Thermodynamic Analysis of an Ammonia Fueled SOFC System for Maritime Applications
Authors: Reiter Bernd , Hauth Martin 
Published: July 2021

Transporting goods around the world with ships is nowadays the most cost-effective solution and due to this reason, more than four-fifths of the entire global trade by volume is carried out by sea. This leads to the estimation concerning emissions of the International Maritime Organization (IMO), that international shipping was in 2014 responsible for 2,2% of global annual CO2 emissions and that these emissions could increase between 50% and 250% by 2050. Besides the CO2 and greenhouse gas (CHG) emissions ships, which are conventionally fueled with heavy fuel oil (HFO) or marine diesel oil (MDO), also emit nitrogen oxides (NOx) and sulphur oxides (SOx). These emissions and especially the SOx emissions are regulated by the IMO in the International Convention for the Prevention of Pollution from Ships (MARPOL: Annexe VI). Because of these regulations and more stringent self-imposed targets of several nations and organizations, the demand for alternative fuels and propulsion systems for the maritime transport sector is increased significantly. [1] [2] [6]

In order to meet these and more stringent upcoming regulations, ammonia, which can be produced by renewable energy sources (green ammonia), is proposed as a potential fuel for the maritime transport sector. Beside the fact, that green ammonia would lead to no CO2 emissions, ammonia in relation to other renewable fuels can be seen as a balanced solution concerning the volumetric energy density and renewable synthetic production cost. Moreover, ammonia is advantageous compared to hydrogen, because of its lower cost per unit of stored energy, more widespread production, handling and distribution capacity and better commercial viability. But there are also some concerns and challenges for the application of ammonia as a ship fuel, namely the toxicity and the environmental impact. Therefore, some safety measures have to be established like shut-off valves in case of leakage and redundancy in the fuel supply line. Furthermore, one big concern of ammonia is the relative low efficiency value of the corresponding efficiency chain, when ammonia is produced via Haber-Bosch process, because of the production of the hydrogen as a basis for this process. For this reason, also the direct production of ammonia via proton ceramic electrolysis will be reviewed. [2] [3] [4] [6]

Because of the fact, that ammonia is not as practicable for any ship type, the load points for the simulation of the investigated propulsion systems are also described in this paper. Research shows, that ammonia as a fuel for container ships and bulk carrier is the most useful way of application. [3] [5]

For further investigations, the solid oxid fuel cell (SOFC) is chosen as the basis propulsion for the ship, because of the possible direct use of ammonia and its good efficiency compared to other systems namely internal combustion engine (ICE) or PEMFC. In detail, the aim is, to investigate by simulation (Matlab/Simulink) three possible solid oxide fuel cell (SOFC) architectures, which are fueled with ammonia, and to compare their thermodynamic efficiency for marine applications representative operation points. The simulation output is used to answer the main research question: [3]

How thermodynamically efficient are different SOFC system architectures for marine applications powered by ammonia?

An Outlook on testing of a 5 kW Lab System is presented to validate the simulative results.

[1] Serra, Patrizia; Fancello, Gianfranco: Towards the IMO’s GHG Goals: A Critical Overview of the Perspectives and Challenges of the Main Options for Decarbonizing International Shipping. University of Cagliari, DICAAR—Department of Civil and Environmental Engineering and Architecture, April 2020

[2] McKinlay, Charlie; Hudson, Dominic Antony; Turnock, Stephen: A Comparison of Hydrogen and Ammonia for Future Long Distance Shipping Fuels. IN: LNG/LPG and Alternative Fuels, 29th – 30th January 2020, London, UK

[3] de Vries, Niels: Safe and effective application of ammonia as a marine fuel. Master thesis, TU Delft and C-Job & Partners B.V. 2019

[4] Valera-Medina, Agustin; Xiao, Hua; Owen-Jones, Martin; David, Bill et al.: Ammonia for power. IN: Progress in Energy and Combustion Science 69, p.63-102, september 2018

[5] Kim, Kyunghwa; Roh, Gilltae; Kim, Wook; Chun, Kangwoo: A Preliminary Study on an Alternative Ship Propulsion System Fueled by Ammonia: Environmental and Economic Assessments. In: Journal of Marine Science and Engineering. March 2020

[6] Hansson, Julia; Brynolf, Selma; Fridell, Erik; Lehtveer, Mariliis: The Potential Role of Ammonia as Marine Fuel—Based on Energy Systems Modeling and Multi-Criteria Decision Analysis. IN: sustainability, April 2020