Performance of Ducted Savonius Turbines with different blade configurations and at different Turbulence intensities for Tidal Current Energy Extraction

Abstract: Marine current energy is a reliable and clean energy source. A ducted Savonius turbine was designed for a location in Fiji for marine current energy extraction, and the passage is called a gun-barrel passage. The average marine current speed at this location is 0.85m/s, and the maximum marine current velocity exceeds 2.5m/s. The model of the ducted Savonius turbine, scaled down to 1:12, was fabricated and tested in a water stream at the free stream velocity of 0.6m/s. Commercial Computational Fluid Dynamics (CFD) code ANSYS-CFX was then validated with experimental results. A full-scale numerical model was constructed to study the flow characteristics and for performance analysis. Finally, the model was modified to improve its performance. The performance analysis was done at free stream velocities of 1m/s, 2m/s, 3m/s, and 4m/s for 3 blades, 5 blades, and 7 blade rotors. A 3 blade rotor performed better when compared to 5 and 7 blade rotors, achieving a maximum theoretical efficiency of approximately 50% at 2m/s. For the case of 3 blade turbine, there is a drop in efficiency by 8%, as the turbulence intensity increases from 1% to 60% and at 2m/s. The efficiency drops by 5% and 2.5% for the case of 5 blade and 7 blade, respectively, as the turbulence intensity increases from 1% to 60% at 2m/s. Keywords: Fluid Mechanics, Renewable Energy, Tidal Current Energy, Ducted Savonius Turbine