Fatigue study of an inverse-designed low induction rotor using open-source tools

The current trend in wind turbine design leans toward increasing rotor diameter for increased energy capture. This presents a notable fatigue concern as blade loads increase with blade length. One solution to potentially alleviate the additional blade loading and improve the fatigue behavior of large-diameter wind turbines, while also reducing overall cost of energy, is the low-induction rotor. The purpose of this work is to perform a holistic analysis to assess the attainable benefits of a notional low-induction rotor variant of the DTU 10MW Reference Wind Turbine using multi-disciplinary open-source design and analysis tools. The notional low-induction rotor blade is designed using an inverse-design routine that allows for the direct specification of desired blade properties. To assess viability of the new rotor design, annual energy production and levelized cost of energy are considered along with fatigue at the blade root and the associated drivetrain and tower response to changes in blade loading. It is estimated that the proposed early-concept low-induction rotor design improves annual energy production by 6.35% (or 3 GW-h), resulting in a 4% (0.25 ¢/kW-h) reduction in levelized cost of energy. The low-thrust nature of the low-induction rotor design reduces root flap bending moment fatigue by up to 21.5%, and it is proposed that changes in blade root edgewise fatigue for the longer, heavier blades of the low-induction rotor can be alleviated with mass redistribution.