Determination of Optimal Geometry for an Empty Concentrator Augmented Wind Turbine

Abstract

Aims: To determine the optimal concentrator geometrical parameters of an empty concentrator augmented wind turbine (CAWT), which are used to design and install CAWTs. Place and Duration of Study: Physics Department, University of Fort Hare, South Africa between March 2023, and October 2023. Methodology: The study used the concentrator length (L) to concentrator outlet diameter ratio (Lr) and the difference between inlet and outlet radii to concentrator outlet diameter ratio (Rr) to investigate the effect of concentrator geometry on wind velocity augmentation and air dynamics to determine the optimum concentrator geometrical parameters using computational fluid dynamics modelling. The modelled concentrators’ geometry was created in SolidWorks, prepared for meshing in SpaceClaim, meshed, and analysed in Fluent to solve the Reynolds-averaged Navier-Stokes equations, and validated by primary experimental results. To make the concentrators, six equally spaced Lr were used in the range 0.1 \(\le\) Lr \(\le\) 0.6  and thirteen equally spaced Rr in the range 0.025 \(\le\) Rr  \(\le\) 0.325 . The concentrators’ performance was investigated in terms of velocity augmentation ratio (Vr) and concentrator efficiency (\(\eta\)c). Results: It was observed that the variation in Vr was influenced by the change in both Lr and Rr. The Vr and \(\eta\)c   increased with an increase in Lr to a maximum at optimum Lr  and decreased thereafter. The optimum Vr was obtained at Lr = 0.4 and Rr  = 0.1 with a maximum velocity at the concentrator outlet. It was also shown that the energy losses due to friction negatively impact velocity augmentation more than energy losses due to a large concentrator tilt angle at high Lr . Conclusion: When constructing a CAWT, the turbine rotor should be placed at any distance between the concentrator outlet and 0.5L  behind the concentrator, and the blade tips of the turbine in a CAWT system should be at least 10% smaller than the concentrator outlet radius, for the whole rotor to receive wind with augmented velocity.