Validation of kinematic wind turbine wake models in complex terrain using actual windfarm production data

Abstract

Measurements from a wind farm in northern Norway have been used in an attempt to validate three kinematic wake models, which are often preferred due to their efficiency in terms of calculation time. Assisted by the commercial CFD-based WindSim software, the accuracy of the Jensen-, Larsen- and Ishihara model are tested in eight single-wake cases with regard to several key aspects. Due to the complex terrain at the site, a range of issues complicated the validation procedure. The Larsen model correlated well with the measured data regarding the normalized power deficit, while both the Jensen- and Ishihara model clearly overestimated the power deficit. At the wake centerline, the Larsen model was by far the most accurate, with a mean absolute error of 7%. The Jensen- and Ishihara model had a mean absolute error of 21% and 34% respectively. Both the Jensen- and Ishihara model agreed well with the observed wake width. The Larsen model widely overestimated the wake width in all cases, but with an almost constant offset. For the energy loss in the wake, the Larsen model performed best for the three investigated wake cases with a mean absolute error of 29%, although all the three wake models showed a varying performance with a tendency to underestimate the energy loss.