Unboxing the ammonia-powered 15,000 TEU boxship: Seatrade and Foreship reveal key design features

Ammonia-powered container vessels are technically feasible and their development can meet acceptable preliminary safety concepts, according to the insights from a concept design study carried out by Maersk Mc-Kinney Moller Center for Zero Carbon Shipping, in partnership with Seaspan, ABS, and Foreship.

The project is connected to the Singapore Ammonia Bunkering Feasibility Study (SABRE) consortium, focusing on developing and demonstrating an ammonia supply chain in Singapore.

The design emerged earlier this year and the concept has already secured a green light from ABS.

However, there were a few design details revealed at the early stage of the concept development, and now the industry has been provided with a sneak peek into the future.

The design features a twin-island 15, 700 TEU ammonia-fueled containership, spanning 350 meters in length, a scantling draft extending to 17 meters, and a breadth of 53.6 meters, which might raise eyebrows.

The vessel can be described as rather wide having in mind the width of the Panama Canal, however, there is a reason behind this.

The heart of this vessel lies in its propulsion system, powered by a robust 90/92-bore dual-fuel Tier III ammonia engine, supplemented by four generators equipped to handle dual fuels for ammonia and conventional options.

The vessel also includes a plan for approx. 1,500 (1,000 on deck and 500 in holds) refrigerated container slots. It features all key energy efficiency design options rudder bulb, high-performance coating as well as ER fans, LED lighting, potentially a shaft generator, and a windshield installed on the deck aimed at reducing vessel drag.

In a strategic move, the ammonia fuel tanks are located below the accommodation, optimizing safety and practicality.

The decision to put the ammonia fuel tanks in this location was mainly driven by safety concerns due to the toxicity of ammonia. One of the key factors that led to this design was the fact that the hull form where the accommodation structure is located is particularly strong, reducing the chances of penetration or leakage.

The vessel boasts an impressive 11,600 cubic meters of ammonia tank capacity, with additional tanks of 4,600 cbm capacity for VLFSO, tucked away beneath the accommodation area.

When operating with conventional fuels, it consumes approximately 100 tons per day, a standard figure for a vessel of its size.

Ammonia, on the other hand, is a different beast, demanding a whopping 326 tons per day to maintain a cruising speed of 16 knots over 50 nautical miles due to its low energy density.

“Why are we going down the route of ammonia?” Seb Brindley, Senior Naval Architect, Seaspan Corporation, said during a recent webinar presenting the design while commenting on the considerable amount of ammonia the vessel will need.

“One key part of that is the fact that ammonia is a potentially scalable fuel. In order to create ammonia you just need nitrogen, water and energy input. When you burn ammonia, theoretically you should just be able to have a byproduct of water plus nitrogen so it is completely carbon-free.”

The choice of ammonia isn’t just about raw power; it’s a decision rooted in its potential scalability. By producing ammonia from nitrogen, water, and renewable energy, it holds the promise of a carbon-free future. However, it’s not without its challenges, including low energy density, the need for refrigeration at -33 degrees Celsius, and its toxic nature.

These include the strategic positioning of the accommodation structure, ensuring the ammonia tanks remain below, and thus, not encroaching on container slots. This design choice prioritizes safety and minimizes the risk of toxic leaks.

Seaspan is currently building twenty-three 15KTEU vessels in China and Korea, including ten that will feature dual-fuel LNG propulsion, and learnings from the design of these ships are expected to contribute to the company’s development of an ammonia-powered containership.

The vessel’s extensive endurance, boasting 18,500 nautical miles, positions it as a viable choice for future trade routes and pooling options on the Transpacific and Asia to Europe with expected ammonia bunkering available in Singapore.

“If we are only bunkering in Singapore, you would need to have an ammonia endurance of about 18,500 which would require a very large tank size. However, if we have a look at the requirements from a regulatory perspective, from the CII perspective, and at this early stage we can get a large endurance if we combine LSFO and ammonia. When the requirements become more stringent and we have to burn predominantly more ammonia, hopefully, the infrastructure of ammonia will become more widely available,” Brindley said.

With that in mind, the sensible ammonia endurance of this design would be 12,000 nm in one way.

Intriguingly, the vessel’s breadth extends beyond the Panama Canal’s typical limits, but there’s a reason behind this. Engineers found that the wider the vessel, the more containers it can carry, reducing fuel consumption per loaded container, a win-win for efficiency.

Moreover, its low slot cost, the measure of fuel consumed per loaded container, makes it an efficient and environmentally conscious choice for the shipping industry.

IMO type B ammonia tanks, known for their robustness and ease of monitoring, were selected. The tanks, positioned at the center of the hull, further minimize the risk of ammonia leaks. Additionally, a comprehensive HAZID review was conducted to identify and address potential risks, ensuring that this cutting-edge vessel remains a beacon of safety at sea.

To ensure the highest standards of safety, an Approval in Principle (AIP) was awarded by the American Bureau of Shipping (ABS). This endorsement validates that the proposed concept aligns with safety and regulatory standards, instilling confidence in the vessel’s future operations.

The paramount safety objectives when dealing with ammonia in the maritime industry encompass several key aspects.

Firstly, there is a focus on limiting ammonia-toxic areas and hazardous zones while also reducing the exposure time of crew members working in these areas. This approach aims to minimize potential risks that could jeopardize the safety of individuals on board, as well as the integrity of the vessel and its equipment.

Equally important is the establishment of secure and suitable ammonia fuel supply, storage, and bunkering arrangements capable of receiving and containing the fuel without any risk of leakage.

Furthermore, vessel designs are rigorously engineered to prevent ammonia venting under all conceivable operational conditions, encompassing both normal and abnormal scenarios, even during idle periods. Venting is only permitted as an extreme measure under emergency conditions, underscoring the industry’s unwavering commitment to safety at all stages of ammonia usage.

Some of the key safety aspects integrated into the design of the vessel include the bunker station and its arrangement, fuel storage tank positioning, fuel system and preparation spaces, as well as the vapor handling systems.

Ammonia bunker stations have been located two bays aft of the accommodation, losing one row in hold due to the width of the station. They have been arranged both port and starboard, ensuring that the parallel body line is sufficient to ensure proper contact with the bunker vessel. This arrangement provides the shortest possible bunker line while still maintaining the required hazardous zone separation from the accommodation entrances and air inlets.

The bunker station is designed as a semi-close type with an open side towards the bunker vessel. Furthermore, a bunker station deckhead is envisioned to be reinforced to provide further protection from dropped objects. The bunker station will be provided with the full range of required safety features to deal with ammonia spillage and leakage and protection of personnel and equipment.

The engine room arrangement has also been meticulously examined, with a strong emphasis on safety concepts, including fencing and vent lines. Additionally, the location and integration of the ship systems have been reviewed, with specific attention to fire and gas detection systems and the pivotal water mist systems within ammonia-containing spaces.