Energy Generation Efficiency due to Wave Overtopping on Floating-Overflow-Type Wave Energy Converter

Abstract

The current heightened interest in renewable energy motivated this investigation into the efficiency of wave power generation, which can produce electricity from the infinite energy source of ocean waves. The subject chosen was a floating-overflow-type wave energy converter (FOWEC), which is a comparatively simple type of power generation equipment among the various types of wave power equipment. Because FOWEC is a floating body, it functions not only for power generation, but also as a floating breakwater. In this study's hydraulic model experiments, FOWEC time waveforms were measured, and the reflection and transmission coefficients were computed. In addition, the outflow velocity from the FOWEC overtopping water tank was measured and compared with the theoretical value. The results confirmed that the FOWEC exhibited some degree of wave control in its role as a floating breakwater. The freeboard for the overtopping waves on the lowest FOWEC had an average wave reflection coefficient of 0.43 and an average wave transmission coefficient of 0.21. As wave overtopping increased (as the freeboard decreased and the incident wave height increased), the effective velocity ratio of the outflow from the overtopping tank increased. However, as the freeboard decreased, the effective head decreased, and therefore the energy that could be received was smaller than when the freeboard was higher. In order to maximize the generation efficiency, conditions that allow for overtopping should be implemented with a FOWEC that can maintain an optimal freeboard for appropriate wave overtopping and effective head.