Extreme Responses of An Integrated System with A Semi-Submersible Wind Turbine and Four Torus-Shaped Wave Energy Converters in Different Survival Modes

Offshore wind power is a kind of important clean renewable energy and has attracted increasing attention due to the rapid consumption of non-renewable energy. To reduce the high cost of energy, a possible try is to utilize the combination of wind and wave energy considering their natural correlation. A combined concept consisting of a semi-submersible wind turbine and four torus-shaped wave energy converters was proposed and numerically studied under normal operating conditions. However, the dynamic behavior of the integrated system under extreme sea conditions has not been studied yet. In the present work, extreme responses of the integrated system under two different survival modes are evaluated. Fully coupled time-domain simulations with consideration of interactions between the semi-submersible wind turbine and the torus-shaped wave energy converters are performed to investigate dynamic responses of the integrated system, including mooring tensions, tower bending moments, end stop forces, and contact forces at the Column-Torus interface. It is found that the addition of four tori will reduce the mean motions of the yaw, pitch and surge. When the tori are locked at the still water line, the whole integrated system is more suitable for the survival modes.