Abstract
The shipping industry is becoming increasingly aware of its environmental responsibilities in the long-term. In 2018, the International Maritime Organization (IMO) pledged to reduce greenhouse gas (GHG) emissions by at least 50% by the year 2050 as compared with a baseline value from 2008. Ammonia has been regarded as one of the potential carbon-free fuels for ships based on these environmental issues. In this paper, we propose four propulsion systems for a 2500 Twenty-foot Equivalent Unit (TEU) container feeder ship. All of the proposed systems are fueled by ammonia; however, different power systems are used: main engine, generators, polymer electrolyte membrane fuel cell (PEMFC), and solid oxide fuel cell (SOFC). Further, these systems are compared to the conventional main engine propulsion system that is fueled by heavy fuel oil, with a focus on the economic and environmental perspectives. By comparing the conventional and proposed systems, it is shown that ammonia can be a carbon-free fuel for ships. Moreover, among the proposed systems, the SOFC power system is the most eco-friendly alternative (up to 92.1%), even though it requires a high lifecycle cost than the others. Although this study has some limitations and assumptions, the results indicate a meaningful approach toward solving GHG problems in the maritime industry.
Highlights
Beginning in 2020, all ships have to meet sulfur regulation for the limit of 0.5% m/m in the fuel oil used onboard ships
A study by Nick Ash [3] concluded that green ammonia, which is produced while using renewable electricity not emitting greenhouse gases at any point in its product lifecycle, is a technically feasible solution for decarbonizing international shipping
Case 4, which is powered by hydrogen-based polymer electrolyte membrane fuel cell (PEMFC), has the highest fuel consumption, despite the hydrogen’s high energy density, which is generated from ammonia cracking
Summary
Beginning in 2020, all ships have to meet sulfur regulation for the limit of 0.5% m/m (mass by mass) in the fuel oil used onboard ships. In this regard, NH3 is being discussed as an alternative fuel due to its higher volumetric energy density and ease of handling. One of the companies in Denmark (RenCat) is commercializing technology to generate low-cost, high-purity hydrogen from ammonia, for use in fuel cells by replacing the traditional ruthenium-based catalyst with an iron-nickel alloy [30]. The novelty of this paper is that a new preliminary study on ammonia-fueled propulsion systems, which are promising de-carbonization solutions in the marine industry, are investigated from the long-term perspective.
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