Classification society DNV has awarded an Approval in Principle (AiP) to Chinese shipyard Zhoushan Changhong International and design firm CIMC ORIC for a 21,700-teu container ship concept capable of operating with alternative fuels, including ammonia.

The design was developed in collaboration with Mediterranean Shipping Company (MSC) and is intended to give shipowners flexibility in selecting propulsion systems, ranging from liquefied natural gas (LNG) engines to ammonia-fuelled main engines.

According to DNV, a key technical challenge addressed during the approval process was fuel storage. As no single tank solution currently exists for storing both LNG and ammonia in the volumes required for large container vessels, the design incorporates a dedicated oversized Type C tank for ammonia, positioned alongside established LNG tank technologies such as Type B/C or membrane systems.

The hull design incorporates a vertical bow, optimised stern and hull lines, alongside low-resistance coatings, high-efficiency propellers, and energy-saving hydrodynamic features. The design's fuel efficiency has been validated through computational fluid dynamics (CFD) simulations and model tests.

Yin Xunbin, General Manager of CIMC ORIC, said: "We are proud to have received an AiP for our 21,700-teu multi-fuel container ship, with a special focus on the ammonia-fuelled variant. This allows us to offer owners a wider range of fuel options."

He added that MSC's expertise in LNG dual-fuel vessels enabled the development of key design elements for the ammonia dual-fuel version.

Giuseppe Gargiulo, Head of Newbuildings at MSC, said: "Although LNG remains the most proven fuel for MSC to operate container ships at this time, the insights gained from this joint project will also help drive innovation for future efficient dual-fuel-powered container ships and allow MSC to follow future options and be open for other technologies."

The classification society said its specialists assessed the concept against DNV and international requirements, covering fuel systems, propulsion arrangements, and safety and mitigation measures for both LNG and ammonia.

Øyvind Pettersen, Head of Technical Centre China at DNV Maritime, said: "A modular design approach that accommodates customer preferences for different alternative fuels broadens the choices for the industry and could become a key factor in bringing more sustainable vessels to the market."

He noted that LNG is currently the most widely adopted alternative fuel, while ammonia is gaining attention as an option.

The container ship design has also been optimised for efficient hold utilisation and a high load-to-capacity ratio. A twin-island deck arrangement and revised foredeck layout allow additional 40-ft container bays while maintaining port compatibility.

As development continues, the partners plan to conduct more detailed engineering and safety studies, including ammonia mitigation measures, gas-handling systems, and full integration of the fuel systems.

An Approval in Principle is an independent assessment that confirms a concept design is technically feasible and does not present significant obstacles to future construction.