Offshore wind: World’s largest HLV will feature Ulstein U-stern

Image: Penta Ocean

Japan’s Penta-Ocean Construction has signed a shipbuilding contract with Seatrium covering the construction of what it says will be the world’s largest heavy lift vessel. To be used for the installation of offshore wind turbine monopile foundations, it will feature a fully revolving 5,000-tonne crane and the Ulstein U-stern.

With a U-shaped notch at the stern, the HLV is designed to upend a monopile being stored lengthwise on the vessel using the 5,000-tonne crane and an upending system with a gripper that enables installation directly at the notch. Since the installation is performed at the stern, the HLV’s hull shields its operation from waves and currents, thereby minimizing ship motions.

Ulstein Design & Solutions has been awarded the contract for the hull design, while Huisman Equipment will build the on-deck equipment, which includes the fully revolving 5,000-tonne crane and the monopile upending system with gripper. Completion is scheduled for May 2028, with operation anticipated in the fall of 2028.

Huisman says Its 5,000 tonne active heave-compensated tub mounted crane features a dual main hoist and universal quick connector, enabling efficient, safe tool changes to reduce cycle time and safety risks. Key advantages of the low weight tub mounted crane include a compact tail swing for deck space optimization, no counterweight, full revolving capacity, and an in-house produced slew bearing.

The motion compensated pile gripper is specifically designed for the installation of large-diameter, variable-length monopiles over the vessel’s unique U-shaped stern. With the monopiles being stored lengthwise on the vessel, the integrated upending system enables direct handling from storage to installation.

Other features

• Capable of installing monopiles weighing up to 3,000 tons
• Multiple monopiles can be loaded and transported, enabling efficient construction
• Equipped with a ClassNK DPS2 dynamic positioning system featuring nine thrusters with a total output of 25,000 kW or more) ensures high positioning capability
• A battery storage system will be installed, and the vessel will be methanol ready

Ulstein says that the award of its contract follows feasibility and concept studies in 2023 based on its HX118 with the U-stern. The vessel will also feature the X-bow, and at 215 meters long and 56 meters wide, will be the largest X-bow vessel yet built .

HOW THE U-STERN WORKS

The U-stern features longitudinal storage and upending of monopiles along the ship’s centerline. This innovation enables the installation of longer monopiles without overhanging the ship’s sides and allows the vessel to face the waves during the installation, minimizing ship motions and fuel consumption.

The design is being developed at Ulstein’s Rotterdam office, with significant support from Ulstein Poland during the Basic Design phase.

“We are honored that Penta-Ocean Construction chose us to design their new heavy lift vessel. This project represents a powerful collaboration between Penta-Ocean Construction, Ulstein and Huisman to design this most capable monopile installation vessel,” says Ko Stroo, lead designer at Ulstein Design & Solutions B.V. “As the project moves forward with its construction at the Seatrium shipyard, Singapore, we remain committed to supporting the parties throughout the construction phase.”