A gangway is approaching an offshore wind substructure.
Photo: UPTIME International AS

Improved analysis methods for safe personnel transfer to floating offshore wind turbines

For floating offshore wind turbines in harsh environmental areas, the safety of personnel transferred from supporting vessels to the installations is of concern. Service vessels equipped with motion-compensated gangway systems are known to represent the state of the art in providing access to offshore wind turbines.

Accurately modelling the motion behaviour of floating bodies in an environment of waves, wind, and current is crucial for precise performance predictions. The traditional efficient way of performing operability studies is to calculate vessel motions, responding to wave excitation forces, by linear first-order wave-induced forces in the global coordinate system. This procedure is only applicable when calculating operations towards stationary, bottom-fixed landing points. For simulations towards floating wind turbines, the motion of the vessel and the floating wind turbine structure must be simulated separately using two discrete Response Amplitude Operators (RAOs) and solved together in the time domain.

To enable the industry to use efficient and well-known frequency-domain simulations further, the data from the two RAOs are combined as one relative motion RAO, describing the motions of the two bodies in one transfer function. This innovation allows the industry to use the same operability assessment strategy for future floating wind projects. It provides a cost-effective simulation method for making quick decisions in ensuring safe and effective personnel transfer to floating offshore wind turbines. This innovation is currently at TRL 4.