The blade design of a horizontal axis wind turbine (HAWT) prioritizes structural stability over aerodynamic performance, which results in power loss caused by stalling in the inboard regions. In this study, a vortex generator (VG) was employed for stall control. Because the generated vortex intensity varies with the VG geometry and size, design values based on the aerodynamic characteristics of airfoils in a wind turbine blade were considered. The VG design values for the HAWT were determined based on the computational fluid dynamics (CFD) analysis of the airfoil in the blade region with the maximum chord length. VG applicability was examined for all airfoils applied to the blade inboard region. Based on the lift and drag data obtained through the CFD analysis, the performance improvement of the wind turbine was analyzed through the blade element momentum theory. This analysis also incorporated the angle of attack of the airfoil, which differed for each local cross section in a wind turbine. The VG application increased the wind turbine power for each wind speed interval by an average of 2.5% and the annual energy production by up to 2.7%. The application of the proposed VG design to the inboard region can control the radial flow generated near the hub, improving the aerodynamic performance and decreasing the power loss.
Wind turbines installed in external environments are subject to a combination of various environmental and operational conditions during their lifetimes, resulting in varying mechanical loads on each of their components. These loads directly impact the turbine lifetime; therefore, research aimed at reducing the load on each component of the wind turbine is required. In this study, load analysis was performed by applying various load reduction control systems. The effect of the load reduction was verified for each controller through individual simulations. Finally, the design load cases (DLC1.1–DLC8.1) required to evaluate the ultimate and fatigue loads based on the IEC 61400-1 ed.3 international standard were defined, and the loads with respect to a 4 MW wind turbine with and without various load reduction systems were calculated. When applying all load reduction controllers, the turbine blades and the tower experienced ultimate load reductions of 1%–31% and 7%–21.7%, respectively, except the tower's side-to-side bending moment. This moment was observed in the idling condition, which was not affected by the control system; hence, no changes were observed in the load. Fatigue equivalent load reductions were also observed at the blade (3%–8.9%) and tower side-to-side load (4.8%–7.8%). Notably, however, the tower fore-aft fatigue load increased by 10% in most sections. This overall load reduction suggests that turbine components can be fabricated using less material, thereby increasing the wind turbine fatigue lifetime. This result is expected to reduce the levelized cost of energy.
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