Abstract
This study develops system-level models of ammonia-fuelled powertrains that reflect the characteristics of four oceangoing vessels to evaluate the efficacy of ammonia as an alternative fuel in the marine environment. Relying on thermodynamics, heat transfer, and chemical engineering, the models adequately capture the behaviour of internal combustion engines, gas turbines, fuel processing equipment, and exhaust aftertreatment components. The performance of each vessel is evaluated by comparing its maximum range and cargo capacity to a conventional vessel. Results indicate that per unit output power, ammonia-fuelled internal combustion engines are more efficient, require less catalytic material, and have lower auxiliary power requirements than ammonia gas turbines. Most merchant vessels are strong candidates for ammonia fuelling if the operators can overcome capacity losses between 4% and 9%, assuming that the updated vessels retain the same range as a conventional vessel. The study also establishes that naval vessels are less likely to adopt ammonia powertrains without significant redesigns. Ammonia as an alternative fuel in the marine sector is a compelling option if the detailed component design continues to show that the concept is practically feasible. The present data and models can help in such feasibility studies for a range of vessels and propulsion technologies.
Highlights
The Paris Climate Agreement and similar country-specific policies set targets for decarbonisation across numerous sectors [1,2]
This study develops system-level models of ammonia powertrains to evaluate the use of ammonia as an alternative fuel in the marine sector
The results indicate that ammonia-fuelled ICE powertrains are better suited for implementation than ammoniafuelled gas turbine (GT)
Summary
The Paris Climate Agreement and similar country-specific policies set targets for decarbonisation across numerous sectors [1,2]. In 2008, the International Maritime Organisation (IMO) set a framework for decarbonisation focusing on short-, middle-, and long-term efforts [6]. Short- and middle-term efforts focus on improving the hydrodynamics, steaming speeds, and fuel efficiency of both existing vessels and the near-future fleet. Ammonia is an attractive energy vector for the marine sector because it is composed of only nitrogen and hydrogen, indicating that its combustion is carbon neutral. Pure hydrogen would require temperatures below 20.25 K to remain a liquid at the same pressure [16]. Ammonia production via fossil fuels is often accomplished by combining hydrogen generated by steam methane reforming (SMR) and pure nitrogen in the Haber–Bosch process. Green ammonia production typically takes advantage of the Haber–Bosch process but uses hydrogen generated via electrolysis with renewable electricity. Other novel methods for green ammonia production include algae conversion, latent thermal energy recovery, and other new and innovative solutions [17,18]
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