On the mitigation of detrimental effects via passive flow-control devices in small-scale horizontal-axis wind-turbines operating under turbulence and surface degradation effects

Abstract. Small-scale horizontal axis wind turbines (SHAWTs) installed in distributed grids are increasingly important for achieving net-zero emissions by minimizing visual and environmental impacts. However, the understanding of SHAWTs under combined turbulence and roughness conditions, operating at chord-based transitional Reynolds numbers ranging from 1 × 10⁵ to 5 × 10⁵, is still limited. This study examines the combined influence of environmental turbulence and surface degradation on a transitionally-operating NACA0021 airfoil equipped with passive flow-control devices (PDs) to mitigate detrimental effects. Results show that specific PD distributions can delay stall up to 5º and reduce performance loss by enhancing the aerodynamic efficiency up to 16 % under certain flow conditions.

Using experimental data, the study estimates the annual energy production (AEP) of a standard 7.8 kW-rated SHAWT using a blade-element method code. Simulations reveal that, when SHAWT blades are affected by turbulence and surface degradation along their entire span, certain PD distributions can enhance the AEP by up to 80 % compared to their bare counterparts. These findings highlight the potential of PDs in enhancing SHAWT's performance and the importance of pitch-regulated control in mitigating adverse effects.