Dual-frequency power capture performance and harvesting source identification of a spring pendulum buoy wave energy converter

The contradiction between the narrow power capture bandwidth and the wave energy spectral distribution leads to the suboptimal generating efficiency of wave energy buoys in real sea. A novel spring pendulum buoy was proposed to use its dual-frequency performance, stemming from two motion degrees of freedom, for efficient harvesting in bimodal Ochi-Hubble spectral seas with wind wave and swell. A novel energy harvesting source identification method was proposed to assess its power capture performance from wind wave and swell respectively. Validation was conducted through a wave tank experiment. Dual-frequency power capture performance was analyzed, with a particular focus on perspectives from the degree of freedom and the frequency distribution. Effects of structure coefficients were analyzed. Results showed that the spring pendulum buoy has a significant dual-frequency power capture characteristic and a significant broader high-efficiency frequency bandwidth. The combination of two degrees of freedom is the main reason for the dual-frequency power performance. The spring swing arm only enhances the dual-frequency power capture of rotation. The PTO damping's effect becomes more complicated because of the shifting motion balance position. This dual-frequency characteristic effectively enhances its power capture in bimodal Ochi-Hubble waves, particularly improving the power capture from high-frequency wind waves.