As the shipping industry searches for solutions to achieve decarbonization goals, one of the challenges is to develop a cost-effective solution to meet the large number of vessels in service. Two different groups presented proposed solutions which they believe can significantly reduce the cost of retrofitting a wide range of in-service container ships to use LNG and prepare for future alternative fuels such as bio-LNG or possibly new generation fuels such as ammonia.
While the container shipping segment has begun to develop LNG-ready vessels, the cost and time lost in service remains a hurdle to overcome. Hapag-Lloyd has completed the first major conversion of an LNG-ready vessel, the 15,000 TEU sajir, which was built in 2014 in anticipation of a future conversion. the the conversion took nearly nine months while the LNG tank was installed and the main engine and auxiliary diesel engines were retrofitted for LNG and low sulfur operations. In addition to the financial cost and downtime, the ship sacrificed an area equivalent to 350 containers by installing a 6,700 cubic meter gas storage system and the piping between the storage and the engine. Rolf Habben Jansen, CEO of Hapag-Lloyd, said that although the company had gained valuable experience in the conversion and continued operation of the vessel, the cost of modernization was prohibitive for the line to be able to use it widely in his fleet.
Marine Service GmbH and Newport Shipping believe they have developed an approach that will be simpler for refit, requiring less time and money while being easier to use. Their concept consists of containerized LNG cylinders in open frames the same size as existing 40ft containers. The bottles would be stacked on deck in the same way as current container stacks, handled through the same process as cargo containers, and secured through the same process. LNG containers would be fully portable so they could be loaded and unloaded with container cranes and swapped during full tank calls. The empties would be transferred to trucks for filling and could be stored at the port ready to load the ship on its next port call.
The LNG piping and ventilation system, as well as the fire-fighting systems, would be integrated into the structure of the container cell guides. The gas handling room would be arranged next to the container storage and separated from the containers by a cofferdam and means of protection against fire, allowing the supply of low pressure and high pressure combustible gas systems suitable for 4-stroke currents and 2-stroke twin-engine. gasoline engines.
LNG tanks would be exchanged at the port with the same equipment as containers (Marine Services / Newport Shipping)
The LNG fuel tank would be a type C LNG fuel tank homologated according to the IGF code and is based on an IMDG container certified by the German TÜV. The tank capacity is 31 gross tons and approximately 33m3 of LNG. Containers are equipped with a fail-safe dry quick coupler and are approved for loading in stacks of up to seven layers. The double-walled stainless steel tank is also vacuum insulated and has a shelf life of up to 80 days.
Another advantage of the rack system would be the ability to build the structure in advance at the shipyard. It could then be installed during a regularly scheduled dry-docking, reducing the time the vessel would be out of service. They noted that their design could also be used on new buildings instead of scarifying space in the hull for the LNG tank.
The companies report that they have identified up to around 900 container ships in service with a capacity of 4,000 TEUs and above that would be best suited for conversion. The system could be tailored to the specifications of the individual shipowner. Bureau Veritas worked with the contractors to review the designs and issued approval in principle for the containerized LNG solution.
The concept provides for the insertion of a section housing the LNG tank and the extension of the capacity in TEU (Alwena Shipping)
The alternative renovation concept, which also received an AiP from BV, was developed in partnership between Alwena Shipping, COSCO Shipping Heavy Industry Zhoushan shipyard and GTT. Their LNG conversion concept combines a lengthening of the vessel for very large container ships. They request the addition of a section to the ship’s hull that would contain the LNG tank and the necessary fittings to reduce wasted space and provide additional TEU capacity.
In this concept, the lengthening of the vessel combined with the conversion operation to LNG of the onboard propulsion and electrical generation system allows the reduction of the operating costs of the vessel in the future with the additional capacity and advantages of the LNG. They would limit the financial impact associated with the downtime required to modify the vessel, by constructing the new section in advance at the shipyard and making the necessary preparations for lengthening.