Active load control applied to upscaled wind turbines: Design and cost impacts

Abstract

This study examines the combined effect of rotor upscaling and active load control (ALC), whereby ALC is used to offset the negative impacts of increased loads from an upscaled rotor that produces higher energy capture. Consequently, there is growing interest in innovative load control techniques to mitigate these excessive loads and their associated impacts on increased cost. In this study, ALC is implemented using controllable gurney flaps based on plasma actuators where we assess the impacts of upscaling and ALC on 1) loads of all major turbine components, 2) sizing of turbine components, 3) cost of energy including capital expenditures (CapEx), operating expenditures (OpEx), annual energy production (AEP), and ultimately the levelized cost of energy (LCOE). Additionally, ALC effects are examined for Region III-only operation and full-range, i.e., Region II and Region III. Upscaling is examined via two distinct scenarios: a power-uprated turbine design with a 6.3 % upscaled rotor and higher power rating (and higher structural loads), and a load-limited turbine design with the same increase in rotor size but maintaining the reference turbine power rating (to maintain or limit the load increase). Using a 3.4 MW reference wind turbine design, we maintain baseline performance limits with respect to the reference design for the tip deflection, mean stresses, and fatigue stresses in the upscaled design with ALC during the component resizing process. This resizing approach led to changes in CapEx, OpEx, AEP, and LCOE. Among the upscaled designs, the load-limited turbine with ALC achieved a slightly higher LCOE reduction of up to 4.9 % compared to 4.1 % for the power-uprated turbine, under full-range ALC operation. Overall, the load-limited upscaled design with ALC emerges as the marginally more favorable configuration, achieving greater LCOE reduction through a substantial AEP increase in Region II (due to upscaling), fatigue load reductions in critical components (via ALC), and relatively smaller capital cost increases compared to the power-uprated design, despite the latter yielding similar LCOE reductions. As a result, this work presents a comprehensive assessment of how ALC impacts component sizing and economics and compares upscaled designs (3.4B) with the 3.4A (retrofit) design, providing insights to designers and operators to most effectively use ALC in upscaled wind turbines.