ABSTRACT

The two dimensional numerical method for analyzing a floating device with an Oscillating Water Column (OWC) type wave energy conversion device is introduced where the eigenfunction expansion method is described under the condition that the linear water wave theory is applicable. It derives the particular solution that satisfies the boundary condition on the water free surface in the air chamber and on the bottom of the floating device. A floating type device is moored on the water surface, which has an Oscillating Water Column at the front side. The floating device captures the wave energy using the heaving, pitching and surging motion of the device and the heaving motion of OWC. The method is proposed in order to calculate the device characteristics of an air chamber. It is confirmed that the solutions give good agreement with experimental results in this paper

INTRODUCTION

A wave-power-generating system of Oscillating Water Column (OWC) type is composed of a turbine-generator and an air chamber in which OWC converts wave energy into oscillating airflow (Raghunathan, 1995; Washio et al., 2000). A Wells type turbine is used for the air turbine because it is suitable for the operation in oscillating airflow. The Wells turbine will always rotate in the same direction irrespective of the direction of the oscillating airflow. Furthermore the Wells turbine has a simple configuration and structure. This is why it is very commonly used for conversion of wave energy. The Wells turbine has a special characteristics for the OWC which has a linear pressure drop over the blade against the flow rate under the constant rotational speed, that is, the load damping coefficient of OWC has linear characteristics (Suzuki, et al., 2000).

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