Design Optimization of 10MW Downwind Turbines with Flexible Blades and Comparison with Upwind Turbines

Abstract

Downwind turbines can adopt light and flexible blades because of limited risk of tower-strike. We investigate superiority of a downwind configuration in large-scale wind turbines with high extreme wind speed through comparison of optimized 10 MW downwind and upwind turbines. Blades and towers of these turbines are optimized to minimize their levelized cost of energy (LCoE) with steady state aero-structural analyses considering tower shadow and potential flow effects on power production and fatigue damage. Comparison shows that the optimized downwind turbines have an advantage in LCoE due to their lighter and more flexible blades than the upwind turbines with conventional prebend of 6 [m]. This advantage is derived from smaller thrust force, lighter rotor-nacelle-assembly, and a small distance between a tower axis and center of gravity of the rotor-nacelle-assembly. The upwind turbine requires 11 [m] prebend to obtain the comparable LCoE to the downwind turbine.