Nonlinear Modeling and Verification of a Heaving Point Absorber for Wave Energy Conversion

Although the heaving point absorber (PA) concept is well known in wave energy conversion research, few studies focus on appropriate modeling of nonlinear fluid viscous and mechanical friction dynamics. Even though these concepts are known to have nonlinear effects on the hydrodynamic system, most research studies consider linearity as a starting point and in doing so have a weak approach toward modeling the true dynamic behavior, particularly close to resonance. The sole use of linear modeling leads to limited ability to develop control strategies capable of true power capture optimization and suitable device operation. Based on a 1/50 scale cylindrical heaving PA, this research focuses on a strategy for hydrodynamic model development and experimental verification. In this study, nonlinear dynamics are considered, including the lumped effect of the fluid viscous and mechanical friction forces. The excellent correspondence between the derived nonlinear model and wave tank tested PA behaviors provides a strong background for wave energy tuning and control system design.