Negative Stiffness Mechanism on An Asymmetric Wave Energy Converter by Using A Weakly Nonlinear Potential Model

Salter's duck, an asymmetrical wave energy converter (WEC) device, showed high efficiency in extracting energy from 2D regular waves in the past; yet, challenges remain for fluctuating wave conditions. These can potentially be addressed by adopting a negative stiffness mechanism (NSM) in WEC devices to enhance system efficiency, even in highly nonlinear and steep 3D waves. A weakly nonlinear model was developed which incorporated a nonlinear restoring moment and NSM into the linear formulations and was applied to an asymmetric WEC using a time domain potential flow model. The model was initially validated by comparing it with published experimental and numerical computational fluid dynamics results. The current results were in good agreement with the published results. It was found that the energy extraction increased in the range of 6% to 17% during the evaluation of the effectiveness of the NSM in regular waves. Under irregular wave conditions, specifically at the design wave conditions for the selected test site, the energy extraction increased by 2.4%, with annual energy production increments of approximately 0.8 MWh. The findings highlight the potential of NSM in enhancing the performance of asymmetric WEC devices, indicating more efficient energy extraction under various wave conditions.