Ascend to the Top: Exploring the Methods of Accessing Offshore Wind Structures

Getting to an offshore wind structure can be a complex and challenging task, especially when dealing with the harsh conditions of the open sea. Over the years the offshore wind industry has developed several different methods to transport workers to and from the wind structures, each with its own set of advantages and disadvantages.

One of the most common methods of accessing oil & gas offshore structures in the past is through the use of helicopter transportation. Helicopter transportation is very quick, allowing workers to reach the offshore (wind) structures in a short amount of time from the shore based heliport to the offshore structure. The popularity of the helicopter however s strongly decreasing due to following considerations.

The helicopter can not be used in the fog which limits the possibilities. Hand’s on tool-time is negatively influenced by the travel time to the heliport and in addition the 2 hours minimum time needed to arrive at heliport prior to flight time. Also flight delays and cancellations are considered giving a significant negative impact on the efficiency of helicopter operations. The helicopter also require specific training for underwater helicopter escape. The helicopter is also significantly more expensive as other options.

CO2 emissions are much higher and furthermore there have been various accidents with helicopters which raises concerns on the safety of this method of offshore access. In offshore wind the use of helicopter is mainly limited to medical assistance.

Another method of accessing offshore wind structures is through the use of small boat transportation from shore also known as CTV or Crew Transfer Vessels. The technicians overnight ashore. This method is typically used when the wind structures are located in relatively shallow waters and near shore wind parks. It is generally considered to be the cheapest option, but it is limited in operations. The limitations of CTV are calm seas up to Hs 1.3 meter as well limitations on distance traveled, windpark placed beyond 10 miles offshore are too far away for CTV operations.

As example is working day start at 0700 hrs till 1900 hrs, 3 hours of CTV transfer to arrive to the turbine, 5 hours work followed by 3 hours return trip to CTV port. From CTV port to hotel and back 30 minutes leaves from a 12 hour day only 5 hour working on the turbine remaining, the hand’s on tool-time is limited. The newer Offshore Wind Farms are located further offshore as 10 nautical miles and as such CTV operations direct to shore are seen reduced use. Another option for CTV use is in-field services where the CTV’s are sailing between the SOV’s equipped with boatlanding, boatlanding is sort of docking station where small CTV can dock or temporarily connect with SOV (Service Offshore Vessel) to allow technicians to transfer from or to the SOV.

Walk-to-work solutions, also known as motion compensated gangways, are becoming increasingly popular in the offshore wind industry as a way to safely and efficiently transport workers to and from offshore wind turbines. The motion compensated gangway is installed on an SOV (Service Offshore Vessel) On the SOV, the technicians stay for period of 4 weeks, including on board sleeping and eating. Facilities on the SOV are available for relaxation such as cinema, gym. The technicians stay on board, in the morning at 0630 breakfast can be eaten, at 0700 the technician can walk from the SOV alongside wind turbine directly onto the turbine to start its work before 0800.

The SOV vessel will arrive in the evening again and hand’s on tool-time of over 10 hours per day per persons can be reached with this working method. The costs are low, the safety is very high and the CO2 emissions are low. As this method ticks all the right boxes this access method is rapidly increasing its popularity compared to other solutions. Overall, the method of accessing offshore wind structures will depend on a variety of factors, including the location of the specific Offshore Wind Farm.