Life cycle and cost assessment on engine selection for an offshore tug vessel

The objectives of this paper are to find the most cost effective and environmental friendly engine configuration and its application on an offshore tug vessel in aspects of cost-benefit and environmental impact. This aim was achieved by a comparison of two different engine configurations applicable to the propulsion system for a case ship, which is currently at design stage in a Turkish shipyard. Options of engine selections are to choose either two large medium speed diesel engines or four small high speed diesel engines connected to two gearbox and two shafts. A focus was placed on evaluating the cost-effectiveness and environmental-friendliness over the ship’s potential life ranging from construction to scrapping/recycling including operation and maintenance. Throughout the life cycle of the case ship, this study tracked the flows of cash, energy and emission associated with the cradle-to-grave process of such engines application to the case ship and quantified them as meaningful data for decision-making. Research findings clearly revealed that the application of four smaller engines to the subject ship is more advantageous than two medium engines in terms of cost and environment. In a general view, the results indicate that the option of multiple small engines provides high flexibility in engine operation according to various load profiles, therefore less energy consumption and emissions can be achieved.Contribution to the 17th International Congress of the International Maritime Association of the Mediterranean (IMAM 2017), October 9-11, 2017, Lisbon, Portuga