Motion Suppression of a Floating Offshore Wind Turbine Using Heaving Point Absorbers: A Case Study in Australia

Abstract

Abstract Hybrid platforms composed of a floating offshore wind turbine (FOWT) and heaving point absorbers (PAs) can be a promising solution to reduce project costs while improving the quality of energy and ocean space utilisation. Although this hybrid platform idea is attractive, wave energy converters (WECs) may transfer part of their energy to the FOWT via motion if the devices and their respective power-take off (PTO) systems are not properly designed, leading to undesirable loads. Based on that, an alternative option is the use of WECs to reduce the FOWT platform motions, while absorbing wave energy. This approach is particularly important in locations where both resources are abundant, such as in Australia, where the hybrid solution may extend the platform’s lifetime. In this general context, this work aims to investigate the use of PAs as a motion suppression device. The hybrid platform is assumed to be subject to realistic environmental conditions: turbulent wind (temporal and spatial effects) and irregular waves. The numerical model is built in the frequency domain, and important sources of nonlinearities are estimated using statistical linearisation. The performance of the hybrid platform is compared against the standalone FOWT for an offshore site in Sydney, Australia. Results demonstrate that depending on the PTO configuration, the hybrid platform has a superior response compared to the standalone FOWT, suppressing the horizontal nacelle acceleration by around 8% while extracting an additional 30 kW from waves.