Hydrodynamic performance of a floating breakwater as an oscillating-buoy type wave energy converter

Combined floating breakwater and wave energy converter systems have the potential to provide a cost-effective solution to offshore power supply and coastal protection. This will make wave energy economically competitive and commercial-scale wave power operations possible. This paper investigates the hydrodynamic features of wave energy converters that meet the dual objectives of wave energy extraction and attenuation for such a combined system. A two-dimensional numerical model was established using Star-CCM+ commercial software based on viscous Computational Fluid Dynamics theory to investigate the hydrodynamic performance of an oscillating buoy Wave Energy Converter (WEC) type floating breakwater under regular waves. The model proposed in this paper was verified with published experimental results. The hydrodynamics of symmetric and asymmetric floaters were investigated to demonstrate their wave attenuation and energy extraction performance, including square bottomed, triangular bottomed (with and without a baffle plate), and the Berkley Wedge. The asymmetric floaters were found to have higher power conversion efficiency and better wave attenuation performance, especially the Berkeley Wedge bottom device and the triangular-baffle bottom device. The triangular-baffle bottom device with a simpler geometry achieved similar wave attenuation and energy extraction performance characteristics to that of the Berkeley Wedge device. The maximum energy conversion efficiency of the triangular-baffle bottom floater reached up to 93%, an impressive WEC device among many designs for wave energy conversion. There may be a great potential for this newly proposed triangular-baffle bottom WEC type of floater to be an ideal coastal structure for both coastal protection and wave energy extraction.

[1]  Bin Teng,et al.  Numerical investigation of wave radiation by a vertical cylinder using a fully nonlinear HOBEM , 2013 .

[2]  U. Piomelli,et al.  Large-Eddy Simulation of Transition to Turbulence in Boundary Layers , 1997 .

[3]  Y. Goda,et al.  ESTIMATION OF INCIDENT AND REFLECTED WAVES IN RANDOM WAVE EXPERIMENTS , 1976 .

[4]  Ronald W. Yeung,et al.  The “Berkeley Wedge”: an asymmetrical energy-capturing floating breakwater of high performance , 2014 .

[5]  Conghao Xu,et al.  A dual-functional wave-power plant for wave-energy extraction and shore protection: A wave-flume study , 2018, Applied Energy.

[6]  Chang-Kyu Rheem,et al.  Wave energy device and breakwater integration: A review , 2017 .

[7]  Mohammad-Reza Azizi,et al.  Numerical simulation of vertical water impact of asymmetric wedges by using a finite volume method combined with a volume-of-fluid technique , 2018, Ocean Engineering.

[8]  Ugo Piomelli,et al.  Large-eddy simulation: achievements and challenges , 1999 .

[9]  Ming Zhao,et al.  Analytical investigation of hydrodynamic performance of a dual pontoon WEC-type breakwater , 2017 .

[10]  Heng-xu Liu,et al.  Hydrodynamic analysis and shape optimization for vertical axisymmetric wave energy converters , 2016 .

[11]  Xuanlie Zhao,et al.  Hydrodynamic Investigation of an Oscillating Buoy Wave Energy Converter Integrated into a Pile-Restrained Floating Breakwater , 2017 .

[12]  L. Wu,et al.  Resonance of the roll motion of a two dimensional barge induced by triple frequency wave force , 2017 .

[13]  J. Zang,et al.  Geometrical Evaluation on the Viscous Effect of Point-Absorber Wave-Energy Converters , 2018, China Ocean Engineering.

[14]  Pasquale Contestabile,et al.  Wave loadings acting on innovative rubble mound breakwater for overtopping wave energy conversion , 2017 .

[15]  Bruce L. McCartney.  Floating Breakwater Design , 1985 .

[17]  John D. Fenton,et al.  A Fifth‐Order Stokes Theory for Steady Waves , 1985 .

[18]  Liang Zhang,et al.  Hydrodynamic response and power efficiency analysis of heaving wave energy converter integrated with breakwater , 2019, Energy Conversion and Management.

[19]  J. Falnes,et al.  A resonant point absorber of ocean-wave power , 1975, Nature.

[20]  G. Iglesias,et al.  Coast/breakwater-integrated OWC: A theoretical model , 2019, Marine Structures.

[21]  D. Liang,et al.  Experimental investigation on hydrodynamic performance of a breakwater-integrated WEC system , 2019, Ocean Engineering.

[22]  Almerindo D. Ferreira,et al.  Numerical simulation of regular waves: Optimization of a numerical wave tank , 2018, Ocean Engineering.

[23]  M. Amiri,et al.  How does the free surface affect the hydrodynamics of a shallowly submerged submarine? , 2018, Applied Ocean Research.

[24]  John D. Fenton,et al.  A Fourier approximation method for steady water waves , 1981, Journal of Fluid Mechanics.

[25]  Haigui Kang,et al.  Hydrodynamic performance of a pile-restrained WEC-type floating breakwater: An experimental study , 2016 .

[26]  Johannes Falnes,et al.  A REVIEW OF WAVE-ENERGY EXTRACTION , 2007 .

[27]  D Joslin Ronald,et al.  Large-Eddy Simulation of Transition to Turbulence in Boundary Layers , 1997 .

[28]  Adrian Wing-Keung Law,et al.  An experimental study of a floating breakwater with asymmetric pneumatic chambers for wave energy extraction , 2013 .

[29]  Shili Sun,et al.  Fully Nonlinear Time Domain Analysis for Hydrodynamic Performance of An Oscillating Wave Surge Converter , 2018, China Ocean Engineering.

[30]  G. Iglesias,et al.  The economics of wave energy: A review , 2015 .

[31]  Atilla Incecik,et al.  Experimental study on configuration optimization of floating breakwaters , 2016 .

[32]  Thomas Rung,et al.  Analysis of non-conservative interpolation techniques in overset grid finite-volume methods , 2017 .

[33]  Yang Zhiyin,et al.  Large-eddy simulation: Past, present and the future , 2015 .

[34]  Jie Leng,et al.  An experimental investigation into the wave power extraction of a floating box-type breakwater with dual pneumatic chambers , 2017 .

[35]  Ching-Yun Yueh,et al.  A boundary element model for a partially piston-type porous wave energy converter in gravity waves , 2012 .

[36]  Gregorio Iglesias,et al.  Hydrodynamic performance of a pile-supported OWC breakwater: An analytical study , 2019, Applied Ocean Research.

[37]  Christopher Williams,et al.  Focused waves and wave-structure interaction in a numerical wave tank , 2012 .

[38]  G. Moretti,et al.  Modelling and field testing of a breakwater-integrated U-OWC wave energy converter with dielectric elastomer generator , 2020 .

[39]  D. Ning,et al.  Experimental investigation of breakwater-type WEC composed of both stationary and floating pontoons , 2018, Energy.

[40]  C. Wang,et al.  Review of recent research and developments on floating breakwaters , 2018, Ocean Engineering.

[41]  Dongsheng Qiao,et al.  Hybrid floating breakwater-WEC system: A review , 2019, Ocean Engineering.