Abstract
Wave energy is favored by more and more people because of its wide distribution, pollution-free, renewable and many other advantages. Among numerous wave energy converting devices, the converters using floating breakwaters are recognized to be quite promising as the construction and maintenance cost can be shared. In this study, a shoreline wave energy converter (WEC) is proposed which consists of a floating breakwater arranged along the wave direction and restricted to only have vertical degree of motion. Making use of the motion of breakwaters, a dynamo is able to convert the wave power to electricity. At the same time, the incoming waves can be attenuated due to the complex interaction between waves and the floating structure. A scale model was built in the laboratory at Hohai University, and then employed to investigate the performance of developed wave energy device. In the physical model, dynamos and resistance were employed as the power take-off (PTO) system, and the instantaneous output power could be calculated using the measured data. Experimental results show that the resonance state of float plays an important role for the wave energy extraction, and the hydrodynamic efficiency of the device under the resonance state can be up to 41.8% for single breakwater, counting in the internal energy converted by the dissipative force. When subjected to shorter waves, the PTO damping encourages the wave reflection; whereas, more wave energy is dissipated or transformed to power for longer waves. Meanwhile, the PTO damping is also a negative factor for the wave overtopping reduction as the motion of float may be restrained considerably. Last but not the least, the PTO load is proved to be a significant parameter for the optimization the output power, and a strategy must be found to achieve the best power conversion under the dominant wave conditions.
