Abstract
Oscillating water column (OWC) devices are the most successful devices for extracting energy from ocean waves. In oscillating water column devices, the air turbine section is of either horizontal or vertical orientation. An experimental study is carried out to compare the airflow characteristics and turbine rpm in horizontal and vertical turbine sections of an oscillating water column device. Two OWC models, one with a horizontal duct connecting the turbine to the atmosphere and the other with a vertical duct, were tested at mean water depths of 230 mm, 260 mm and 290 mm and at frequencies of 0.6 Hz, 0.7 Hz, 0.8 Hz, 0.9 Hz, 1.0 Hz and 1.1 Hz. Mean total pressure profiles were plotted just upstream and downstream of the turbine section for different cases, while instantaneous static and dynamic pressure measurements were performed to study their variations with time at these locations. A Savonius type rotor was used as a turbine and its rpm was measured and at the above depths and frequencies to compare the performance of the two OWC models. The OWC model with the horizontal turbine section showed better performance characteristics compared to the OWC with the vertical turbine section. RPM values were 20–30% greater in the horizontal turbine orientation compared to the vertical one. The successful use of a Savonius type rotor as a good and cost-effective option for energy conversion is emphasized in this work.