Aero-structural rapid screening of new design concepts for offshore wind turbines

Abstract

The development of large-scale wind turbines is challenged by loads, mass, and cost growth, and more flexible blades that impact power and tower clearance. Further, the long-duration design iterations with standard-sequential-multidisciplinary processes challenge the development of new timely and robust designs. To overcome these limitations and answer open questions of large-scale wind turbines, we develop and demonstrate an aero-structural rapid screening (ASRS) design approach. ASRS uses optimization techniques, emulates a baseline controller, produces detailed blade, tower, and monopile models, and provides fast aerodynamic, structural, and economic results. Blade deflection is introduced as a design variable to achieve load-aligned designs as a function of wind speed for passive load alleviation. To illustrate the approach, a large set of 25 MW rotors for offshore and fixed-bottom wind turbines are studied for variations in blade pre-cone, load alignment via blade deflection, and upwind vs. downwind configurations. These designs vary in number of blades, blade length, axial induction factor, and airfoil family. We demonstrate that blade deflection can be designed to maximize energy capture and minimize turbine mass. ASRS is demonstrated to identify trends and trade-offs that are useful to down-select to options to be studied further using aero-servo-elastic simulations with high-fidelity control design.