From oil and gas to offshore wind

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For generations, we have delivered ship designs to service oil and gas installations in the world’s harshest sea areas. Offshore wind is a new segment in the offshore family, and the knowledge of how the weather can impact the vessel is of great value when developing designs and solutions for offshore renewables.

Service and assistance vessels

The ‘Windea La Cour’ was among the first of the new breed of service and operation vessels (SOVs) entering the market. Awarded the 'Offshore Renewables Award' in 2017, the 88 metre-long vessel of the ULSTEIN SX175 design is operated by Bernhard Schulte Offshore and contracted by Siemens Wind Power. She commenced work on the large, 150-turbine Gemini wind farm 85 kilometres offshore the Netherlands in September 2016. Performing wind farm operations, the vessel’s main task is to transport and accommodate service technicians, and to transfer them safely over to the wind farm installations. Her sister vessel, the 'Windea Leibniz', is servicing Vattenfall's offshore wind farms Sandbank and DanTysk in the German Bight.

Construction support
Two vessels of a larger design, the ULSTEIN SX195, were later contracted by Acta Marine, of which the first, the 'Acta Auriga', was delivered in 2018. The vessel is operating as an SOV for Ocean Breeze on their BARD Offshore 1 offshore wind farm, and can also work as a construction support vessel (CSV). A part of the requirement was to have the crane and gangway in the centre of the vessel, to increase operational flexibility. The vessel has a motion compensated gangway system with a lift, and a 3D, fully motion compensated, cargo crane capable of lifting 6 tonnes. Here's why the 'Acta Auriga' was chosen for BARD Offshore 1.

The first X-STERN vessel caused attention
The X-STERN is one of Ulstein’s many innovative contributions to the offshore wind segment. Placing the stern to weather reduces pitch motion and substantially lowers the required power in station keeping compared to bow into the weather. An intriguing side effect is the ability to keep high backwards speed. 'Windea La Cour', being the first vessel with an X-STERN, raised attention whilst on sea trials due to her high backwards speed of 12.1 knots, close to the forward speed of 13.95 knots, watch film. The vessel is very flexible when moving around in the wind farm, and it does not matter where the weather is coming from or where she is heading next. The vessel is also carrying the X-BOW, a similar design for the bow. By lowering the acceleration levels of the bow and stern, the design minimises slamming impact.

Matthias Giebichenstein, senior DPO on the Windea La Cour.

Matthias Giebichenstein, senior DPO on the Windea La Cour. Read his story: Hard rocker at work, enjoying the silence.

The bow and stern designs improve the sea-keeping abilities and eliminate abrupt stops from head seas. The vessels can easily go either way, and their nimbleness and flexibility make them ideal for working close to the offshore wind farm installations.

First dedicated SOV delivered in 2014
The first dedicated SOV/ISV vessel developed by Ulstein, the ‘Siem Moxie’ (now: Seaway Moxie), delivered 2014 from Fjellstrand, also sported several new features, including Voith Schneider propulsion and a new type of crane and capability for installation support. Operated by Seaway Offshore Cables, she has been working as an installation support vessel together with the cable lay vessel ‘Siem Aimery’, now: 'Seaway Aimery.' The pair have set new standards in offshore wind submarine cable installation. The duo has been specifically designed and built to serve the demanding needs for safe and reliable offshore operations in rough seas. 'Seaway Moxie' transports work crews to the platforms and foundations to prepare for submarine cable pull-in and terminations.

The 'Siem Moxie', first dedicated SOV, operating in a Siem duo as an installation support vessel.

The 'Siem Moxie' (now: 'Seaway Moxie'), first dedicated SOV, operating in duo with a cable laying vessel as an installation support vessel.


Equipped with an active heave compensated gangway, the 'Siem Moxie' ('Seaway Moxie') reported more than 14,000 individual connections to offshore structures, transferring in excess of 54,000 personnel from start-up in April 2014 till November 2017, proving her capability as one the most advanced, safe and efficient service operations vessels available in the market.

Installation work

Offshore wind farms are being established further from shore, and more offshore wind farm work could be carried out by monohull vessels, including foundation installation.

Heavy lift crane operations
Ulstein has developed the concept and basic designs for an LNG powered DP2 Heavy Lift crane vessel for the Dutch transportation and installation contractor Jumbo, an expert in the installation of fixed facilities such as wind turbine foundations.


The 'Stella Synergy' will be the largest X-BOW® vessel to date and with its two Huisman mast cranes of 2,200 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 to operate on LNG.

The jack-up concept SOUL
One of the design areas at Ulstein specialises in offshore heavy-lift. Given the trend in the industry for even bigger wind turbines, larger installation units will be required or different installation methodologies.

Ulstein, in cooperation with SeaOwls, has introduced the jack-up concept, SOUL, which aims to serve the future needs of the offshore wind industry. SOUL is scalable and suitable for various crane sizes, variable loads and deck lay-outs. The design driver is to significantly increase the efficiency compared to existing units in the market, both in logistical lay-out as in pay load capacity. The jacking technology is considered the most critical element for a jack-up and for SOUL, Ulstein will make use of existing and proven jacking systems.

For installation work, especially for the foundations, the most effective tool is a floating platform. It makes installation faster as it is less restricted by jacking operations. Then, it makes sense to install the nacelle and turbine blades from a jack-up, as it has more precision high up.

Cable laying operations
The LX109 cable lay shipdesign is a high-capacity cable lay vessel with compact dimensions, dedicated for export power cables for the offshore wind industry. Implemented in open top vessel design is the patent-pending ULSTEIN Cable Arch system, which results in a total of 12,500 t of power cable that can be laid as one single piece.

Rock installation services
Ulstein also provides the engineering services and hardware solutions for vertical and inclined fall-pipe systems for subsea rock installation. One such vessel is Van Oord's ‘Bravenes’ subsea rock installation vessel, which commenced its first assignment in the North Sea offshore Norway in 2018. Watch animation about the 'Bravenes' functionalities.

This vessel is suitable for installation of a wide range of rock sizes through a fall pipe at the side of the vessel. With a deadweight of 14,000t, a length of 154 metres and a beam of 28 metres, the vessel can operate in water depths of more than 600 metres.

Windlifter turbine installation
The Windlifter™ is a system which is designed to transport and (de-)install completely pre-assembled offshore wind turbines – complete with nacelles and blades - in single-lift installation for bottom fixed foundations. The system comprises a storage and handling system for multiple turbines for efficient transport, which is linked to a mechanical system to skid the turbines safely and fully controlled from the vessel onto the foundation. The concept has been designed as a modular system to allow flexible utilisation of available vessels.

In 2015, a customized version was accepted as one of the winner’s in the Statoil (from 2018: Equinor) innovation campaign, the Hywind Installation Challenge. In the Statoil campaign, it was adopted to work with the floating Hywind foundation.

3D motion-compensated crane handling

The next natural step in increased operability will be motion-compensation. Awarded the IRO Innovation Award, the TTS COLIBRI™ crane add-on is a compact and efficient 3D motion-compensated handling system to increase vessel operability, enabling smaller and more cost-effective vessels to be used in harsher weather conditions. The system is very flexible, as it can be mounted on the tip of a crane as a new-build option, or as a retrofit. A TTS Colibri crane has been contracted to a newbuild offshore wind SOV project for Louis Dreyfus Armateurs with planned delivery in 2018.