Abstract
AbstractThis 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%.
Highlights
Wind turbine performance can change as the aerodynamic quality of the blade surface degrades over time
The impact of roughness on a turbine's annual energy production (AEP) is a combination of the reduction in turbine performance caused by the roughness source(s), predominantly encountered below the turbine's rated power and the wind speed distribution, that is, how likely the turbine is to be operating below the rated power
Three turbine control strategies have been investigated with an in-house analytic blade element momentum (BEM) model; two widely adopted in the literature and a novel third control strategy that seeks to mitigate some of the effects of roughness on turbine performance and AEP
Summary
Wind turbine performance can change as the aerodynamic quality of the blade surface degrades over time. Multiple experimental tests have been performed to measure the impact of icing on the aerodynamic performance of an airfoil.[5,6,7] Krøgenes and Brandrud[6] and Hann et al[7] both investigate the impacts on the NREL S826 airfoil under different icing conditions Their results were synthesised by Vinnes and Hearst[8] and showed a 10% decrease in lift and 80% increase in drag. Blasco et al[5] analysed the effect of icing on an airfoil using wind tunnel experimental testing They used blade element momentum (BEM) software XTurb-PSU12 to conclude that the changed aerodynamic performance of the airfoil implied a 16–22% reduction in power for a wind turbine in freezing fog conditions and 26% for a freezing drizzle condition. Three turbine control strategies have been investigated with an in-house analytic BEM model; two widely adopted in the literature and a novel third control strategy that seeks to mitigate some of the effects of roughness on turbine performance and AEP
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