Multivariable design optimization for adaptive resonance of a surface riding wave energy converter

Since the ocean waves feature irregular waves varying over time, a wave energy converter with adaptive resonance, which feasibly changes the natural frequency for different sea states, is considered. To find its optimum design, multi-dimensional parametric optimization is formed in sequence of setting ranges of submerged geometry for hydrodynamic performance, finding design specifications including the generator for maximum resonance peaks, and locating the natural frequency for individual sea states to achieve the adaptive resonance that converts the maximum annual mechanical power for the given geometry. The multivariable design optimization is performed for a kilowatt-scale Surface-Riding Wave Energy Converter, which controls the pitch natural frequency through relocating a mass vertically. The optimized design presents that the adaptive resonance improves the mechanical power conversion up to 11 times compared to the conventional fixed resonance design. Furthermore, the adaptive resonance for diverse wave spectra indicates that the optimum natural frequencies for individual sea states, maximizing the annual mechanical power conversion, do not coincide with the waves' peak or energy period. The second-order wave loads entails further change of the optimum natural frequency resulting in subsequent 10 times performance improvement for severe sea states with high peak periods.