As offshore wind farms move farther from shore, the challenge is not simply that vessels have to travel a longer distance.
For operations and maintenance, every extra hour spent sailing can mean less time working on turbines, higher vessel and fuel costs, and fewer opportunities to use short weather windows.
This is why Service Operation Vessels (SOVs) become increasingly valuable for far-offshore wind farms.

Travel Time Can Reduce Actual Working Time
Consider a maintenance team traveling by Crew Transfer Vessel (CTV).
If the journey takes one hour each way, two hours of the day are already spent in transit. If the one-way journey increases to two hours, four hours may be lost before loading, transfer, and weather delays are even considered.
So the important question is not simply: How many kilometers offshore is the wind farm?
It is: How much of the working day is being spent traveling instead of working on turbines?
As distance increases, this becomes a major logistics issue.

SOVs Replace Daily Commuting with Offshore Stay
The key advantage of an SOV is not only that it is larger. It changes the entire maintenance model.
Instead of personnel traveling: Port → Wind Farm → Port every time, an SOV allows them to remain offshore with tools, spare parts, accommodation, and support facilities nearby.
Daily operations can instead look more like: SOV → Turbine → SOV → Next Turbine.
The farther the wind farm is from shore, the more valuable those saved transit hours can become.

Distance Also Makes Weather Windows More Important
Offshore work depends heavily on suitable wind and wave conditions.
A short period of calm weather may provide only a limited opportunity for personnel transfer or maintenance. If a CTV is still traveling from port when conditions improve, part of that opportunity may already be lost.
An SOV already stationed near the turbines can respond more quickly and make better use of available operating windows.

Does Every Far-Offshore Wind Farm Need an SOV?
Not necessarily. The best O&M strategy also depends on wind farm size, port location, vessel speed, sea conditions, personnel requirements, maintenance demand, and cost.
Nearshore wind farms may still be efficiently supported by daily CTV operations. Larger and more distant projects may favor SOV-based strategies, sometimes combined with CTVs and other vessels.
So the growing importance of SOVs is not simply because they offer more facilities.
The real reason is that, once travel begins to consume too much working time, keeping personnel and resources close to the wind farm can become a more efficient way to operate.


References:
 • Guide to an offshore wind farm | An informative resource for offshore wind (Image source)
 • An Operations and Maintenance Roadmap for U.S. Offshore Wind
 • Index | Electricity | 2024 | ATB | NLR
 • Routing in offshore wind farms: A multi-period location and maintenance problem with joint use of a SOV and a safe transfer boat - ScienceDirect