| Written by Mark Buzinkay
Table of contents:
- A first walk through a wind farm vessel
- The hull and protection of a wind farm vessel
- What type of engines do you find on wind farm vessels?
- What is dynamic positioning?
- FAQs
- Takeaway
- Glossary
A first walk through a wind farm vessel
An SOV is not just a vessel. It is a working and living platform for a crew of 50 to 100 personnel for two or more weeks, designed for specific tasks in the offshore energy industry. That's why an SOV is so big and complex. Let's get on board and have a detailed look at what's inside.
A vessel is always described and divided into decks, which are levels in a building. Some decks are below the waterline, and some are above the waterline.
The decks under the waterline accommodate the pump room (at the bottom of the vessel), the engine room, the auxiliary machinery room, diverse fuel storage tanks, the thruster room(s), and the propulsion room.
One deck higher and at the waterline, you'll find the electric room, the transformer room, diverse control rooms, and sometimes the Hotel auxiliary room, as shown in our illustration of the ICE WS-60-SOV.
The main deck on an SOV gives you the warehouse, changing area, workshop and diverse temporary storage, sometimes with space for several standard 20ft containers. This location is easily accessible from both the exterior work areas, where the maintenance of offshore wind turbines and other equipment takes place, and the internal storage compartments, which house spare parts and tools. Depending on the ship's design, the main deck can serve as the main working deck for handling equipment and supplies necessary for wind farm maintenance.
In our illustration, the main working deck aft the vessel is on a higher deck (Deck A). Also, it harbours a lifeboat, a daughter craft, a 3D motion-compensated crane, a provision crane, and a 3D motion-compensated gangway. Cranes and other lifting equipment facilitate the loading and unloading of heavy components.
The cabins on the main, A, and B decks are located in the mid-ship and front sections of the vessel. This placement gives easy access to both the main deck's operational areas and the bridge at the top of this area. This setup also improves comfort (daylight) and safety by providing quick access to life-saving equipment and muster points.
The galley, lounges, offices, meeting rooms, and gym are in the B, C and D decks. The emergency room (mid-ship, B deck) also offers a weather deck on top of it, which can also be used as additional container storage space. The helideck is above the stern on deck level D, ideally seen from the bridge (Bridge deck), the highest deck on an SOV, providing a panoramic view of the surroundings. This area is equipped with advanced navigation and communication systems, enabling the crew to monitor and control the vessel's movements accurately.
The hull and protection of a wind farm vessel
To begin with, why an offshore wind farm service vessel is designed the specific way, we need to understand how the waters and climate of the North Sea influence the SOV. Wave patterns, strong currents, and significant tidal ranges. What is the most important thing to consider when creating those floating pieces of the latest technologies to ensure safety, efficiency, stability, and durability under any conditions?
Since the North Sea has relatively shallow waters, especially compared to other seas and oceans, it can often be choppy and high waves often occur during storms. It affects mostly smaller vessels, but it can easily be felt on SOVs. Also, not often, but it might still happen, during harsh winters, Arctic ice can drift into the North Sea, mostly because of the East Greenland Current.
For the stability and to ensure low resistance of the vessel, when designing the hull model, testing and computational fluid dynamics tools (CFD) are used.
SOVs are mostly built from a material called marine-grade aluminium. Pure aluminium resists corrosion well, but in marine environments, since it's constantly exposed to water and moisture, it needs extra protection. When it is mixed with different metals i.e. magnesium, it becomes even more resistant to corrosion, making it suitable for constant contact with water and saltwater. Another aspect is the weight. The construction is much lighter when built using aluminium than iron or steel. It's also easier to shape, saving big costs on the labour and material side.
With all of this taken into consideration, the hull design is a compromise between the safety, efficiency and productivity of the vessel, from the shipyard to the end of its journey. The shapes of them started to evolve. One of the first designs which influenced the market of offshore vessels was X-BOW, introduced in 2005. Created by Ulstein, this inverted bow concept revolutionised the shipbuilding industry. The design significantly enhanced fuel efficiency through improved hydrodynamics. The unique shape reduced the wave impacts, leading to gentler wave entries. This structure also decreased noise and vibration, contributing to a quiet onboard environment. It helped to maintain consistent speeds by mitigating speed loss in challenging sea conditions and reducing spray significantly, which kept the deck drier and safer.
Building a vessel to prevent corrosion is one thing; there are many different ways to protect the hull from being destroyed. In the early days of sailing, before engines were developed, to coat vessels' hulls, people used lime and later arsenic, which, as you can imagine, were bad for the environment. Nowadays, the chemical industry has developed effective anti-fouling paints which use metallic compounds. Thanks to it, sealife, such as algae and molluscs, cannot attach themselves to the hull, which slows down vessels and increases fuel consumption.
What type of engines do you find on wind farm vessels?
Luckily, today's reality is not about sails and paddles but engines propelling and creating power on board. An SOV like the Windea Leibniz, weighing 3150 tonnes, 88m in length, and a maximum speed of 13.5 kn, needs powerful engines to perform reliably and precisely even in challenging sea conditions.
However, power generation enables propulsion and covers all other electrical power needs on board: Electronic instruments, motion-compensated gangways, cranes, lightning, tools, and accommodation.
An SOV typically features a main engine, auxiliary or backup engines, and power storage systems. Earlier SOVs relied on highly efficient marine diesel or marine gas oil engines, but today's choice is a hybrid combination of diesel and electric motors, with diesel engines acting as backup.
Typically, diesel engines produce around 1,500–4,000 kW per engine, and the total installed power on an SOV often exceeds 10,000 kW. For environmental reasons, these installations include selective catalytic reduction systems for NOx and particulate filters for their exhaust. Low-sulfur fuel (LFO) and alternatives such as LNG are standard, but methanol is growing in popularity. Dual-fuel engines are already available on the market and enable operations with different fuel types.
Engines can be used in different ways—in propulsion mode or to create electrical power. Let's examine the differences through the example of an industry-popular engine: the MAN 175D propulsion engine and the MAN 175D GenSet, respectively.
Some companies are already prepared for "true zero emission" operations. The Royal IHC SOVs, powered by hybrid and full battery-power propulsion systems, are designed to achieve the lowest emissions during operation at the wind farm by using hydrogen or other alternative fuels.
Electrical motors typically have a power output of 500 kW to 3,000 kW per motor and run at high voltages, normally between 690V and 11kV. This allows them to transmit adequate power with low losses. Their 'fuel' is electric power supplied by batteries or directly generated by onboard GenSets. Battery storage can be refuelled by a variety of onboard energy sources, including renewable energy (e.g. solar) and the onshore and offshore electrical grid (wind turbine or supply vessels).
Propulsion Systems
A marine propulsion system is the technology used to move watercraft on the water. These systems operate based on Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. This means that the force applied by the propulsion system to the water generates an equal force that moves the vessel forward.
Diesel engines are the most commonly used type of propulsion system today in the maritime world. They are used as main as well as auxiliary engines and work far more efficiently than previous solutions, which in this case was a steam engine. The second most popular solution is a diesel-electric propulsion system; a diesel engine powers electric generators that power the propeller motors. Multiple diesel engines generate and supply electricity to the propulsion components. These components typically work on the principle of speed-controlled AC motors and drive the propeller either directly or through reduction gears.
Diesel-electric propulsion systems are used in a wide range of vessels. Their applications include mega yachts, research vessels, offshore vessels, heavy-lift jack-up vessels, passenger ferries, cable-laying vessels and cruise liners.
Advanced engines and propulsion systems are developed and produced at the core by leading manufacturers. MAN and Rolls-Royce Marine offer integrated power and propulsion, including diesel-electric and hybrid systems. Rolls-Royce's Bergen B33:45 series of engines are extremely efficient and environmentally friendly, coupling high performance with low emissions. Wärtsilä is also among the major integrators and suppliers of marine engines and hybrid solutions. This, in turn, includes the Wärtsilä 31 engine, which holds the Guinness World Record for the most efficient 4-stroke diesel engine.
What is Dynamic Positioning?
Conventional vessels combine engines, propulsion and propellers to move forward and backwards. However, extremely high precision in manoeuvrability or Dynamic Positioning is crucial for operating SOV within a wind park. Keeping a vessel at a fixed position and heading is necessary for multiple offshore operations. Back in the day, this was done using an anchor spread. Now, Dynamic Positioning (DP) has fully replaced anchors with the help of thrusters. The DP system controls the position and heading of a vessel by using thrusters that are constantly active and automatically balance the environmental forces such as current, waves and wind. Those forces are trying to move the vessel off the desired position when the automatically controlled thrust balances environmental forces and keeps the vessel in the position it should be.
Azimuth thrusters, which can rotate to direct thrust in any direction for precise manoeuvring, are best suited for dynamic positioning. Tunnel thrusters, located at the bow or stern, provide lateral thrust to help with docking and maintaining position. Retractable thrusters can be lowered into the water when needed and retracted when not in use, offering the advantages of both azimuth and tunnel thrusters.
The DP system comprises a control system which calculates the difference between the actual and desired position. Based on them, the control system determines the required forces the thrusters must apply to correct errors.
The power generation provides the energy required for the system to function, such as the power management system (PMS) for monitoring and controlling power generation and distribution, and the thruster allocation logic (TAL) for calculating and distributing thruster commands from the DP controller to individual thrusters. The power and thruster monitoring process involves observing and analysing the power and thruster status, performance, and behaviour during the DP operation. It is important to monitor a range of power and thruster parameters, such as power consumption, generation, and balance, which indicate the efficiency and stability of the power system. Finally, it's the environmental reference, which monitors conditions to help the system make accurate adjustments and the position and heading reference, which provides the data needed for the control system to keep the vessel stable.
There are three classes of Dynamic Positioning, which are linked to redundancy levels:
- Class 1 involves automatic and manual control of position and heading without redundancy, meaning a single fault can result in a loss of position.
- Class 2 also features automatic and manual control of position and heading, but it is designed to prevent loss of position from a single fault in active components like generators or thrusters. However, loss of position can still occur if static components such as cables or pipes fail.
- Class 3 provides automatic and manual control of position and heading with full redundancy and separation of components. It is designed to prevent loss of position from any single failure, including major incidents like a fire or flooding in watertight compartments. Most of the new-era SOVs have DP 2 standards.
Want to learn more about other SOVs? Wait for our next blog post or get our SOV book for free.
FAQ: Wind Farm Vessel Design and Propulsion
Why are wind farm vessels, especially SOVs, so large and complex?
Service Operation Vessels must accommodate 50–100 crew members (see also: e-POB) for weeks at sea while supporting offshore wind farm maintenance. Their size allows space for workshops, storage, cabins, control rooms, and safety systems, ensuring both operational efficiency and crew comfort.
What role does the hull design play in safety and efficiency?
The hull is optimised using computational fluid dynamics to withstand North Sea conditions. Designs like the Ulstein X-BOW reduce wave impact, improve fuel efficiency, and enhance onboard comfort by minimising noise, vibration, and spray.
What propulsion systems are used on wind farm vessels?
Modern SOVs use hybrid diesel-electric propulsion with advanced thrusters for dynamic positioning. This allows precise manoeuvring within wind farms and ensures redundancy for safety. Dual-fuel and battery-supported systems are increasingly common, reducing emissions and enabling future zero-emission operations.
Takeaway
The success of a wind farm vessel lies in balancing safe operations with the comfort and efficiency of personnel on board. With up to 100 crew members living and working at sea for weeks, every design choice—from cabin layout to emergency access—supports safety and well-being. Critical to daily operations is the walk-to-work gangway, which ensures secure and reliable transfer between vessel and turbine. Together with advanced positioning systems and robust onboard facilities, these features make SOVs indispensable in maintaining safety and productivity in offshore wind energy.
Delve deeper into one of our core topics: Personnel on board
Glossary
A thruster in naval engineering is a propulsion device used to manoeuvre vessels with high precision, especially in confined or offshore environments. Unlike main propellers, thrusters can provide lateral or multidirectional thrust, enabling docking, station-keeping, or dynamic positioning without forward motion. Common types include tunnel, azimuth, and retractable thrusters, each suited to specific operational needs. Their integration with dynamic positioning systems makes them vital for modern offshore vessels. (2)
References
(1) M. Buzinkay & M. Wozniakowski-Zehenter (2025): The Journey. Life and Work on a SOV.
(2) Carlton, J. (2018). Marine Propellers and Propulsion (4th ed.). Butterworth-Heinemann.
Note: This article was partly created with the assistance of artificial intelligence to support drafting. The head image was generated by AI.
