the desired seasons to satisfy your electrical needs. If you decide on this method, do it soon enough in advance of wanting your turbine since you will need at least one year's worth of data.
A data logger can be used to record instantaneous observations of wind speed measured with an anemometer, or to store a long-term record for later analysis. Software is also available from some equipment suppliers to automatically analyze your data. Some systems can also be rented.
If you hire a specialist to do the wind study, he or she will provide the necessary equipment, but you should inquire about the type of equipment the specialist is using, and the amount and quality of data to be gathered.
See Links for more resources on wind measurement.
An anemometer (seen above, courtesy of the NRCan Small Wind Buyer’s Guide) is an instrument that turns faster as the wind increases, thereby allowing you to measure the windspeed by visual or automated means. An anemometer can cost between $100 for a simple unit to $5,000 for an automated standalone unit with data storage. The measurement equipment must be set high enough to avoid turbulence created by trees, buildings, and other obstructions. The most useful readings are those taken at hub-height, the elevation at the top of the tower where the wind turbine would be installed.