Hydrodynamic performance of a dual-floater hybrid system combining a floating breakwater and an oscillating-buoy type wave energy converter

Abstract

The high power generation cost impedes commercial-scale wave power operations. The main objective of this work was to provide a cost-sharing solution through combing the wave extraction and costal protection performance. A two-dimensional numerical wave tank was developed using Star-CCM+ Computational Fluid Dynamics software to investigate the hydrodynamic performance of a dual floater hybrid system consisting of a floating breakwater and an oscillating-buoy type wave energy converter (WEC). The new model was verified with published experimental results. The differences between the hydrodynamic performance of the hybrid system, a single WEC and a single breakwater were compared. The effects of the wave resonance in the WEC-breakwater gap and the geometrical parameters on the performance of the asymmetric WEC were also studied. It was found that the hybrid system demonstrated both better wave attenuation and wave energy extraction capabilities at low wave frequencies, i.e., wider effective frequency. The forces on the breakwater were generally reduced due to the WEC. Wave resonance in the narrow gap has an adverse effect on the hybrid system with an asymmetric WEC, while a beneficial effect with a symmetric WEC. The wave energy conversion efficiency of hybrid system can be improved by increasing the draft and width of the WEC and decreasing the distance between the WEC and the breakwater. The findings of this paper make wave energy economically competitive and commercial-scale wave power operations possible.

Hydrodynamic Performance of a Hybrid System Combining a Fixed Breakwater and a Wave Energy Converter: An Experimental Study

“…In the theory for linear waves, the energy conversion efficiency is expected to be independent of the incident wave height H i . However, the nonlinearity of wave interaction with floating bodies is closely related to the value of wave steepness [14]. For waves with a large value of H i /L i , strong nonlinear wave deformations occur during the wave-structure interaction and the consequent energy loss significantly affects the energy conversion efficiency.…”

“…Detailed experiments were undertaken to investigate the heave-response-amplitude operator, the wave force on the WEC devices, and the transmission coefficient of the breakwater-WEC system. More recently, Zhang et al [14] proposed a dual-floater hybrid system consisting of a floating breakwater and an oscillating-buoy type WEC and investigated its performance using a numerical wave tank. It was found that the wave energy conversion efficiency of the hybrid system could be improved by increasing the draft and width of the WEC and decreasing the distance between the WEC and the breakwater.…”

Motion Response and Energy Conversion Performance of a Heaving Point Absorber Wave Energy Converter

“…As introduced in Motion Equation of Wave Energy Converter section, the total damping λ vist,3 can be obtained through the free decay motion of the WEC, simulating using the Star-CCM+ (need a reference). Star-CCM+ has been used in studying the interaction of waves and a two-dimensional floating body (Zhang et al, 2020a;Zhang et al, 2020b), and the free decay motion of a three-dimensional floater (Chen et al, 2018b). Their accuracy has been validated with the experimental results.…”

“…Their accuracy has been validated with the experimental results. The detailed setup can be found in Zhang et al (2020a;2020b) and Chen et al (2018b).…”

“…Jin and Patton (2017) studied three cylindrical floaters by LS-DYNA (LS-dynamic finite element analysis), and the results demonstrated that the rounded-and conical-bottom floaters had less viscous damping than that with the flat-bottom. Zhang et al (2020a) selected four single-floater integrated systems with different bottom shapes and studied the effect of bottom shape on the hydrodynamic performance of the integrated system. However, the computational cost of detailed CFD simulations is high, partly due to the requisite large computational meshes.…”