Developing a new power system solution for an offshore supply vessel

This thesis has been developed in cooperation with Vard Electro in Ålesund. The motivation for the thesis is to investigate solutions for reducing the fuel consumption for offshore vessels. It is put effort in studying today’s operation of such vessels, and from this find where the potential for savings lies. In addition to better economy, reduced consumption improves the environmental profile, which is important in the industry today. The thesis is thereby bisected. The first part focuses on the situation today. In the second part, changes are suggested and compared to the findings in the first part. An analysis is performed of a data base with load history for a real offshore supply vessel. Data from six months of operation is studied aiming to get an insight in how efficient the configuration and usage of the power production system is. For different operational modes - harbor, transit, station keeping and manouvering - load, fuel consumption and the correlation between these are studied. The main tool in this work is Matlab, and a number of explanatory figures is presented. The analysis indicates that there is a potential for reducing the fuel consumption. Some changes are suggested to achieve this. The changes concern the number of generators, ratings of each generator, and control of generator allocation. Three different configurations are suggested, with four, five, and six generators respectively. A simulator is developed to perform tests on the suggested changes. The simulator excludes the dynamics of combustion engines and generators, but focuses on long term fuel consumption. Control of generator allocation is also included in the simulator. This is based on minimization of a cost function based on real costs for power production. The simulator is validated through testing against data from the data based previously studied. The suggested configurations of the power system show potential for reduction of consumption. Also changing the generator allocation control shows a considerable reduction compared to that of the real case study. It is indicated that the consumption can be reduced by as much as 10% by doing changes that optimizes the layout and handling of the power system according to the ship’s actual needs through a longer working period.