In an Oscillating Water Column (OWC) based wave energy plant, an air turbine is operated through bi-directional airflow generated by the reciprocating motion of water column in the air chamber. A sail wing turbine can be used as an air turbine for wave energy conversion because it has a special structure in which the shape of the sail changes in reciprocating airflow and always can rotate in the same direction. This turbine is generally used for wind power generation and recently adopted as a turbine for wave energy conversion. This turbine has simple construction and its manufacturing cost seems to be lower. However, its efficiency is worse than other conventional turbines at present. In order to improve the turbine performance by means of guide vane, a wind tunnel test under steady flow and a CFD analysis were conducted to investigate the turbine characteristics in the study.

A counter-rotating tidal stream power unit is composed of tandem propellers driving double rotational armatures, while the rotating torques are counter-balanced in the power unit. The power unit can be moored with one cable and keep the posture stable without rolling motion in the tidal stream, in which the cable is hooked at the balancing point of the moment among the buoyancy, gravity and drag. The posture, however, may lose balance by a dynamic disturbance. In order to keep the posture stable in every circumstance, the winglets were installed on the rear blades. In this research, effectiveness of winglets in case mooring with a wire near the water surface was verified by the circulation type water channel test. Besides, the blade performance was analyzed by the CFD. As the result, it is noticed that the high blade load can be achieved at near the blade tip by setting the winglets.