AERODYNAMIC ROTOR BLADE DESIGN FOR SMALL WIND TURBINES WITH FOCUS ON TURBULENT INFLOW CONDITIONS

Abstract

Small wind turbines often have to operate in slow and highly turbulent wind. Whereas the aerodynamic design of rotor blades for small wind turbines is mostly based on tools and methods developed for large wind turbines, these aerodynamic requirements distinguish small wind turbines from larger models significantly. Nonetheless, steady blade element momentum (BEM) theory is employed to calculate the rotor aerodynamics, since this theory delivers reasonable results within a fast calculation time. Usually, steady state simulations which require much less computational effort than unsteady simulations tend to be preferred during the iterative design process of new rotor blades. This paper explores the worthiness of using computationally taxing unsteady flow simulations for determining the optimum rotor blade shape. A differential evolution algorithm in combination with an unsteady blade element momentum model is applied to derive an optimised blade shape for a small horizontalaxis wind turbine under turbulent inflow conditions. The results of this paper present, compared to steady optimisation, the effect of turbulent inflow on the optimum aerodynamic rotor blade shape and the rotor performance of a small wind turbine.