Ulstein to Design Two More Offshore Wind Vessels for Acta Marine


Ulstein Design & Solutions has signed a contract with Turkey's Tersan Shipyard for two methanol-fuelled ULSTEIN SX216 Construction Service Operating Vessel (CSOV) designs. 

The vessels will be constructed for the Dutch company Acta Marine and will be number 3 and 4 with the TWIN X-STERN solution in the Acta Marine fleet.

The SX216 vessel series has a length of 89,9m, a beam of 19,2m and accommodates up to 135 POB. It has a walk-to-work (W2W) motion-compensated gangway for safe personnel transfer to the turbines, a 3D-motion-compensated crane for cargo transfer, and it can carry a daughter craft for in-farm transfers.

The ship owner Acta Marine has already signed a long-term contract for a 12-year basis with RWE for the two vessels to support North Sea offshore wind farms.

The vessels are expected to begin operation from the Port of Grimsby in early 2025 and 2026.


The TWIN X-STERN vessels have two sterns and two main propeller units at each end. 

"Placing either end towards the weather results in excellent operability without limitation on vessel speed. The TWIN X-STERN solution leads to improved fuel efficiency whilst reducing the motions, which is important for technicians who need quality rest to perform safe operations," Ulstein explained.

According to Ulstein, the TWIN X-STERN offers larger flexibility regarding the choice of propeller type, a bi-symmetric hull shape and propulsion setup with fewer propulsion units is possible.

The hybrid power solution in these vessels, with green methanol intended as the main energy source, has dual-fuel engines supported by a battery package. 

"The system integration allows the most fuel-efficient modes of operation. Combining the fuel-efficient TWIN X-STERN and the dual-fuel methanol/diesel power generators will help reduce the emissions in offshore wind farm operations," Ulstein said.

“We are excited to announce the order of two more Ulstein-designed SX216 SOVs," stated Rob Boer, Managing Director of Acta Marine. "These vessels represent the culmination of extensive research by Acta Marine in combination with Ulstein’s engineering excellence. With the vessel’s advanced features and cutting-edge technology, they will play a pivotal role in supporting the TK and Sofia projects for RWE, providing efficient and reliable services while minimizing environmental impact.”

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