As the shipping industry moves towards decarbonization, ammonia has emerged as a promising low-carbon alternative to conventional fossil-based marine fuels. However, considerable work is still needed to make widespread implementation of ammonia-fueled shipping a reality. Development of safe and efficient ammonia-fueled vessel designs is a major part of this ongoing work. To date, most ammonia-fueled vessel design projects have specifically focused on small or gas carrier vessels. As a result, their findings may not directly translate to large deep-sea oceangoing vessels such as container vessels. To address this gap, this project initiated by Seaspan and the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping (MMMCZCS) set out to develop a design for a large ammonia-fueled container vessel.
Working closely with ship designer Foreship and classification society American Bureau of Shipping (ABS), we have jointly developed a concept design for a 15,000 twenty-foot equivalent unit (TEU) container vessel. This marks a significant milestone towards the potential commercialization of the ship design for Seaspan Corporation.
 Opportunities and challenges
During our design development, we have identified both opportunities and challenges, which can serve as a foundation for future ammonia-fueled vessel designs. Opportunities include:
- Achieving safety benefits through fully refrigerated ammonia storage.
- Optimizing the location and volumes of ammonia storage tanks to minimize container slot loss and reduce the risk of tank penetrations while ensuring the vessel’s endurance.
- Providing sufficient space for defined hazardous zones, separate spaces for ammonia-related equipment, and multiple access/egress points.
Certain challenges and uncertainties are already identified and must be approached with careful consideration during the upcoming design stage, as outlined in the table below.
The project’s completion of the vessel concept design development confirms the technical feasibility of large ammonia-fueled container vessels and their ability to achieve acceptable preliminary safety concepts. This has been convincingly demonstrated during the HAZID workshop and risk mitigation process, resulting in an Approval in Principle (AiP) awarded by ABS. Such a milestone boosts confidence in the advancement of the ammonia fuel pathway, unlocking its potential as a viable and eco-friendly option for maritime decarbonization. Nonetheless, despite these promising results, the next design stage demands careful consideration to effectively address the various known challenges and uncertainties that lie ahead, including the importance of human factors and change management in addition to technical safeguards.
For those interested in demonstrating the viability of the ammonia pathway, our concept design can provide an example of what is possible. For those designing ammonia-fueled vessels, we would like to highlight that while a high-level concept design is an important first step, the design and operational details will ultimately deliver a safe vessel. The MMMCZCS has recently published a report describing the results of a multi-disciplinary quantitative risk assessment study that suggests detailed safeguards to mitigate vessel design risks to tolerable levels. While some of these safeguards are clear, other details require further joint industry development and collaboration.
Gunnar Stiesch, the Chief Technical Officer at MAN Energy Solutions, commented, “This is a significant step towards creating a large-scale two-stroke ammonia marine engine. We’ve acquired a comprehensive understanding of ammonia’s distinct properties as a marine fuel and its impact on fuel supply and safety. This combustion achievement is yet another stride towards the marine market’s decarbonization and our goal of zero emissions.”
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