Performance characteristics and parametric analysis of a novel multi-purpose platform combining a moonpool-type floating breakwater and an array of wave energy converters

Abstract

Integration of Wave Energy Converters (WECs) with floating breakwater system provides a multi-function solution to wave energy extraction and offshore infrastructural protection. The contribution of this work is to guide the optimal size and configuration of a multi-purpose platform including a moonpool-type floating breakwater and an array of heaving oscillating-buoy (OB) WECs. The investigation is performed using a developed time-domain numerical wave tank (NWT) based on the three-dimensional (3D) potential flow theory with fully nonlinear boundary conditions on transient wetted body surfaces and free surfaces. The comparison of the hydrodynamic performance among the multi-purpose platform, the isolated array WECs, and the isolated floating breakwater are examined. The internal fluid motion in the moonpools has a positive effect on the wave energy absorption of WECs, which in turn enhances the wave attenuation capacity of the floating breakwater. WECs with larger diameter have a larger water-plane area, which leads to more extracted wave energy. The wave nonlinearity reduces the optimal PTO damping value and has an adverse effect on the wave energy extraction. However, when wave nonlinearity becomes prominent, the wave attenuation capacity is improved with increasing PTO damping. For an unequal layout of moonpools, the thinner moonpools are the major contributor to wave energy extraction, especially in the short wave region. As a result of mass exchange of fluid from the moonpool to the outer domain, the multi-purpose platform indicates favorable performance of wave energy absorption. The novel floating system makes the utilization of wave energy over a wider frequency range.