Special Issues on Design Optimization of Wind Turbine Structures

Abstract

Designers apply optimization techniques for improving performance and operational efficiency of wind turbines, especially in early stages of product development. It is the main aim of this chapter to present some fundamental issues concerning design optimization of the main wind turbine structures. Practical realistic optimization models using different strategies for enhancing blade aerodynamics, structural dynamics, buckling stability and aeroelastic performance are presented and discussed. Design variables represent blade and tower geometry as well as cross-sectional parameters. The mathematical formulation is based on dimensionless quantities; therefore the analysis can be valid for different wind turbine rotor and/or tower sizes. Such normalization has led to a naturally scaled optimization models, which is favorable for most optimization techniques. The various approaches that are commonly utilized in design optimization are also presented with a brief discussion of some computer packages classified by their specific applications. Case studies include blade optimization in flapping and pitching motion, yawing dynamic optimization of combined rotor/tower structure, and power output maximization as a measure of improving aerodynamic efficiency. Optimization of the supporting tower structure against buckling as well as the use of the concept of material grading for enhancing the aeroelastic stability of composite blades have been also addressed. Several design charts that are useful for direct determination of the optimal values of the design variables are introduced. This helps achieving, in a practical manner, the intended design objectives under the imposed design constraints. The proposed mathematical models have succeeded in reaching the required optimum solutions, within reasonable computational time, showing significant improvements in the overall wind turbine performance as compared with reference or known baseline designs.