Sensitivity Analysis of a Floating Hybrid Wind-Wave System to Wave Energy Converter Parameters

Abstract Floating hybrid wind-wave systems combine floating offshore wind platforms and wave energy converters (WECs) to achieve a cheaper energy cost by utilising two different technologies. In such systems, WECs should be appropriately designed and tuned for a particular floating platform and environmental conditions so as not to introduce excessive wind turbine motion and loads while harvesting wave power. This paper considers a 5-MW OC4-DeepCwind semi-submersible platform combined with three spherical WECs and aims to identify what WEC parameters play the most important role in the dynamics of the hybrid wind-wave system. A thorough sensitivity analysis is conducted focusing on wave energy power maximisation and nacelle horizontal acceleration, while investigating the hybrid platform response and their potential effects. For the hybrid platform investigated, the results demonstrate that the WEC radius has a more significant effect on the platform dynamics and wave energy power output than the distance from the WECs to the platform. Depending on the objective function, WECs can contribute up to 10% of the wind turbine power while not increasing the nacelle acceleration. Moreover, WECs have the capability to significantly reduce (up to 50%) the wind turbine nacelle acceleration, and reduce/maintain lower levels of heave and pitch motion. Overall, the largest WECs placed closest to the platform are the most promising candidates for hybridisation with a semi-submersible platform in terms of power output and suppressing the platform motion, while the objective function of the PTO system should focus on the minimisation of the nacelle horizontal acceleration to have additional benefits of motion suppression.