The top-down model of wind farm boundary layers and its applications

A simple model for the interactions of large wind farms with the turbulent atmospheric boundary layer, augmented for wake effects, is used to examine several important aspects of power degradation in large wind farms. It is shown that when combined with a model for internal boundary layer growth following the start of a wind farm, the model can explain measured power degradation trends. The model is then used to re-examine the advantages of off-shore wind farms. It is shown that the smaller roughness length over ocean that leads to faster hub-height winds compared with land-based wind farms is largely overshadowed by the wind turbines themselves.