In this paper, the operability of an Offshore Service Vessel (OSV) is looked into for different heading orientations of the vessel. Traditionally, the OSV heading orientation has been into the predominant current direction to prevent large beam current forces and thruster utility. However, such an orientation can lead to unfavourable wave headings which can cause large first order motions making it difficult to operate the gangway on board the vessel. Hydrodynamic time domain simulations were run for 1-year of hindcast weather data from an operational wind farm site in the Netherlands for different OSV heading orientations. The results of the simulations can be used to optimize the OSV heading strategy and increase uptime, reduce waiting time and energy loss associated to this waiting time.

Feeder vessels are one of the solutions being considered to facilitate Jones Act-compliant installation of offshore wind turbines on the US outer continental shelf (OCS). Feeder vessels transport wind turbine components from US ports to offshore locations and position next to an installation vessel, where the components are then lifted off using a crane on the installation vessel. The lifting operation is a highly critical and transient process. A successful lift depends on the lifting system's capability, the feeder vessel's performance, environmental conditions, operational processes and other factors. In 2021, the National Offshore Wind Research and Development Consortium (NOWRDC) initiated Project #107, Comparative Operability of Floating Feeder Solutions, that was undertaken by MARIN, ABS and Saint James Marine. The project primarily entailed computer simulations of offshore wind turbine component lifts and the development of comparative operability assessment procedures for floating feeder solutions. Time domain simulations were used to model the lifting process and results were analyzed relating to wind turbine component accelerations, loads on the lifting system and the re-hit of wind turbine components with the feeder vessel. The study has demonstrated that the combination of time-domain analysis for lifting simulation and frequency-domain analysis for feeder vessel motions can be an effective approach to comparatively analyze a wide range of feeder solutions. Comparative weather downtime and seasonal utilization can also be effectively derived. This paper describes the development process of and provides recommendations for assessing the operability of offshore wind feeder vessels.

The U.S. plans to install 30GW of offshore wind by 2030. However, the lack of Jones-Act compliant installation vessels means that alternative installation strategies will have to be used in the near to mid-term. One such strategy is to use Jones-Act classed barges or purpose built ships to transport Wind Turbine Generator (WTG) components from port to the offshore location where a foreign vessel can install them. This paper uses numerical simulations to derive the uptime of such an operation for different feeder solutions.

The U.S. plans to install 30GW of offshore wind by 2030. However, the lack of Jones-Act compliant installation vessels means that alternative installation strategies will have to be used in the near to mid-term. One such strategy is to use Jones-Act classed barges or purpose built ships to transport Wind Turbine Generator (WTG) components from port to the offshore location where a foreign vessel can install them. This paper uses numerical simulations to derive the uptime of such an operation for different feeder solutions.

The use of motion compensated equipment has become more frequent in modern DP operations, especially the ones related to the installation, maintenance and decommissioning of offshore wind turbines. In these operations, while low-frequency motions are compensated by DP systems, wave-frequency motions are compensated by gripper frames, heave compensators, hexapods, gangways and other type of motion compensated equipment. A study was performed to investigate if the coupling of a dynamic positioning system with a motion compensation device could improve the accuracy and efficiency of offshore motion compensated operations. The reference case consisted of the positioning of a payload, hanging on a ship-mounted crane, by means of a single horizontal active tugger line and the ship's DP system. Four controllers – consisting of two levels of awareness and two tuning conditions – were designed and implemented in a numerical model. The four strategies were then evaluated in terms of position offsets and actuator usage under a number of sea-states. Results demonstrated that coupled controllers are able to decrease the position deviations of the motion compensated object and decrease the usage of the motion compensation device. The paper describes the control strategies, numerical models and results of the simulations.