Multi-objective optimization and performance analysis of a 10 MW offshore wind-wave hybrid system with built-in wave energy converters

Abstract

Integrating wave energy converters (WECs) into floating offshore wind turbines (FOWTs) offers the potential to reduce both power generation costs and platform motions. Placing WECs within the hollow side columns of the wind turbine platform represents a novel approach, providing protection against direct wave impact and corrosion. However, the mechanisms and performances of such hybrid systems remain unclear. In this study, a novel wind-wave hybrid system is proposed and investigated, consisting of a 10 MW OO-STAR type platform with built-in WECs. A frequency-domain model based on potential flow theory is developed, and a multi-objective optimization framework using the NSGA-II algorithm is applied to optimize the power take-off (PTO) parameters. Results indicate that global optimization across operational sea-state ranges can effectively mitigates abnormally large pitch motions in specific period ranges, thereby reducing the maximum pitch response across all sea states and broadening the energy absorption bandwidth. By introducing the metric of annual average power generation per unit mass, the economic efficiency of the system is further enhanced. Moreover, the mechanisms by which the PTO parameters influence motion responses and power generation performance of the hybrid system are revealed. These findings provide practical guidance for design and application of wind-wave hybrid systems.