This paper presents a numerical study of the effects of blade roughness on wind turbine performance and annual energy production and how these effects may be partially mitigated through improved control. Three rotors are designed using the NACA4415, S801 and S810 airfoils, and blade element momentum theory is used to model wind turbine behaviour. The aerodynamic lift and drag data for the clean and roughened airfoils are taken from previous experimental work. These show that surface roughness leads to a decreased airfoil lift coefficient and an increased drag coefficient across an angle of attack range typical for large wind turbines, which will clearly lead to decreased turbine performance. Three separate control methods are considered for wind turbines with roughened blades operating at each of four candidate wind sites with different wind speed distributions. Results show that, compared to clean rotor blades, the roughened blades lead to a performance drop in the range of 2.9–8.6% for a torque based control strategy. A control‐based performance recovery strategy, in which the controller gain coefficient is re‐optimised, increased roughened rotor annual energy production by 0.1–1.0%.

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This paper presents a study investigating the effects of surface roughness on airfoil performance and its consequences for wind turbine energy yield. This study examined 51 sets of experimental data across 16 airfoils to identify trends in roughened airfoil performance. The trends are used to formulate a novel ‘roughness evolution parameter’ that can be applied to airfoils with no roughened data available to predict the impact of roughness on performance. Blade element momentum theory is used to model the performance of the DTU 10 MW reference wind turbine, with uniformly roughened blades emulated using the roughness evolution parameter. An annual energy production loss between 0.6–9.6% is found for the DTU 10 MW turbine when considering a plausible range of values for the roughness evolution parameter derived from the experimental data. A framework has been developed to evaluate how the roughness evolution parameter changes over time, informed by observed changes in wind farm performance from previous studies.