Modeling and optimization of ship power complexes for large-tonnage transport vessels

Abstract

The tightening of carbon intensity requirements for the merchant fleet, established by the amendments to Annex VI of the MARPOL Convention and by the resolutions of the Marine Environment Protection Committee of the International Maritime Organization (IMO), has sharpened the problem of the coordinated selection of the composition and operating modes of the power complex of a large-tonnage ship. Design and operational optimization procedures have been developing largely independently, so a ship that is optimal by design criteria may fail the operational carbon intensity standard within a few years of service. The aim of this work is a quantitative assessment of the reserves for improving the energy efficiency of a large-tonnage transport ship by means of speed, configuration and propulsion-hull optimization on a single computational model. The author’s model of the power complex of a 74,850 dwt bulk carrier combines the approximation of the required power, the fuel balance of the main engine and diesel generators, and the CII calculation procedure according to the current IMO guidelines. Three configurations of the complex have been calculated; the transition from the basic to the combined configuration (speed reduction from 13.5 to 12.5 knots, shaft generator, propulsion and hull measures, shore power) reduces the annual fuel consumption by 25,3% and the annual CO2 emission by 7,217 t, moving the ship from rating E to rating C under the 2026 standard. Factor decomposition shows that the speed factor provides 71,7% of the total effect, while the shaft generator contributes no more than 1,1%. The leading role of operational decisions means that compliance with carbon intensity standards is achieved primarily by managing the use of already installed equipment and only secondarily by retrofitting the complex itself.