SummaryA primary conversion efficiency of a floating OWC-type wave energy converter "Backward Bent Duct Buoy (BBDB)" in regular waves is investigated in 2D and 3D wave tank tests. Firstly, the amplitude and phase difference between the internal wave height and motions are investigated. In a 3D tank test, surge, heave and pitch become in-phase at efficiency become maximum. The phase of internal wave height is close to motion. Secondary, the efficiency of duct-extended buoy is investigated in 2D test. Efficiency is reduced because the pitch becomes small by duct extension. Thirdly, the effect of a moment of inertia is investigated. In case of total mass and draft is constant, frequency band of high-efficiency increases as the moment of inertia become large. Fourthly, the effect of the shape of the air chamber is also investigated.
Abstract:For the practical application of a fixed oscillating water column (OWC)-type wave energy converter, it is necessary to develop a design method which can consider the characteristics of incident wave motion, the motion of the internal free surface affected in the structure such as a partly submerged wall, the fluctuation of air pressure in an air chamber, and the rotation of the air turbine. On the other hand, the impulse turbine as the secondary conversion device in the OWC unit is expected to achieve high efficiency. In this paper, firstly, the steady air flow tests for a single-impulse turbine were conducted to grasp the characteristics of the turbine without the effect of water waves. Secondly, the 2-dimensional wave tank tests in regular waves for the performance evaluation of the fixed OWC-type wave energy converter with the same impulse turbine were conducted to obtain the data needed to make this design method. As the results, the effects of the air chamber length and the guide vane's setting angle on the primary and secondary conversion efficiencies are clarified experimentally.
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