Multi-objective optimization and experimental testing of a laminated vertical-axis wind turbine blade

Abstract

Vertical-axis wind turbines, despite being somewhat uncommon and less efficient renewable energy converters, still offer many advantages to small consumers and possibilities for further improvement. Their rotor is usually made up of fiber-glass composite blades that can be optimized both aerodynamically and/or structurally. Although the aerodynamics of vertical-axis wind turbine rotors is unsteady, complex and challenging to simulate, it is possible to make a sufficiently accurate estimation of variable aerodynamic loads acting on the blade and use them for its structural dimensioning. This research combines a multi-objective constrained optimization procedure by particle swarm and finite element method with experimental analyses with the purpose of defining the best blade, i.e. the blade of minimal mass, least tip deflection under the loading case corresponding to the aerodynamically most demanding operational regime, greatest difference between its natural frequencies and rated rotor angular frequency, lowest manufacturing cost and complexity, etc. Imposed constraints also include acceptable failure criteria along the blade. Design variables refer to ply lay-up scheme, i.e. lamina thicknesses and orientations. Final solution, chosen from the obtained Pareto set, was manufactured and experimentally validated. The consistency of strains, measured in several different cases of bending, and corresponding numerical values was mostly below 8%. The study demonstrates the applicability of the employed multi-objective optimization methodology in wind turbine blade design. It also proposes an affordable and structurally reliable composite lay-up scheme specifically designed for small-scale vertical-axis wind turbines.