Covering the entire life span of offshore wind farms

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FEATURE

The urgent push for more renewable energy production to achieve climate goals translates into many new offshore wind projects. Simultaneously, ambitious climate goals also call for vessels to be developed with solutions for zero-emission operations.

Many new offshore wind farms are located further from shore, quite often also in deeper waters, rougher conditions and they feature ever-larger wind turbines. This leads to the development of new ships that can handle the new requirements these fields and turbines pose.

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Companies that rely on ocean-going vessels are under pressure to reduce their environmental footprint. In addition to the IMO target, the European Parliament has voted for a similar reduction.

The demand for greener vessels for offshore wind farms is expected to increase with the growth of the offshore wind market, which is projected to reach  USD 1 trillion by 2040.

ULSTEIN provides ship designs, system solutions and services for efficient and reliable marine operations. This includes ship designs for all cycles in the life of the offshore wind farms, with solutions for environmentally friendly vessels to serve the various stages.

“Thinking differently to make the industry even more competitive”

Offshore heavy lift vessels are one of the design areas that Ulstein specialises in. Given the trend in the industry for ever bigger wind turbines, larger installation units will be required for both foundations and wind turbines. With new offshore wind farms also more often being established further from shore, transit times become longer, and the size of vessels must be optimised for these new conditions.

One example is the ‘Subway Alfa Lift’ vessel for Seaway 7. The heavy-lift crane installation vessel with semi-submersible heavy transportation capabilities is the world’s largest, custom-built vessel for offshore wind foundation installation featuring a 3,000-tonne crane and more than 12,300 square metres of available deck space.

From vessels used in survey and seabed preparations to vessels dedicated to installation, service and operation and cable laying, we see a general trend towards larger and therefore often more expensive vessels. Ulstein’s customised 'Alfa Lift' design is a breakthrough of this trend, by applying smarter design principles. Relying on Archimedes’ principle, the 'Alfa Lift' design can achieve higher operational performance compared to existing vessels without compromising the economic performance of the operations.
From vessels used in survey and seabed preparations to vessels dedicated to installation, service and operation and cable laying, we see a general trend towards larger and therefore often more expensive vessels. Ulstein’s customised 'Alfa Lift' design is a breakthrough of this trend, by applying smarter design principles. Relying on Archimedes’ principle, the 'Alfa Lift' design can achieve higher operational performance compared to existing vessels without compromising the economic performance of the operations.

Because of the ‘Subway Alfa Lift’ capacities and capabilities, Seaway 7 has been awarded the transport and installation of monopile foundations and transition pieces for the Dogger Bank wind farms.

“We need new entrants that can think differently and make the industry even more competitive"
Halfdan Brustad, Vice President Equinor’s Dogger Bank

The main deck incorporates a fully automated skidding system, whilst the forecastle deck carries transition pieces and mission equipment. The monopiles that will be installed at Dogger Bank will be amongst the largest ever used on an offshore wind farm. Utilising one single vessel, the foundations will be transported to the offshore site, approximately 130km off the northeast coast of England, and installed in water depths of up to 35 metres. The 216-metre vessel will load out 10 Dogger Bank monopiles and 10 transition pieces for installation at a time thanks to its 48,000-tonne deadweight.

Performing the work of two vessels in one, the ‘Subway Alfa Lift’ is optimising efficiency for the transport and installation of next-generation foundations.

ULSTEIN X-JACK – TURBINE INSTALLATION POWERED BY HYDROGEN

Self-propelled jack-ups are the chosen tool for installing wind turbines as they provide more precision high up when handling the nacelle and turbine blades.

As part of Ulstein’s strategy to offer a complete offshore wind vessel portfolio, Ulstein developed the X-JACK series, now also as zero-emission hydrogen-powered vessels, as an answer to the offshore wind industry’s need for fit-for-purpose, cost-efficient yet future proof wind turbine installation vessels.

The designer's illustration of the ULSTEIN J102 zero-emission wind turbine installation vessel (WTIV). This vessel can operate 75% of the time in zero emission mode. Using readily available technology, the additional cost is limited to less than 5% of the total CAPEX.
The designer's illustration of the ULSTEIN J102 zero-emission wind turbine installation vessel (WTIV). This vessel can operate 75% of the time in zero-emission mode. Using readily available technology, the additional cost is limited to less than 5% of the total CAPEX.


The X-JACK design driver is to significantly increase the efficiency compared to existing units in the market, both in logistical layout and in payload capacity, while being lighter at the same time. The combination of an innovative hull shape and vessel layout with well-proven jacking and crane technologies from reputable suppliers provides unrivalled heavy lift and cargo capabilities.

The X-JACK concept is scalable and includes three versions: J104, tailored for maintenance and exchange of wind turbines/nacelles; J102, sized for most optimal and cost-effective turbine installation; J103, designed to carry and install six next-generation wind turbines to realize even the world’s most remote wind farm locations.
Read about the ULSTEIN X-JACK initiative.

LNG as a low-emission power source

For Dutch heavy-lift transport specialist Jumbo, ULSTEIN developed the concept and basic design for a new, LNG powered DP2 Heavy Lift crane vessel.

The LNG powered heavy lift crane vessel 'Stella Synergy', an Ulstein design for Jumbo.
The LNG powered heavy lift crane vessel 'Stella Synergy', an Ulstein design for Jumbo.


The 'Stella Synergy' with its two Huisman mast cranes of 2,500 and 400 tonnes, respectively, will be capable to serve both the offshore wind and the offshore oil and gas industry. To minimise the environmental footprint, the vessel features dual-fuel engines, enabling it to operate on LNG.

Subsea Rock Installation newbuild to reach low emission and sustainability goals

Ulstein holds a position as the world-leading ship designer in Subsea Rock Installation (SRI) newbuilds. SRI vessels are important for cable and substructure protection. Our latest design in this field was developed in 2020/2021 and will be the first U.S. flagged and Jones-Act compliant vessel of its kind and the first for the U.S. offshore wind industry. Contracted by Great Lakes Dredge & Dock (GLDD) the vessel will be constructed by Philly Shipyard. The design was reviewed and approved by the American Bureau of Shipping (ABS) and will be built with best-in-class safety and low emissions standards (LEV, Sustain2).


To reach the low emission and sustainability goals, the vessel design includes EPA Tier 4 engines, plug-in shore power connection for loading in ports and battery packs for peak-shaving. The vessel is also able to run on biofuel to reduce its CO2 footprint and is equipped with active emission control technology to minimise NOx emissions.

In the concept phase, the Ulstein Blended Design method was used to enhance cargo efficiency, boost the GLDD business case, and reduce overall fuel consumption.

Ulstein's track record in SRI vessels includes Van Oord’s ‘Bravenes’ vessel and Tideway’s ‘Flintstone’ vessel.

Cable lay operations

The state-of-the-art cable lay vessel ‘Nexans Aurora’ was delivered from Ulstein Verft in 2021.

The CLV vessel Nexans Aurora, the flagship of the Nexans fleet, photo: Per Eide Studio.
The CLV vessel Nexans Aurora, the flagship of the Nexans fleet, photo: Per Eide Studio.


This DP3 vessel plays a vital role in the installation of Nexans’ cutting-edge HV submarine cables that will bring more energy to the world, helping connect offshore wind farms to the grid, supporting electrification of offshore petroleum installations and creating interconnectors between countries.

Ulstein has a long history of designing vessels for harsh conditions and has developed several cable laying designs for the offshore wind market. Ulstein offers CLV designs for all aspects of cable laying operations, including fibre cabling, power cabling and repair.


All the CLV designs in the ULSTEIN SX design series are designed with the patented ULSTEIN X-BOW®. The X-BOW minimises the accelerations, leading to smoother motions and a reduction in fuel consumption in waves. It also diminishes the jerking and wear-and-tear of the cables. The hull is optimised for the vessel’s actual speed range as initial CFD studies can be performed to reduce wave resistance and to verify power requirements.

Service and maintenance vessels

Ulstein was one of the first ship designers to take on the new challenges presented by the offshore renewable energy industry when it designed the “Siem Moxie” (now “Seaway Moxie”). At the time this was the first purpose-built Walk-to-Work vessel, ordered to assist in cable termination and testing during the construction of a wind farm.

Walk-to-Work was soon adopted also for service and maintenance of turbines, leading to the introduction of a new vessel type, the (Construction) Service Operations Vessel, or (C)SOV. When designing its first SOVs Ulstein questioned ship masters how they prefer to operate the vessels at the wind farms. The majority reported that they prefer to manoeuvre stern first for in-field operations, for which they gave various reasons:

All work is being performed from the aft deck. Keeping stern first leads to a better overview of the vessel’s positioning, as the gangway, turbine and ship’s side can all be observed from the operations bridge.

Furthermore, most thrust power is installed in the aft part of the vessel, enabling it to keep positioned more easily and the vessel doesn’t have to turn around before moving to the next turbine, saving manoeuvring time between turbines.

Ulstein already had great feedback from its patented X-BOW hull shape, which significantly reduces slamming and vibrations caused by waves in head seas. For vessels operating astern regularly, such as these vessels servicing the offshore wind farms, Ulstein introduced the X-STERN in 2015. This was awarded the Next Generation Ship Award by Nor-Shipping, recognising the most promising design among the ships that will be at sea in the coming decade, demonstrating the biggest advances and innovation in design. The design is assessed with respect to energy efficiency, innovation, suitability and flexibility, utilisation of technology, safety and security and environmental sustainability.

Five new build projects with the X-STERN have now been delivered from Ulstein Verft, and several more are planned for construction internationally.

The crews on X-STERN vessels report additional benefits

The X-STERN is kept towards the weather while on standby during the night. The service crews get complete rest in between their maintenance shifts due to no slamming or vibrations.

There is no slamming due to the X-STERN even when transferring between turbines.

    If the weather is not too adverse, the ship stays on the spot with only two thrusters running, which leads to a substantial reduction in fuel consumption during stand-by.

    The X-STERN hull also provides major fuel savings. Findings show that the X-STERN results in up to 60 per cent less power required when manoeuvring stern first compared to a flat transom stern.

    Also, read the story of the senior DP operator on the first X-STERN Service Operation Vessel.

      Next-generation service vessels

      Ulstein Group has a clear ambition of being at the forefront of the technology development required to achieve zero-emission offshore operations. One important design aspect in achieving this goal is our innovative hulls, including our novel TWIN X-STERN. These ships leverage the advantages of the X-STERN by creating an underwater hull shape that is bi-symmetrical with two main propeller units in each end, ideal for offshore operations requiring continuous positioning. The TWIN X-STERN is more manoeuvrable, with low noise for more comfort onboard and the potential to save significant amounts of energy.

      By having excellent performance in any direction, and more efficient utilisation of the thrusters, high performance is achieved with the minimum required power. The result is significantly more effective operations and reduced energy consumption, which is the key to performing vessel operations with reduced emissions

      To lower the vessel’s environmental impact further, moving towards zero-emission, Ulstein is preparing future-proof power solutions. Ulstein’s SOVs and CSOVs can be delivered as diesel-electric battery hybrids as a starting point, with options for further emission reduction installed or prepared for. Being technology and supplier neutral, Ulstein can guide the client to the most suitable fuel and power conversion technology for their business case, taking into account project-specific requirements, supply chain considerations and the operational profile of the vessel.

      The vessel designs and solutions mentioned here are examples of what Ulstein can do for you in offshore wind.

      We are innovators – challenge us!

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