Performance estimation of resonance-enhanced dual-buoy wave energy converter using coupled time-domain simulation

This paper presents the modeling methodology and performance evaluation of the resonance-enhanced dual-buoy WEC (Wave Energy Converter) by HEM (hydrodynamic & electro-magnetic) fully-coupled-dynamics time-domain-simulation program. The numerical results are systematically compared with the authors' 1/6-scale experiment. With a direct-drive linear generator, the WEC consists of dual floating cylinders and a moon-pool between the cylinders, which can utilize three resonance phenomena from moon-pool dynamics as well as heave motions of inner and outer buoys. The contact and friction between the two buoys observed in the experiment are also properly modeled in the time-domain simulation by the Coulomb-friction model. Moon-pool resonance peaks significantly exaggerated in linear potential theory are empirically adjusted through comparisons with measured values. A systematic comparative study between the simulations and experiments with and without PTO (power-take-off) is conducted, and the relative heave displacements/velocities and power outputs are well matched. Then, parametric studies are carried out with the simulation program to determine optimum generator parameters. The performance with various wave conditions is also assessed.

Highlights:
1. Dual-cylinder wave energy converter with moon-pool is designed to use three resonances.
2. Interaction between the dual cylinder and the linear generator is solved in time domain.
3. The proposed simulation model correlated to the experiments provides coincided results with experiments.
4. Moon-pool and guiding mechanisms between the cylinders influence dynamic response and power notably.
5. Optimum parameters of the linear generator are found using the correlated model.