Very accurate measurements of the wind speed are essential to the wind energy community. This is a fact for measurements of wind resources, which determines the overall driving economics of wind energy. But it is even more true for measurements of the power performance of wind turbines, on which manufacturers sell their wind turbines and for which contractual agreements determine whether the individual wind turbines are able to perform satisfactory or not. In the latter case, the wind speed measurement is the most important single contribution to the uncertainty of the power performance measurement. The wind speed sensors are therefore, by no discussion, the most important instruments to the wind energy community.
So far, cup-anemometers have been dominating in wind energy applications. They are being used predominantly in wind energy assessments, and they are at present the only instruments being accepted in power performance measurements in international standards. The reason why the cup-anemometer is so successful is the simple construction, the low price, and yet very good characteristics.
A variety of cup-anemometers are available on the market. Sizes, cup shapes, body shapes and dimensions vary significantly on different designs. A number of investigations have been made to evaluate cup-anemometers for wind energy applications. The problem is, that the selection criteria for the specific applications need to be based on adequately detailed investigations of each specific cup-anemometer design. Despite the efforts so far, it is still a difficult task to set up objective criteria to classify cup-anemometers for given purposes.