The spacing of wind turbines in large arrays

The effect of spacing on the power output of wind turbines in large arrays has been determined theoretically. Following Templin, the effect is assessed by determining the increase in roughness of the earth's boundary layer due to the drag of the turbines. The thickness of the boundary layer is assumed to change in proportion to the square root of the skin friction, which is appropriate for a turbulent Ekman layer, and differs from the assumptions made by Templin. The loss of power for both flat-open country and rough-wooded country is determined as a function of the area density of the turbines, and it is found that quite large spacings are required to avoid a significant loss of power.