Performance Characteristics of Vertical-Axis Off-Shore Savonius Wind and Savonius Hydrokinetic Turbines

Abstract

The rise in energy demand, climate change and depletion of fossil fuel, encourages the researchers to find a solution to the scarcity of clean energy. Therefore, the extraction of energy from renewable energy sources has become a topic of interest in the past few decades across the globe. Thus, harvesting the offshore wind and hydro energy and converting it to electrical power using various electromechanical devices has been a challenge. In this context, the vertical-axis Savonius wind and Savonius hydrokinetic turbines appear to be promising concept for energy conversion because of their good self-starting capability and simplicity in design. The present study attempts to characterize the performances of a Savonius wind turbine (SWT) and a Savonius hydrokinetic turbine (SHT) under identical input flow conditions. In order to characterize their performances, the SWT is tested in a low-speed wind tunnel with closed test section whereas the SHT is tested in an open channel flume. In each case, the torque and power coefficients are estimated at different mechanical loading conditions. It is observed that the SWT and SHT demonstrate peak power coefficients of 0.25 and 0.28 respectively for the same input power. However, the SWT is found to operate over a slightly wider range of tip-speed ratios than the SHT before the onset of stall. Finally, the computational study using ANSYS 14.5 has been carried out to evaluate the flow physics of the turbine at various azimuthal positions.