Structural Optimization of 3 MW Wind Turbine Blades Using a Two-Step Procedure

Abstract

Modern large wind turbines, utilized to harness the kinetic energy of the wind, are rated at megawatts in output power. The design of large wind turbine blades must consider both their aerodynamic efficiency and structural robustness. This paper presents a two-step procedure for the optimum design of composite wind turbine blades. The results of the first step are the aerodynamically optimal cord lengths and twist angles of airfoils for the blade cross-sections along the blade spanwise direction. The second step yields optimal material distribution for the composite blade. A 3 MW wind turbine with blades having cross-sections of NREL S818, S825 and S826 airfoil types is demonstrated as the design example. Loaded by maximum forces and moments extracted from simulated time series, a parameterized finite element model of the aerodynamically optimized blade is created using the ANSYS software. The optimization results show that the initial blade model is an infeasible design due to a high level of the maximum stress, exceeding the upper limit of the stress constraint, but eventually the process converges to a feasible solution with the expense of increased total mass of the blade.