Wave Extraction and Attenuation Performance of An Edinburgh Duck Wave Energy Converter

Edinburgh Duck wave energy converter(ED WEC)has excellent energy extraction performance and shows a great potential to integrate with other marine structures.This paper aims to investigate its wave energy extraction performance as a WEC and wave attenuation performance as a protection method for shoreline or marine structures.The wave and ED WEC interactions in regular waves are modeled using the Star-CCM+software and verified by comparisons with published experimental results.The motion response,energy conversion efficiency,and transmission coefficient of the ED WEC with different attack angles,rotation center,and incident wave heights are investigated.Results indicate that the ED WEC with an attack angle of 42°and a rotation center of 0.55 m below the mean water line can achieve both good wave energy extraction and wave attenuation performances.The wave energy extraction and wave attenuation performance of the ED WEC decrease significantly with the increase of wave nonlinearity characterized by the wave steepness.This paper can guide the practical application of the ED WEC at the early stage of design.

Wave Extraction and Attenuation Performance of A Hybrid System of An Edinburgh Duck WEC and A Floating Breakwater

Installing the Edinburgh Duck Wave Energy Converter(ED WEC)on a floating breakwater provides a potential solution to reduce costs and improve the reliability of the ED WEC.To investigate the interactions between the ED WEC and the breakwater,a two-dimensional numerical model of a hybrid WEC-breakwater system is established based on Star-CCM+Computational Fluid Dynamics(CFD)software.The wave energy extraction performance,wave attenuation performance,and wave forces on the breakwater of the hybrid system are compared with those of the corresponding single device.The effects of the initial attack angle,the distance between the WEC and the breakwater,and the incident wave height on the pitch motion,energy conversion efficiency,transmission coefficient,and wave forces on the breakwater of the hybrid system are analyzed.The results indicate that combing the ED WEC with a breakwater can improve the energy extraction performance of the ED WEC and reduce the wave forces on the breakwater in shorter-period waves.The conversion efficiency of the hybrid system with the initial attack angle of 42°is the largest in shorter-period waves,but is reduced with the increase of initial attack angle in longer-period waves.The wave attenuation performance of the hybrid system is determined by the draft of the breakwater.The distance between the WEC and the breakwater has little effect on the hybrid system.Wave energy extraction of the ED WEC of the hybrid system decreases significantly with the increase of the incident wave height.