Abstract
The trend to replace internal combustion engines with electric zero-emission drives, visible in the automotive industry, also exists in the shipbuilding industry. In contrary to land vehicles, the requirements for the electric propulsion system of tugs are much greater, which combined with the limited space and energy on board, makes any amount of energy valuable. Strategic changes in the policy of many countries, such as the “Fit for 55” package, introduce plans to significantly reduce CO2 emissions, which favors the development of alternative drives and their introduction to new areas of operation. This article presents that it is possible to reduce the amount of energy an electric tug spends for movement by applying the Particle Swarm Optimization method to modify the shape of its hull. A statistical analysis of public data was performed to determine the speed profiles of actual port tugs. The Van Oortmerssen method was used to determine the hull resistances of the proposed tug and the impact of the hull shape modification sets on reducing these resistances. Based on the six obtained speed profiles, it was determined that one of the tested variants of modifications made it possible to reduce energy consumption on average by 2.12%, to even 3.87% for one of the profiles, and that some modifications increase energy consumption by even 6.59%.
Highlights
This article assumes that the tug in question will be a zero-emission tug, equipped with an electric energy storage based on LFP cells, which, through inverters, will power two electric propulsion motors that transmit their torque to thrusters
This publication presents the results of research related to the optimization of the hull shape of an electric port tug
Based on the statistical analysis of the speed profile data of typical port tugs, it was shown that the optimization of the shape of the tug’s hull can contribute to the reduction of energy consumption by 2% to approximately 3.8%
Summary
In an all-electric ship, the following components are redundant: fuel tanks, lubricating oil tanks, massive cooling installations and mechanical transmission systems such as reduction gears and drive shafts In their place, it becomes possible to install an electric energy storage, which for maintenance purposes requires less space around it. It became possible to move some propellers from the stern to other places, e.g., to the midship or to the bow This allowed the distance between the thrusters to be increased, which made it possible to exert higher torsional moments on the hull of the tug, contributing to increased maneuverability of the vessel. Machines generally have greater precision in process control, possibly with such complex operations as the assistance of ships by tugboats during port operations Both aspects will change the hull structure of the tugs. This article assumes that the tug in question will be a zero-emission tug, equipped with an electric energy storage based on LFP cells, which, through inverters, will power two electric propulsion motors that transmit their torque to thrusters
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