Analysing the Performance of Ammonia Powertrains in the Marine Environment

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.

Using ammonia as a shipping fuel could disturb the nitrogen cycle

“…In the future, upstream NH 3 emissions can be mitigated through technological change, increases in the prices of the product, or pricing on their emissions, but some non-zero quantity of emissions should be expected due to the nature of producing and transporting a commodity that is gaseous at standard atmospheric conditions. NO x emissions of marine ammonia engines have been addressed in the literature, though the uncertainties are significant, spanning two orders of magnitude [5]: from about 0.02-0.2%, which is similar to present marine diesel engines, to about 0.2-2% of the nitrogen in ammonia fuel becoming NO x [15]. Importantly, the estimates to this point are not based on observational data from ammonia ships operating in real-world conditions, as this technology is not deployed at present.…”

“…One solution that has been proposed to address these challenges is to use ammonia (NH 3 ) (made from renewable energy) as a shipping fuel source [3]. While studies address various benefits and costs of this technological strategy [4,5,6], none have assessed it in the context of the global nitrogen (N) cycle.…”

A Review of the Latest Trends in the Use of Green Ammonia as an Energy Carrier in Maritime Industry

“…Ammonia can be used as a drop-in fuel in diesel in internal combustion engines and gas turbines and as a primary fuel in fuel cells, making it a very appealing and competitive alternative [6,18,23]. However, as Imhoff et al suggest in their study, "naval vessels are less likely to adopt ammonia powertrains without significant redesigns" [29]. They further state that, if ammonia can be used as an alternative marine fuel, the powertrain design concept must prove that it is practically possible.…”

“…They further state that, if ammonia can be used as an alternative marine fuel, the powertrain design concept must prove that it is practically possible. Note that, in the study by Imhoff et al, the powertrain includes an engine, a waste heat recovery (WHR) heat exchanger (HX), an exhaust aftertreatment system, a fuel tank, a fuel heater, and an ammonia cracker [29].…”

Estimates of the Decarbonization Potential of Alternative Fuels for Shipping as a Function of Vessel Type, Cargo, and Voyage

“…Horvath et al [20] showed that hydrogen fuel would result in a higher cargo space loss of up to 13.3% for a short-sea vessel, which was contradicting to the 5% cargo loss reported by the International Council on Clean Transportation [21]. Imhoff et al showed that ammonia fuel could result in cargo loss between 4-9% [22]. In addition, some studies compared the performance of ships powered by different fuels.…”