Counter-rotating impulse turbine for wave energy conversion — Performance improvement by means of middle vane

In a wave energy converter with oscillating water column (OWC), an OWC due to the sea wave motion is used to drive an air column in the air chamber. An air turbine for this bidirectional airflow is used to convert the pneumatic energy into the mechanical energy. In this study, in order to achieve further improvement of the performance of a counter-rotating impulse turbine, the effect of turbine geometry on the performance was investigated by using the computation fluid dynamic (CFD) analyses. As a result, it was found that the efficiency of the turbine greatly increased by installing the middle vanes.