When the vessel’s main function is walk-to-work (W2W) services in the offshore renewable sector, a heightened stern can operate either way, thus facilitating on-site DP positioning. This is the idea behind the TWIN X-STERN™ concept vessel from ULSTEIN, which also includes new thoughts on propulsion, bridge, gangways and cranes.
With an X-STERN at each end, the vessel is symmetrical, with a continuous large work deck and cranes on either side of the bridge. The X-STERN is heightened by one deck and gives shelter to the deck area. The large deck space can be used for transporting equipment, containers and spare parts.
"By moving wind farms further from shore, the turbines can increase in size. The TWIN X-STERN vessels will be ideal for maintaining large-scale wind farming activities far from shore." Øyvind Gjerde Kamsvåg, Chief designer
The asymmetrical bridge can be made of composite material and is placed midship, diagonally above the work deck. The operating bridge is placed as a lookout platform on both the starboard and port sides, close to the ramp on either side, giving a full overview of the nearest ramp as well as the complete work deck area. The vessel can be equipped with a safe transferral ramp on both the star board and port side of the bridge. Additionally, a large W2W ramp for oil and gas rigs can be integrated into the vessel for more flexibility. The helideck is placed on top of the bridge, where the movements are at the lowest.
In this concept, ULSTEIN has been exploring new crane technology, such as the patent-pending ULSTEIN COLIBRI™, an electric-driven solution for motion compensation at the crane tip.