Mitsui O.S.K. Lines (MOL) has secured an approval in principle (AiP) from ClassNK for the basic design of specialized vessels to joint and bury subsea power cables.
MOL is working with Sumitomo Electric Industries, Furukawa Electric and Nippon Yusen Kabushiki Kaisha (NYK Line) to develop fundamental technologies-including a new type of cable-laying vessel-as part of a project subsidized by the Japanese government's New Energy and Industrial Technology Development Organization (NEDO).
One of MOL's roles in this project is to develop technologies for cable jointing and burial vessels, and acquisition of AiP from ClassNK represents a major milestone.
Support vessels are needed to joint the cables that will be laid multiple times at sea - these are called jointing vessels. In addition, the cables are buried in the seabed to keep them from being damaged by vessel anchors, fishing nets, and so on.
This process is mainly carried out using remotely operated vehicles (ROVs), and the work vessel that serves as the mother ship for the ROVs and is responsible for placing the ROVs on the seafloor and retrieving it is called a cable burial vessel.
Power transmission lines must be reinforced to deliver electricity from wind power generation sites, such as those in Hokkaido, to distant major consumption centers. Long-distance subsea DC transmission is regarded as a promising solution for efficiently transmitting large volumes of power, and it is considered effective not only for power grid development but also for offshore wind power generation.