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Windfarm construction is among the most demanding engineering and logistics operations in the renewable energy sector. Unlike onshore projects, offshore wind farms must be built in remote marine environments where weather conditions, sea state, and limited installation windows significantly influence construction schedules.
Modern offshore wind turbines are massive industrial structures. Turbine towers can reach heights of more than 150 meters, while blades alone may exceed 100 meters in length. Individual turbine components can weigh several hundred tonnes. Transporting and installing these elements offshore requires a carefully coordinated sequence of maritime logistics operations, specialised vessels, and highly trained crews.
The process typically begins long before installation vessels arrive offshore. Foundations, towers, nacelles, and blades are manufactured in different facilities and transported to staging ports, often called marshalling ports. These ports serve as assembly and storage hubs where components are prepared for transport to the windfarm site.Once construction begins offshore, multiple installation phases take place. Foundations such as monopiles or jacket structures are installed first. These foundations must be precisely positioned on the seabed and secured using specialised piling equipment or other installation techniques, depending on water depth and seabed conditions.
After the foundations are in place, installation vessels begin assembling the turbines. Towers are lifted and mounted onto foundations, followed by the nacelle and finally the blades. Each step requires precision lifting operations using cranes capable of handling extremely heavy loads while operating in offshore conditions.
Weather conditions play a major role in wind farm construction. Strong winds, high waves, and poor visibility can delay installation operations, so project developers must carefully plan schedules around available weather windows. Because offshore installation vessels are expensive to operate, even small delays can have significant financial impacts.In addition to turbine installation, windfarm construction also includes the installation of inter-array cables and export cables. These subsea cables connect turbines within the wind farm and transmit electricity back to shore. Cable installation requires specialised vessels and careful seabed preparation to ensure long-term reliability.
Overall, windfarm construction involves coordinating numerous stakeholders, including vessel operators, engineers, logistics planners, port authorities, and offshore technicians. Managing this complex ecosystem efficiently is essential for ensuring that projects remain on schedule and within budget.
Traditional windfarm construction follows a relatively standardised installation model that has been used in the offshore wind industry for many years. This model relies heavily on large installation vessels that transport turbine components from port to the offshore site and perform the installation operations themselves.
The process typically begins at the marshalling port, where turbine components are delivered from manufacturing facilities. Towers, blades, and nacelles are staged and prepared for offshore transport. Installation vessels then load several complete turbine sets onto their decks before sailing to the windfarm site.
Once at the site, the vessel positions itself next to a prepared foundation. Most installation vessels are jack-up vessels, which means they can lower legs to the seabed and elevate the vessel above the water surface. This creates a stable platform for heavy lifting operations.
From this elevated platform, large cranes lift the turbine tower sections into position and secure them to the foundation. Next, the nacelle is installed at the top of the tower. Finally, the blades are mounted either individually or as a preassembled rotor.
After installing one turbine, the vessel retracts its legs, moves to the next foundation location, and repeats the process. This sequence continues until all turbines have been installed.While this approach has enabled rapid offshore wind growth over the past two decades, it also presents several operational challenges.
One of the main limitations of traditional windfarm construction is the heavy reliance on installation vessels for both transport and installation tasks. These vessels are extremely expensive to operate, with daily charter rates that can reach hundreds of thousands of euros. When these vessels spend time sailing between ports and the offshore site, they are not performing installation work, which reduces overall efficiency.
Weather conditions can further complicate this process. If weather conditions deteriorate while the vessel is travelling or preparing for installation, operations may be delayed for extended periods. Because the installation vessel is central to the entire operation, delays can quickly propagate through the project schedule.
Port infrastructure also plays an important role. As turbine sizes increase, ports must provide larger storage areas, deeper berths, and stronger quaysides to handle heavy components and installation vessels. Limited port capacity can create bottlenecks that slow down project timelines.
These challenges have encouraged developers and engineering companies to explore new approaches to windfarm construction that improve logistics efficiency and reduce reliance on a single vessel performing multiple roles.
As offshore wind farms grow larger and turbine sizes continue to increase, the industry is searching for ways to improve installation efficiency and reduce construction costs. One promising approach is the feeder-based installation model, which separates transport and installation tasks. In a feeder-based windfarm construction approach, the main installation vessel remains at the offshore site throughout the installation campaign. Instead of returning to port to collect new turbine components, specialised feeder vessels transport components from the marshalling port to the installation vessel offshore.
This model allows installation vessels to focus exclusively on turbine assembly, maximising their productivity during favourable weather conditions. One company actively promoting this approach is ONP Management, based in Germany, which has developed the Feederdock concept. The Feederdock system is designed to optimise the logistics chain between ports and offshore installation sites.
Under this concept, feeder vessels load turbine components at the marshalling port and transport them to the installation vessel waiting offshore. Using specialised transfer techniques, the components are then transferred from the feeder vessel to the installation vessel, which immediately proceeds with installation operations.
This approach offers several advantages for windfarm construction projects.
First, installation vessels remain on site for longer periods, significantly reducing non-productive sailing time. Because installation vessels are among the most expensive assets in the construction process, maximising their operational time can greatly improve project economics.
Second, feeder vessels provide greater logistical flexibility. Multiple feeder vessels can operate simultaneously, creating a continuous supply chain of turbine components. This helps ensure that the installation vessel always has the necessary components available when weather conditions permit installation.
Third, the feeder concept can reduce pressure on port infrastructure. Because feeder vessels can shuttle components more frequently, ports may not need to accommodate large installation vessels as often. This can simplify port operations and reduce congestion. Another advantage of feeder-based windfarm construction is scalability. As offshore wind farms become larger and turbines become heavier, installation campaigns may require more sophisticated logistics strategies. The feeder model allows developers to adjust the number of feeder vessels according to project size and installation speed.
The concept also helps address one of the industry’s emerging challenges: the limited availability of next-generation installation vessels capable of handling very large turbines. By using feeder vessels, developers can make more efficient use of the installation vessels already available.
The Feederdock concept
At the core of the concept is a U-shaped jack-up installation vessel equipped with a large crane capable of installing next-generation wind turbines and foundations. Instead of loading turbine components directly at port, the installation vessel remains offshore while feeder vessels or barges transport the components from port to the installation site.
A key innovation of the Feederdock concept is the docking process. The feeder vessel carrying turbine components enters the open U-shaped structure of the installation vessel and docks inside it. Once connected, the installation vessel jacks up above the sea surface while the feeder vessel remains secured within the structure. This configuration effectively turns both vessels into a single stable platform.
This arrangement enables a “fixed-to-fixed” lifting operation, meaning turbine components are lifted from a stable feeder deck to a stable installation platform. This avoids complex and risky “floating-to-fixed” transfers that occur when components are lifted from moving vessels at sea.
By separating transport and installation tasks and allowing feeder vessels to shuttle components continuously from port, the Feederdock principle can shorten installation campaigns and improve logistics efficiency in offshore windfarm construction. (1)
Although feeder-based installation is still evolving, it represents an important step toward more efficient windfarm construction. As offshore wind projects expand into deeper waters and more remote regions, advanced logistics concepts such as Feederdock may play a key role in enabling faster, more cost-effective deployment.
Behind every successful windfarm construction project is a large and highly skilled workforce operating both onshore and offshore. The scale of modern offshore wind projects means hundreds, and sometimes thousands, of professionals may be involved during construction.
Many of these workers operate offshore on specialised vessels. Marine crews are responsible for navigating installation and support vessels, maintaining dynamic positioning systems, and ensuring safe vessel operations in challenging conditions. Crane operators and rigging specialists play a critical role during turbine installation. These professionals manage the heavy lifting operations required to position towers, nacelles, and blades. Precision and coordination are essential, as turbine components must be installed with millimetre-level accuracy.
Wind turbine technicians are also present during windfarm construction. These technicians assist with mechanical and electrical connections inside the turbine and ensure that systems are properly prepared for commissioning once installation is complete. Engineers and project managers oversee the entire construction process. Their responsibilities include planning installation sequences, coordinating vessel schedules, managing logistics chains, and ensuring compliance with safety and environmental regulations.
Health and safety specialists are another essential part of the windfarm construction workforce. Offshore construction environments pose significant risks, including heavy lifting, working at height, and exposure to harsh weather. Safety teams ensure that strict procedures are followed and that all personnel are properly trained. Working offshore requires specific certifications and training programs. Many workers must complete Global Wind Organisation (GWO) training modules covering safety procedures, first aid, fire awareness, and working at heights. Maritime crew members must also comply with international maritime certification standards.
Offshore work schedules typically follow rotational patterns, such as two weeks offshore followed by two weeks onshore. During their offshore rotations, workers live aboard installation vessels or accommodation platforms, forming close-knit teams that must collaborate effectively under demanding conditions.
As offshore wind capacity continues to expand worldwide, the demand for skilled workers involved in windfarm construction is growing rapidly. Industry forecasts suggest that thousands of additional technicians, engineers, and maritime specialists will be required in the coming years to support new offshore wind projects. Investing in training programs, workforce development, and safe offshore working environments will therefore be essential for supporting the continued growth of wind energy (for more, see also: wind farm operations).
Windfarm construction refers to the process of building wind energy infrastructure, particularly offshore wind farms. This includes installing foundations, towers, nacelles, and blades, as well as laying subsea cables and connecting the wind farm to the onshore power grid.
The construction phase of an offshore wind farm typically takes one to three years, depending on project size, water depth, and weather conditions. Larger wind farms with hundreds of turbines may require longer installation campaigns.
Windfarm construction relies on several types of specialised vessels, including jack-up installation vessels, heavy lift vessels, cable-laying vessels, and support ships. In newer installation models, feeder vessels may also be used to transport turbine components from port to the offshore installation vessel.
Windfarm construction is becoming more complex as turbine sizes grow and offshore projects move further from shore. Innovative logistics models such as feeder-based installation can improve efficiency and accelerate project timelines. At the same time, the growing number of workers, vessels, and contractors involved in windfarm construction increases the importance of reliable safety systems. Electronic Personnel On Board (e-POB) solutions provide real-time visibility of offshore crews, enabling faster emergency response and better coordination between vessels and platforms. As offshore projects scale up, digital workforce tracking will play an increasingly important role in protecting workers during windfarm construction.
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Subsea cables are insulated power or communication cables installed on or beneath the seabed to transmit electricity or data across bodies of water. In offshore windfarm construction, subsea power cables connect individual turbines through inter-array cables and transport generated electricity to shore via export cables. These cables are typically buried or protected to prevent damage from anchors, fishing gear, or seabed movement, ensuring reliable long-term energy transmission in harsh marine environments. (2)
References:
(1) https://www.onp-management.com/onp/reference-and-press/feederdock/
(2) Hugh Rudnick (Ed.). Electric Power Transmission Systems. Academic Press, 2017. Chapter on submarine power cables.
Note: This article was partly created with the assistance of artificial intelligence to support drafting. The head image was generated by AI.