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Investigations of upscaling effects for aerodynamic design of large wind turbine rotors by using BEM theory and optimization

Kesikbaş, Ozan.
In recent years, wind power has become one of the most preferred and accepted renewable energy sources. However, there are still design challenges of new wind turbines especially upscaling problems as the size of rotor blades gets larger and larger. The main objective of this research is to understand scaling effects on wind turbine design by investigating and developing new design and scaling methodologies. For the design studies, the 5 MW NREL wind turbine is used as the baseline rotor. For the upscaling studies, this selected 5 MW baseline wind turbine is scaled up to 10, 15 and 20 MW wind turbines by using the classical upscaling method which is a linear scaling rule. For the optimization studies based on the blade element momentum theory and multipurpose genetic algorithm, the 5 MW NREL wind turbine blade which is taken as the reference blade is first optimized and analyzed. Then, the aerodynamic shape and blade mass of the upscaled 10 MW, 15 MW and 20 MW wind turbines are optimized. The optimization studies are conducted to maximize power generation and minimize blade mass. The aerodynamic and structural parameters of the rotor blades such as chord length, twist angle, blade mass and blade stiffness are compared. Then, the aerodynamic and structural performance analyses are done by using the FAST software and the results are compared for the reference blade, upscaled blades, and optimized blades. Finally, based on the results for the optimized wind turbines, new scaling trends are formulated as a function of rotor diameter to understand the re-sizing effects on wind turbines.