To What Extent Is Aeroelasticity Impacting Multi-Megawatt Wind Turbine Upscaling? A Critical Assessment

Aeroelasticity is recognized as the key enabler that allowed for the massive upscaling of wind turbines in the last decade, leading to long, slender, and flexible blades that equip rotors with lower specific power and unprecedented energy conversion capabilities. In this study, a selection of case studies with increasing size, specifically the NREL 5 MW, the DTU 10 MW, and the IEA 15 MW Reference Wind Turbines (RWTs) is considered to explore to what extent aeroelastic effects impact the functioning of these rotors. The rotors are not only different in size, with the 15 MW having blades nearly double the length of its 5 MW predecessor, but also in technological level as they belong to different phases of wind turbine development. To evaluate how these machines interact with complex inflow conditions, equivalent boundary conditions have been considered for all simulations, including a realistic atmospheric boundary layer, atmospheric turbulence, and wind shear. To carry out the comparative study, a new aero-servo-elastic module called CALMA is introduced herein, by coupling the engineering software OpenFAST with the CFD software CONVERGE, which solves the wind field and provides inflow conditions for the calculation of loads. Results show how not only aeroelasticity increasingly affects the power performance of the new-generation rotors, but is also a key driver of structural design, for example allowing for an alleviation of 1P load variations due to a sheared and turbulent inflow, thus proving that the inclusion of aeroelasticity in the design process is a key enabler to current and future upscaling trends.