Handbook on obstacle wake effects related to wind turbine siting

On the basis of an extensive literature study a method has been developed to determine the velocity reduction in the far wake of obstacles in the atmospheric boundary layer. Compared to the near wake this far wake is the most important with regard to wind turbine siting, as close vicinity to obstacles will mostly be avoided because of the expected hazardous turbulence effects of the approach wind on the wind loading of the wind turbine and the reduction of its power output. An attempt is made to a systematic approach, in which all flow and obstacle effects are incorporated, although as yet not every parameter has been equally well investigated. The method classes any obstacle shape in one of three categories: houses, trees or dikes. Main graphs give the velocity reduction for these categories, for standard conditions of the approach flow and obstacle shape. By means of correction graphs the effect of non standard conditions can be accounted for.