Jun 15, 2022 | offshore marine news

Acta Marine has placed an order for two Ulstein Twin X-Stern Construction Service Operation Vessels (CSOVs) to a new SX216 design from Ulstein Design & Solutions, with options for two additional vessels, to be delivered with dual-fuel methanol/diesel power plants.

Rob Boer, Acta Marine, said: “We are pleased to build on our existing relationship with Ulstein Design & Solutions for our next generation Construction Service Operation Vessels combining Acta Marine’s operational experience and Ulstein’s innovative design capabilities.”.

The Ulstein Twin X-Stern concept has been described as a ship with two sterns and four main propeller units: two at each end. The X-Stern at each end results in high levels of operability with either end towards the weather, without limitation on vessel speed.

The Twin-X-Stern designs claim improved fuel efficiency, increased dynamic positioning (DP) capability and manoeuvrability, reduced motions and reduced noise. The Twin X-Stern offers more flexibility regarding the choice of propeller type, a bi-symmetric hull shape and propulsion setup with fewer propulsion units is possible.

The CSOVs for Acta Marine will have a hybrid power solution, with green methanol intended as the main source of energy. The Dual-Fuel engines are supported by a battery package, integrated into the vessel in such a way as to allow the most fuel-efficient modes of operation, reduced maintenance costs and reduced emissions.

Erwin Jager, Ulstein Design & Solutions, said: “Being a leading actor in the renewable energy business, it is paramount to be prepared for a future where zero or low-carbon fuels are available. Acta Marine has a strong wish to offer their clients the largest possible reduction of emissions straight from delivery of the vessels. Therefore, these vessels required a practical and timely available solution to reduce their carbon footprint from the outset of the design. The carbon footprint of Marine Gas Oil (MGO) makes MGO non-sustainable as the sole choice for the future. Currently, the decision on what alternative fuel to focus on can be overwhelming as it is affected by many factors internally and externally. Through a decision support process, developed by Ulstein to guide owners in the myriad of choices to be made, a matrix of alternative fuels has been evaluated towards a set of criteria unique to the shipowner and the business case. Through this process, methanol came out as the winner for this project, with the best overall score. The energy density and storage of methanol is favourable, it is an accessible energy source, and there are dual-fuel engines available in the market that can handle both methanol and diesel.”

As soon as methanol had been chosen as an alternative energy source, Ulstein Design & Solutions started to adapt the design, implementing the methanol bunkering, tank and system layouts on a conceptual level.

The SX216 design has a length of 89.9m, a beam of 19.2m and accommodates up to 135 personnel. 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. Ulstein has previously developed and built two CSOVs for the Netherlands-based shipowner. The new vessels will be constructed at Tersan Shipyard.

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