Hydrodynamic performance of wave energy converter integrated with pile restrained floating structure near a partially reflecting seawall

Abstract

The integration of a Wave Energy Converter (WEC) with a Pile-Restrained Rectangular Floating Breakwater (PRFB) in the presence of a partially reflecting vertical seawall is analysed to enhance the hydrodynamic performance and WEC efficiency of the integrated breakwater-WEC device based on small amplitude wave theory using the Boundary Element Method (BEM). The rectangular floating breakwater is designed to have heave motion with a pile-restrained floating structure placed in a position to attenuate the incoming wave in the transmitted region and the linear power take-off (PTO) damping is employed to calculate the absorbed power. The study is performed to understand the effectiveness of wave energy conversion and its hydrodynamic performance due to changes in the seawall's porosity, relative structural width, relative structural draft, wave energy conversion power take-off damping coefficients, and the relative gap of the WEC integrated with PRFB from the seawall. The study demonstrated that in the presence of a fully reflecting seawall, the wave energy extraction is enhanced for the integrated WEC system without compromising the defined threshold wave reflection coefficient but at the expense of a constrained range of wavenumbers that correspond near the system's fundamental natural frequency. Moreover, the capture width ratio is noted to be higher for relatively smaller structural drafts, while the wave reflection coefficient shows precisely the reverse trend. However, under such circumstances, the integrated WEC system operates as a motion-trapping structure, especially when the reflection coefficient of the seawall, CR≥0.75. Thus, the present study will assist the designer in determining the appropriate degrees of efficiency of the WEC device without sacrificing hydrodynamic performance by fine-tuning the hybrid floating breakwater system's geometrical parameters.