Increasing turbine dimensions: impact on shear and power

As wind turbine average hub-height (H) and rotor diameter (D) grow, it is assumed that the benefit derived from larger swept areas and higher wind speeds at higher altitudes will outweigh any increase in fatigue loading due to higher shear and manufacturing/installation costs. The impact of increasing wind turbine H and D on power production and the occurrence of extreme positive and negative shear is examined using high-resolution simulations with the Weather Research and Forecasting (WRF) model over Iowa. Three wind turbine scenarios are considered; S#1: H=83m, D=100m; S#2: H=100 m, D=100 m and S#3: H=100 m, D=133 m. Increasing H from 83 m to 100 m while maintaining D=100 m increases power by 16% relative to scenario 1. Increasing D to 133 m from 100 m with H=100 m doubles the power output compared to S#1. Extreme shear across the rotor plane (shear exponent α > 0.2 or α < 0) is frequently observed, but only modestly impacted by the changes in wind turbine dimensions. Thus, the increase in power output from increasing H and D to these levels seems to incur little penalty in terms of increased occurrence of high positive or negative shear.