Abstract
Majority of the wave energy converters (WEC), especially buoyancy-based point absorbers, are designed to operate in high sea states maximizing energy extraction. Most WEC simulation tools use linear wave theory to analyze the wave field, which could lose accuracy under high sea state conditions. A parametric study is conducted to investigate the effects of the nonlinear wave propagation modeling on WEC responses. The nonlinear Schrödinger (NLS) equation was implemented to develop a nonlinear propagation model. The NLS-based model captures cubic nonlinear phenomena such as extreme sea conditions caused by modulation in wave envelope, which is a critical factor in the survivability of WEC systems. Also, to improve response analysis, mooring/cable system dynamics were represented with a bending stiffness module (MDB). This study was completed using a Reference Model 3 (RM3) WEC system in the National Renewable Energy Laboratory’s (NREL) Wave Energy Converter Simulator (WEC-Sim) in MATLAB. New modules have been built as open-source code to be used in conjunction with the latter, giving more modeling options to the end user and help developing more realistic assessments of a WEC or other floating system in their chosen sea state and location. The model was first subjected to an arbitrary regular wave to prove the interoperability of the two modules and measure initial effectiveness. The presented analysis highlights the differences in the response of the RM3’s system from existing models based on linear wave theory that do not include NLS and MDB in their calculations.