Kitting a barge out with cranes is no longer sufficient as wind-turbine installation (WTI) vessels are becoming increasingly sophisticated.

Water depth, size of the wind turbine and type of foundation all have to be factored into the design, says Germanischer Lloyd (GL) chief surveyor Norbert Kray.

Add to this specific requirements on speed — whether self-propelled or jacking — accommodation, lifting capacity and dynamic positioning (DP) and ships become very individual animals.