Offshore wind farms need personnel to travel to turbines for inspections, maintenance, and other tasks.
Two common vessel types are the Crew Transfer Vessel (CTV) and the Service Operation Vessel (SOV).
Both carry people—but they are designed for very different operating models.

CTV: The Offshore Shuttle
A CTV is usually a smaller, faster vessel that carries personnel from port to the wind farm and back again, often within the same day.
Typical CTVs are relatively compact and may carry around a dozen or more technicians. They generally do not provide overnight accommodation.
At the turbine, a CTV often pushes its bow against the boat landing, allowing personnel to transfer onto the turbine access ladder.
This makes CTVs well suited to wind farms located relatively close to shore, where daily travel from port is practical.

SOV: A Floating Offshore Base
An SOV works differently. Instead of returning to port every day, it can remain offshore for days or even weeks. The vessel may include cabins, dining areas, workshops, storage space, and facilities for personnel living and working at sea.
SOVs are also commonly equipped with Dynamic Positioning (DP) and a Motion Compensated Gangway.
During a Walk-to-Work (W2W) operation, DP helps the vessel maintain position beside the turbine, while the gangway creates a controlled pathway for personnel to walk directly onto the structure.

Why Not Use SOVs for Everything?
Because greater capability also means a larger and more complex vessel.
If a wind farm is close to shore and only a small number of personnel need to travel out and back, a CTV may be the more practical option.
But as wind farms move farther offshore, daily travel can take up a significant part of the working day. In those cases, an SOV can reduce repeated journeys by keeping personnel, tools, spare parts, and accommodation directly within the wind farm.
So, CTVs and SOVs are not simply competing vessel types.
They support two different offshore logistics strategies.

A simple way to remember the difference is:
 • A CTV is like an offshore shuttle bus.
 • An SOV is more like a floating hotel and operations base.
Both bring personnel to offshore wind turbines—but they do it in very different ways.


References
 • Guide to an offshore wind farm | An informative resource for offshore wind
 • Crew Transfer Vessel (CTV): A Key Link in Offshore Wind Operations
 • Offshore Wind Service Operation Vessel (SOV): A Second Home at Sea for Wind Technicians