Innovative aerodynamic rotor concept for demand-oriented power feed-in of offshore wind turbines

Abstract

We introduce an aerodynamic rotor concept for a 15 MW offshore wind turbine which is tailored for an increased power feed-in at low wind speeds. The main objective of the conceptual design is to limit the stationary loads (blade flapwise root bending moment (RBM) and thrust) to the maximum value of the IEA 15 MW offshore reference turbine, while greatly increasing the swept rotor aera. The outer part of the blade (e.g. outer 30% of the rotor) is designed for a higher design tip speed ratio (TSR) and a lower axial induction than the inner part. By operating at the high TSR in light winds, the slender outer part fully contributes to the increased power capture. In stronger winds the TSR is reduced and the torque generation is shifted to the inner section of the rotor. Moreover, the blade is designed in a way that makes the limitation of the flapwise RBM through peak shaving aerodynamically more efficient. With static blade element momentum simulations the characteristics of the rotor are investigated and the economic revenue of the turbine is estimated, considering a wind speed dependent feed-in price. Our results show that the revenue can be increased by 30% compared to the reference turbine with an increase of rotor diameter by 36%.