Analytical and experimental study on tandem WEC-type floating breakwaters

Abstract

Tandem wave energy converter (WEC)-type floating breakwaters, which is expected to overcome the shortcomings of the single-pontoon system (i.e., the narrow effective frequency bandwidth for the effective transmission coefficient KT < 0.5 and the qualified capture width ratio CWR η > 20%), is proposed. The tandem-pontoon system consists of a pair of single-pontoon WEC-type floating breakwaters (details see Ref. [1]). An analytical method based on linear potential flow theory is adopted to predict the hydrodynamic performance of the singlepontoon and tandem WEC-type floating breakwaters, respectively. Analytical solution showed that the effective frequency bandwidth for the tandem-pontoon system is obviously broader than that for the single-pontoon case. Note that, economically, the volume of the tandem-pontoon system equals to that of the original single-pontoon system. Furthermore, to confirm the phenomenon of boarder effective frequency bandwidth found by analytical method, an experimental study is conducted to investigate the hydrodynamic performance of the WEC-type floating breakwater. The power take-off (PTO) system consisting of the magnetic powder brake, the current controller and the torque-power sensor is used to measure the produced power and the damping force. Experimental results also reveal that the tandem-pontoon system performs more effective than the single-pontoon system in terms of the effective frequency bandwidth.