Techno-economic assessment of low-carbon ammonia as fuel for the maritime sector

Abstract

Low-carbon ammonia has recently received interest as alternative fuel for the maritime sector. This paper presents a techno-economic analysis of the total cost of ownership (TCO) of a Post-Panamax vessel powered by low-carbon ammonia. We also calculate the annual increase in carbon tax needed to compensate for the increment in TCO compared to a vessel powered by very low sulfur fuel oil. The increment in TCO is calculated as function of propulsion efficiency to account for uncertainties in the thermodynamics of ammonia combustion for three different cost scenarios of low-carbon ammonia. We evaluate the benefits and drawbacks of hydrogen and diesel as dual fuel for three types of propulsion systems: a compression ignition engine, a spark-ignition engine, and a combination of a solid oxide fuel cell (SOFC) system and a spark-ignition engine. We incorporate three different cost levels for ammonia and a variable engine efficiency ranging from 35 % to 55 %. If the ammonia engine has the efficiency of a conventional marine engine, the increment in TCO is 25 % in the most optimistic cost scenario. SOFCs can reach a better efficiency and yield no pollutant emissions, but the reduction in fuel expenses in comparison to conventional combustion engines only offsets their high investment costs at either low engine efficiency or high fuel prices. The increment in TCO and reduction in GHG emissions depend on whether high combustion efficiencies, small dual fuel fractions, and low NO_x, N₂O, and NH₃ emissions can be simultaneously achieved.