The number of offshore wind farms put into service has rapidly increased recently. The new installations take advantage of stronger and more consistent wind patterns found at sea compared to onshore locations, leading to higher efficiency, output, and, therefore, profits. The size of the offshore wind farm is bigger, avoiding space limitations and land use impacts of onshore projects.
The offshore wind farm construction and running cycle is a complicated process that requires careful planning. In this process, wind farm support vessels provide the requisite logistical support for the installation, running, and servicing of the turbines and other ancillary infrastructure. These vessels are specially designed to face challenging marine conditions and perform a host of tasks that become imperative for the farms' success.
The vessels involved in offshore wind farm development have unique roles and competencies. These include installation vessels, service operation vessels, crew transfer vessels, cable-laying vessels, and multipurpose support vessels. Understanding the functions and features of each type is crucial to appreciating their importance in the offshore wind energy sector.
Wind Turbine Installation Vessels (WTIVs)
Wind turbine installation vessels are at the very leading edge regarding size and specialisation within the fleet. They have heavy-lift cranes, dynamic positioning systems, and large deck areas for transporting and installing massive components like wind turbine foundation structures, towers, nacelles, and rotor blades. These vessels are designed to handle the weight and size of the turbine components and to operate in deep water and rough sea conditions.
Installation starts with transporting the turbine components from the manufacturing site to an offshore location. Installation vessels position the foundations on the seabed, often using advanced anchoring or jacking systems to secure them. After fixing the foundations, towers and nacelles are erected, and blades are assembled. This requires very precise manoeuvring and coordination; even a small mistake may create a huge delay and, hence, increased costs.
Service Operation Vessels (SOVs)
Service operation vessels (SOVs) form an integral part of the continuous operation and maintenance underway for any offshore wind farm. They are designed to stay at sea for periods while providing accommodation to technicians and support in maintaining the turbines. SOVs are equipped with advanced dynamic positioning systems to maintain a position next to the turbines to safely and efficiently transfer personnel and equipment.
These SOVs act as a mobile operating base with workshops, storerooms, and accommodations. They allow teams of maintenance personnel to carry out planned inspections, repair, and upgrade the turbines to keep them running efficiently and at optimum capacity. SOVs' ability to function in rough seas and stay on station for extended periods has made them especially useful in ensuring the reliability and efficiency of an offshore wind farm (see also: Walk-to-work offshore).
Crew Transfer Vessels (CTVs)
Crew transfer vessels (CTVs) play a vital role in the daily operations of offshore wind farms. These smaller, high-speed vessels are designed to transport technicians and small cargo from shore to the wind farm and between turbines. CTVs are equipped with specialised gangways or boat landing systems to facilitate the safe and efficient transfer of personnel in various sea conditions.
The design of CTVs emphasises speed, stability, and safety. They are typically catamaran or SWATH (Small Waterplane Area Twin Hull) vessels, providing a stable platform for personnel transfers even in moderate sea states. The ability to quickly and safely transfer technicians to the turbines is crucial for timely maintenance and emergency response, ensuring the continuous operation of the wind farm (see also: the fast crew boat).
Cable-Laying Vessels
Cable-laying vessels are specialised ships used to install the submarine power cables that connect the wind turbines to each other and to the onshore grid. These vessels are equipped with large cable drums, sophisticated cable handling systems, and precise positioning technology to ensure accurate placement of the cables on the seabed.
The cable-laying process involves several stages, starting with surveying the seabed to plan the optimal cable route. The cables are then laid using specialised equipment that minimises tension and prevents damage. Cable-laying vessels are capable of burying the cables to protect them from damage by fishing gear, anchors, and marine traffic. The accurate installation of these cables is crucial for efficiently transmitting electricity generated by the wind turbines to the grid.
During different phases of the development of an offshore wind farm, different kinds of support vessels are required. The phases are site investigation, construction, operation, and decommissioning. In all these phases, the role played by wind farm support vessels concerning the successful completion and running of a wind farm is quite significant.
Site investigation is the very first stage of the development of an offshore wind farm, including environmental assessments, seabed surveys, and meteorological studies. In this regard, support vessels are critically involved in conducting geotechnical and geophysical surveys over the seabed to determine its condition and, hence, find areas suitable for setting up a turbine.
This means that the seabed would have to be mapped using survey vessels fitted with sonar and magnetometers, along with sampling equipment, to identify hazards and obtain data on the composition and stability of soils. Data of this kind is very critical in designing the foundations and planning the installation process. Accurate site investigation ensures the safe and efficient construction of the wind farm by minimising the risks of facing unexpected challenges during the installation phase.
This is naturally the most intensive stage in construction, which would call for another diverse fleet of vessels to transport and install wind turbines and associated equipment. Installation vessels transport and erect turbine parts; laying submarine power cables by dedicated laying vessels; SOVs and CTVs provide logistical support by transporting technicians and equipment around the place of construction.
The installation of the turbines requires exact coordination and timing during construction. The installation vessels have to work in close proximity to other vessels and to the turbines, so they require advanced dynamic positioning systems to hold their position. The ability of support vessels to perform tasks in poor marine conditions is of great value in completing a wind farm on time.
Once operational, the wind farm still needs support vessels to maintain and operate it. SOVs provide accommodation and a working platform for maintenance teams so that routine inspections, repairs, and upgrades on the turbines can be carried out. Equally, CTVs enable personnel transfers on a daily basis, where technicians are able to reach the turbines not only quickly but also safely.
Effective functioning of the wind farm is impossible without regular maintenance. Maintenance identifies problems before they become critical failures. SOVs and CTVs provide an opportunity for maintenance personnel to access turbines at any time during a range of sea states, thus ensuring that maintenance tasks can be done at all times. Therefore, this potential to work effectively in rough conditions is fairly important to wind farm reliability.
This is the stage at which the wind turbines and associated infrastructure are removed at the end of the farm's operational life. Support vessels were used to dismantle and transport turbine components, cables, and foundations to the shore for recycling or refuse. Such a process needs careful planning and coordination for safe and environmentally responsible decommissioning.
Such vessels require heavy-lift cranes and specialised equipment to handle large, heavy turbine components. The execution is carried out with the same level of care and precision as the installation phase, ensuring the safe removal of the turbines and infrastructure without harming the marine environment.
The development and operation of offshore wind farms have thus far driven significant technological achievements regarding support vessels. These improvements increase the efficiency, safety, and environmental sustainability of vessel operations, thus contributing to the overall success of wind farms.
Dynamic positioning systems (DPS) are used for accurate manoeuvring and positioning of support vessels. DPS keeps the vessel's heading and position in the right alignments using a mix of global positioning, sensors, and thrusters against difficult sea conditions. In installation vessels, service operation vessels, and cable-laying vessels, DP systems are indispensable because they can operate close to the turbines and other infrastructure.
Advanced DPS ensures vessel safety and efficiency, reducing the risk of collisions and offering precise positioning for operations of high sensitivity. Some of the critical features include the ability to hold a stable position in rough seas for personnel transfer and heavy-lift operations.
ROVs are unmanned, self-contained submersible vehicles equipped with cameras, sensors, and manipulation tools. They perform underwater inspection, maintenance, and construction-related missions. ROVs enable support vessels to conduct close, detailed inspections of turbine foundations, cables, and other submerged infrastructure without divers.
ROVs improve safety and efficiency for underwater operations, including high-quality inspections and repairs under difficult conditions. ROVs can easily reach their destination where deployment by a diver is either impossible or incurs risk; this will provide invaluable data to enable proactive maintenance of infrastructure at the wind farm.
Windfarm support vessels in the recent past have made vital considerations about the environment while in design and operation. Hybrid and electric drive systems, contrary to the already existing problem of emission reduction and fuel efficiency, are being gradually adopted. These systems combine traditional diesel engines with electric motors and battery storage, allowing vessels to carry out their duties effectively and environmentally friendly. Shane Guidry, CEO of Harvey Gulf said in the interview for the Offshore Engineer: "Today, LNG, renewable LNG (RLNG) and battery power is the answer to lowering our carbon footprint. Tomorrow, maybe the question isn't why or why not, but when will the customer be willing to pay more for vessels with all these carbon reduction assets, as they still don't today? And when will the government offer tax credits for companies using these carbon reduction technologies? Until then, companies just won't commit the capital."
Such hybrid and electric drive trains deliver numerous advantages in reduced fuel consumption, lower emissions, and quieter operations. In an offshore wind farm context, all these benefits assume more significance since environmental impact has to be kept at the lowest possible level. The assimilation of green technologies in support vessels furthers the general goals of renewable energy and sustainability.
Modern support vessels are equipped with advanced and sophisticated communication and navigation systems to maximise operational efficiency and safety. These include state-of-the-art satellite communications, radar, AIS, and integrated bridge systems, to mention a few. Improved connectivity options and better navigation allow for monitoring and coordination of vessel operations in real-time, enhancing situational awareness and decision-making.
Advanced communication systems allow problems to be easily relayed to support vessels, shore operations centres, or other relevant parties. This kind of connectivity is critical to managing the complex logistics associated with offshore wind farm operations and ensures that any issue or emergency encountered is dealt with in good time.
The operation has environmental implications, and the industry is committed to minimising its impact on the marine ecosystem. Efforts to enhance the sustainability of support vessels include adopting cleaner technologies, implementing best practices for environmental management, and ensuring compliance with regulations.
One of the primary environmental goals is to reduce greenhouse gas emissions. The adoption of hybrid and electric propulsion systems, as well as the use of low-sulfur fuels, contributes to this goal. Additionally, optimising vessel operations, such as reducing transit speeds and improving route planning, helps to minimise fuel consumption and emissions.
Underwater noise from vessel operations can impact marine life, particularly cetaceans and other sensitive species. Efforts to reduce noise include using quieter propulsion systems, implementing noise-reducing technologies, and adopting operational practices that minimise noise generation. Monitoring and mitigating underwater noise are important for protecting the marine environment.
Proper waste management is essential for minimising the environmental impact. Vessels have waste handling systems to manage and dispose of waste responsibly. This includes segregating and recycling waste, treating sewage and bilge water, and ensuring no harmful substances are discharged into the marine environment.
The construction and operation of offshore wind farms, must consider the protection of marine biodiversity. This involves conducting environmental impact assessments, implementing mitigation measures to avoid or minimise habitat disturbance, and monitoring the impact of operations on marine species. Protecting biodiversity is integral to the sustainable development of offshore wind energy.
What are Windfarm Support Vessels?
Windfarm Support Vessels are specialised ships designed to assist in the construction, maintenance, and operation of offshore wind farms. These vessels are equipped with advanced technologies to tackle the unique challenges of working at sea. There are several types of WSVs, each serving specific purposes.
Crew Transfer Vessels (CTVs) are high-speed, stable platforms that transport crew and technicians to and from offshore wind turbines, ensuring safe and efficient transfers. Service Operation Vessels (SOVs) provide accommodation and logistical support for long-term maintenance operations. They are equipped with Dynamic Positioning (DP) systems, motion-compensated gangways for safe transfers, and facilities for housing crew and technicians. Construction vessels support the installation of wind turbines and related infrastructure, boasting heavy lifting capabilities and large deck space for equipment and materials. Cable-laying vessels specialise in installing and maintaining submarine power cables that connect wind turbines to the grid, utilising specialised cable handling and precise navigation systems. Heavy lift vessels transport and install large wind turbine components, such as foundations, towers, and nacelles, with their massive cranes and stability systems.
Windfarm support vessels have contributed to the overall success of offshore wind farms, from construction through operation and maintenance to eventual decommissioning. Specialised vessels ensure that renewable energy generation is both efficient and reliable by incorporating advanced technologies and innovative design features for sea-based operations in harsh marine environments. In a sense, innovation within wind farm support vessels mirrors the ever-changing nature of the offshore wind industry as it drives efforts toward sustainability, efficiency, and safety.
Windfarm support vessels have huge implications economically, socially, and environmentally. The industry provides job creation, economic activity, and energy security while remaining top of the agenda for environmental sustainability and biodiversity protection. As the wind offshore industry grows and evolves in its nature, so will the leading position of windfarm support vessels within the low-carbon future and global effort against climate change.
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Sources:
(1) https://www.oedigital.com/news/495715-interview-shane-guidry-harvey-gulf
(2) https://www.renewableenergymagazine.com/interviews/the-future-of-offshore-wind-support--20160727