Articles | Volume 2, issue 2
Wind Energ. Sci., 2, 403–413, 2017

Special issue: The Science of Making Torque from Wind (TORQUE) 2016

Wind Energ. Sci., 2, 403–413, 2017

Research article 27 Jul 2017

Research article | 27 Jul 2017

Design of advanced airfoil for stall-regulated wind turbines

Francesco Grasso1, Domenico Coiro2, Nadia Bizzarrini2, and Giuseppe Calise2 Francesco Grasso et al.
  • 1Aerodynamix, Naples, 80128, Italy
  • 2Dip. Ingegneria Industriale, Università di Napoli FedericoII, Naples, 80123, Italy

Abstract. Nowadays, all the modern megawatt-class wind turbines make use of pitch control to optimise the rotor performance and control the turbine. However, for kilowatt-range machines, stall-regulated solutions are still attractive and largely used for their simplicity and robustness. In the design phase, the aerodynamics plays a crucial role, especially concerning the selection/design of the necessary airfoils. This is because the airfoil performance is supposed to guarantee high wind turbine performance but also the necessary machine control capabilities. In the present work, the design of a new airfoil dedicated to stall machines is discussed. The design strategy makes use of a numerical optimisation scheme, where a gradient-based algorithm is coupled with the RFOIL code and an original Bezier-curves-based parameterisation to describe the airfoil shape. The performances of the new airfoil are compared in free- and fixed-transition conditions. In addition, the performance of the rotor is analysed, comparing the impact of the new geometry with alternative candidates. The results show that the new airfoil offers better performance and control than existing candidates do.

Short summary
The majority of the wind turbine market is focused on large pitch-regulated machines, but small stall-regulated are still attractive because of their simplicity and robustness. This work focuses on aerodynamic section design for these machines and its impact on overall performance. The big challenge faced was that, beside the need to maximise the energy produced, the control of the machine depends on the section design. The results, however, showed a large performance gain and machine control.