Wave Power Absorber Utilizing Anti-Pitching Tank

Abstract

This paper presents the basic design procedure of the wave power absorber utilizing the anti-pitching tank (A.P.T.). The A.P.T. is carried on the ship and converts the wave energy to the tank water oscillation. It is further imagined to absorb the energy through the air turbine and the generator. The optimum conditions of maximizing the absorbed wave power are following: (1) the resonant periods of tank and ship should be equal to the design period of the incident waves, (2) the damping added to the tank should be adjusted so that the absorbed power is equal to the radiating power due to the pitching of ship. The design procedure is assured through the model tests. It is however found that the A.P.T. should contain the significant mass of water relative to total displacement of ship and its horizontal part should be long enough, and that the ship should be designed to have a long pitching-period on securing of stability. The flat tank and the shallow draft ship with elliptical plan form are designed and the wave power absorbing characteristics are analysed. It shows a good performance and is expected to be feasible. Additionally, in this type of wave power absorber the mooring force is relatively small and the working fluid is closed in the tank so that the maintenance is rather free than the conventional O.W.C. devices.