On the potential value of interval deficient wind data

The stringent requirements of standards for wind measurements such as IEC 61400-12-1:2005(E) suggest that wind data produced by systems and procedures that do not comply with these standards are deficient and therefore not of sufficient quality for use in wind energy applications. In particular, the standard implies that data are deficient if acquired either intermittently, or continuously - but at averaging intervals exceeding the specified requirements. In order to demonstrate that certain deficient data may in fact be useful in wind energy applications, sets of interval deficient wind data of varying lengths of intermittency - and averaging interval are synthesized from ideal quality data sets produced by systems that closely comply with IEC 61400-12-1:2005(E). Weibull parameters are identified for the data sets and compared. It is inter alia shown that parameters identified from annual sets of wind data acquired at four widely dispersed compliant measurement stations in Southern Africa are remarkably insensitive to the length of intermittency interval and that the parameters can be identified with a relative error of 1% or better for intermittency intervals of up to 1 h or longer. This finding suggests that data sets acquired via historic wind measurement devices may indeed be valuable.