Karl Henning Halse

The oceangoing bottom trawler is the largest vessel type in the Norwegian fishing fleet. It is important to the Norwegian economy but has a controversial position in the public debate. Fishers have always had to adapt to change, and innovation is generally seen as a way to do so. However, examining the design of the bottom trawler reveals that while there have been numerous incremental developments, the concept has not changed since its introduction to the Norwegian fishery in the 1960s. Supported by empirical evidence collected through 12 semi-structured interviews with senior representatives of firms in the trawling industry, this article presents the recent historical development of the design and factors influencing this development. An outlook on current challenges and opportunities is given, concluding that a completely new way of thinking is required to accommodate disruptive innovation on the bottom trawler.

The installation of the present wind farms Hywind Scotland and Hywind Tampen are both carried out by towing the fully assembled wind turbine from the assembly site in the Norwegian fjords to the final offshore site. In the present study an alternative installation method is proposed where the fully assembled tower is transported to the site on the installation vessel and mounted onto the preinstalled floating substructure (a spar buoy). The paper presents a brief outline of the design process for the proposed concept and gives an overview of the work done to evaluate variations of the installation vessel and the proposed lifting mechanism. The paper is a summary of the results obtained by a project team in SFI MOVE addressing marine operations related to installation of floating offshore wind turbines.

Offshore wind turbine blade installation using jack-up crane vessel is a challenging task. Wave- and wind-induced loads on the installation system can cause large relative motion between the blade root and the hub during the mating process. Currently, several numerical tools are used to analyze such critical global motion responses; however, the industry suffers from lack of experiments and full-scale measurements to validate the accuracy of these results. Consequently, a code-to-code comparison exercise becomes critical as it allows comparing different numerical tools for reliable prediction and verification of results. In the present article, a numerical model of the offshore wind turbine blade mating process using a jack-up crane vessel is developed in orcaflex, and a code-to-code comparison is performed against sima; both these tools are immensely used in the industry for modeling marine operations. Different comparisons are made between both the tools such as: (1) modal analyses of the jack-up vessel and the blade lifting gear, (2) time-domain analysis of the fully coupled installation vessel-crane-blade system, and (3) a comprehensive sensitivity study based on different seed numbers and simulation periods. The results of the study show a good agreement between both the tools with a deviation of less than 3% in terms of modal analysis and less than 5% variation in time-domain results. Further, the article provides modeling guidelines for the industry practitioners that heavily rely on both the tools for modeling marine operations.