Numerical analysis and performance optimization of a submerged wave energy converting device based on the floating breakwater

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A submerged wave energy converting device, based on the proton-type floating breakwater, has been studied under regular waves in the present study. In order to assess the performance of the developed Wave Energy Convertor (WEC), a numerical simulator has been built based on the Navier-Stokes solver. Making use of the laboratory measurements, the numerical model has been proved to be a reliable tool for reproducing wave deformations and the dynamics of the floating energy device. Then, the model was employed to test the sensibility of the proposed WEC performance to changes in some variables under regular waves: wave period, Power Take Off (PTO) damping, and spring constant. Three damping functions for the PTO system were employed, namely, constant value, step function, and sine function. From numerical estimations, it can be concluded that the PTO damping function and the properties of springs play important roles in effectively harnessing the wave energy. The highest energy conversion ratio can be up to approximately 17%, either by using a relatively large PTO damping or by using a smaller PTO damping but with the help of springs. A tuning strategy making use of the supplementary springs was also suggested to maintain a high energy capture width for the present WEC in changing waves. Moreover, the efficiency of the developed WEC was also discussed when subjected to less energetic water waves, which was important for a smooth power output of the device under various wave conditions.