Evaluating a vertical axis wind turbine for improved energy capture in low-wave OWC

Abstract

This paper investigates the energy harvesting efficiency of fish-ridge and Savonius turbines within an Oscillating Water Column (OWC) system. The main objective is to design and evaluate the performance of both turbines using a comparative analysis approach. After successfully identifying and comparing the performance characteristics of the fish-ridge and Savonius turbines, controlled experiments were conducted using a purpose-built OWC test apparatus. The simulations and experimental tests reveal that within the OWC system, the fish-ridge turbine achieves a Power Coefficient (CP) of 30%, whereas the Savonius turbine reaches only 24%. Additionally, the fish-ridge turbine demonstrates a torque extraction efficiency of 75.2% at a Tip Speed Ratio (TSR) of 0.4. It also initiates rotation at a lower wind speed of 0.8 m/s, achieving a steady speed of 450 rpm at 2 m/s, while the Savonius turbine requires a higher wind speed of 1.5 m/s to start and maintains 380 rpm at 3.25 m/s. These results indicate that within the OWC system employing a Vertical Axis Wind Turbine (VAWT), the fish-ridge turbine exhibits greater sensitivity to lower wind speeds compared to the Savonius turbine, making it a more efficient option for low-wave energy conditions.