With a focus on safety and cargo capacity
The maritime industry is undergoing a green transformation driven by the urgent need to reduce GHG emissions in line with the Paris Agreement. Among the various alternative fuels under exploration to replace conventional fossil-based fuels, ammonia is a promising candidate because of its long-term potential for zero carbon emissions.[1] As a carbon-free molecule, ammonia offers numerous advantages as a maritime fuel. When produced with renewable energy (e.g., e-ammonia), ammonia reduces well-to-wake GHG emissions by up to 97% compared to low-sulfur fuel oil.[2] With that said, emissions from the combustion of ammonia are still under study, and their environmental impact is uncertain.[3]
Despite these advantages, the adoption of ammonia as a maritime fuel poses several challenges, including:
Ammonia toxicity, corrosivity, flammability, and significant safety risks to humans and the environment.
The need to understand and evaluate the various risks,including those associated with human factors. This evaluation enables the implementation of appropriate design and operational safeguards early in the design process, which encompasses both engineering and administrative controls, to reduce risk to ‘as low as reasonably practicable’ (ALARP).
Careful handling of ammonia onboard, together with robust safety measures and procedures to manage risks.
Technological infrastructure and equipment onboard are still under development, and key components, like auxiliary combustion, need further advancement.
Larger space allocation for ammonia fuel storage (2.94 times higher volumetric ratio per unit heating) because of ammonia’s lower volumetric energy density (0.696 t/m 3) compared to marine gas oil.[4]
In this context, the ship design process plays a vital role in technically qualifying the ammonia pathway across the value chain by highlighting areas that require focus. At the MMMCZCS, we leverage ship design case studies to address technical challenges and opportunities and to help drive regulatory policymaking and verification.
This report builds on our previous efforts and introduces a concept design for an ammonia-fueled container feeder vessel, incorporating modular knowledge acquired from these previous studies. The report addresses two principal questions about the design of an ammonia-powered vessel:
What are the key technical considerations when designing an ammonia-fueled container feeder vessel?
Ammonia tank capacity and location of key items (accommodation, bunker station, ammonia tank, FPR, vent mast, and ventilation outlets from ammonia spaces)
What are the technical safety barriers needed to make the vessel safe enough for the crew?
Separation of ammonia spaces
Safe distance to outlet of ammonia vapor if a leak occurs
Physical barriers
Drain systems
Water screens and ammonia release management systems (ARMS)
Considering these factors, this report presents a detailed concept design of a 3,500 TEU container feeder, developed with a focus on ammonia system design principles. The concept design was optimized to achieve the required safety level while also limiting reductions in cargo capacity. As a result, this design concept marks an advancement in technically qualifying ammonia as a viable maritime fuel.
Although the concept design is an important first step in qualifying a fuel pathway, the final design and operational details must ultimately deliver a safe vessel. We addressed this aspect early in our design process with reference to the technical safety barriers listed above. We confirmed the concept design’s ability to achieve an acceptable safety level through a HAZID, hazard and operability study (HAZOP), and QRA. These processes have resulted in two Approvals in Principle of the concept design awarded by ABS and Lloyd’s Register (LR).
A strong focus in the publication is our safety approach and how risk to the crew from ammonia fuel is minimized in our design, as well as how we optimize design decisions to support both safety and space utilization on board the vessel.
Examples of safety decisions include:
Dividing fuel preparation areas into smaller independent rooms to limit crew exposure during a leak.
Positioning vent and ventilation masts based on fluid dynamics analysis to minimize exposure risk.
Equipping the ammonia storage tank with a full secondary barrier, insulated inter-barrier space, pressure contol systems, and dual reliquefaction plants.
By sharing this design and knowledge as an example of what is feasible even in the early phases of ammonia deployment as a marine fuel, we aim to build confidence in alternative fuel pathways and the maritime green transition.
