With the offshore wind industry facing significant installation challenges due to the increasing size of monopile foundations, Norwegian ship designer Ulstein Design & Solutions BV says that it has introduced a safer, smarter and more competitive solution for their transportation, upending and installation using dynamic positioning.
According to the company, its U-STERN system enables longitudinal storage of monopiles and upending in the ship centreline. This allows the ship to head into the waves during the installation process, thereby minimising ship motions and fuel consumption, while still providing shielding from waves.
Ulstein adds that by combining the U-STERN with transverse and longitudinal skidding systems, offshore lifts for monopiles are eliminated, as the main crane is only used to support the upending and lowering of the foundation.
The U-STERN looks like a simple recess in the stern. “But it is much more than that,” explains Ko Stroo, lead naval architect at Ulstein Design & Solutions. “The shape and location of the recess are finely tuned with CFD and motion analysis to make it work in harmony with the crane and mission equipment.”
Stroo adds that more than two years of R&D have enhanced Ulstein’s understanding of how to improve the dynamics associated with DP monopile installation. This, he says, has resulted in the U-STERN having significant benefits over ‘traditional’ monopile installation on the side of a vessel, including increased operability due to a 25 % reduction in motions and 50% power reduction in DP operations.
The U-STERN system is also suitable for jacket installation and other heavy lift installation work.
