Energy generation efficiency and strength coupled design and optimization of wind turbine rotor blades

Wind turbine rotor failures have been reported that resulted in substantial damage and cost for maintenance and recovery. This work developed a wind turbine rotor blade design and optimization method to address a coupled energy generation efficiency and blade structural strength design issue, as a generic procedure applicable to both turbine rotors and propellers, in air and water. The optimization procedure was developed for optimum radial blade sectional thickness distribution with a prescribed constant safety factor across the span. While maintaining the required structural strength and integrity of the rotor blades, this procedure is to achieve the following objectives: (1) reduce material use to minimum and (2) obtain the optimum power generation efficiency with the optimum structural strength. A propeller-turbine rotor code coupling aerodynamic and structural properties was developed. For a given blade geometry and chosen material, performance prediction of the instantaneous loading acting on all blade sections and the strength of a local blade section was performed and optimized. A time-domain, three-dimensional unsteady panel method was implemented, developed, and used to perform the optimization. A wind turbine 10 m in diameter from the National Renewable Energy Laboratory (NREL) (Golden, Colorado) was used as a base design example and for optimization based on an extreme wind speed of 100  km/h. The final result achieved a total savings of 18.72% in blade material.