Ulstein Introduces New U-STERN Offshore Wind Vessel Design

April 24, 2023, by Adnan Memija

Ulstein Design & Solutions BV has introduced its patent-pending U-STERN offshore wind installation vessel design for transporting, upending, and installing large monopiles on DP.

According to the developer, the U-STERN enables longitudinal storage of monopiles and upending in the ship’s centre line.

This should allow the ship to head into the waves during the installation process, minimising ship motions, and fuel consumption, while the U-STERN provides shielding from the waves.

Combining the U-STERN with transverse and longitudinal skidding systems, offshore lifts for monopiles are eliminated, said Ulstein, as the main crane is only used to support the upending and lowering of the foundations.

According to Ulstein, the U-Stern looks like a simple recess in the stern, “but is much more than that” added Ko Stroo, product manager/lead naval architect in Ulstein Design & Solutions BV.

“The shape and location of the recess are finely tuned with CFD (Computational Fluid Dynamics) and motion analysis to make it work in harmony with the crane and mission equipment“, said Stroo.

The company outlines that U-STERN has significant benefits over “traditional” monopile installation on the side of the vessel.

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According to Ulstein, the benefits are increased operability due to a 25 per cent reduction in motions, excellent wave shielding in the ‘moonbay’ and controlled upending of monopiles; 50 per cent power reduction in Dynamic Positioning (DP) operations due to weather vaning; avoiding port (and offshore) related challenges connected to transverse monopile transport and upending; and safer lifting operations offshore.

“The U-STERN is however not a ‘one-trick pony’, as the vessel is also suitable for jacket installation and other heavy lift installation work. In the past months, we have presented the U-STERN to major contractors and operators, many recognizing this as the most viable solution for installing the next-generation monopile foundations”, said Ulstein.