US Feeder Solutions for Offshore Wind

Abstract

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.