Membrane-type Fuel Tanks for Ships Saves Cargo Space

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  • Replace conventional C-type tanks with membrane-type tank.
  • LNG membrane tank solution pays itself back in less than 3 years.
  • Long voyages will become more feasible for LNG carriers.

Deltamarin along with Gaztransport & Technigaz (GTT), an engineering company involved in membrane containment systems for transport and storage of LNG, has studied the use of membrane-type tanks on cargo and passenger vessels. They are trying to revolutionize LNG vessels by replacing the conventional C-type tanks with membrane-type tank developed by GTT.

Deltamarin has created a unique portfolio of cargo and passenger vessels to save valuable cargo space compared to classic cylindrical-type LNG tank solutions and to enable the use of LNG for long ocean voyages. The portfolio includes a container vessel, a pure car and truck carrier (PCTC) and a cruise ship. During the development project, each of the vessels was equipped with a modularised GTT membrane tank type solution, which can be adjusted in size from 1,000 to 5,000 m³, depending on the case vessel. Either one or multiple tanks can be integrated into the vessel. The final fuel capacity is a trade-off between desired cargo capacity and bunkering intervals.

As an example, a container ship case vessel with a 2,500 m³ tank offers an autonomy time of 22 days or can reach 10,000 nautical miles. These figures ensure that most intra-Asian, intra-European or intra-American trade loops can be sailed in just one bunkering operation. Calculations made during the development project showed that only 60% of the LNG capacity provided by membrane technology could be accommodated in the same space, when using an optimised bi-lobe C-type tank solution. For large fuel capacities, therefore, the membrane solution is clearly the most feasible LNG fuel tank solution.

The Financial Viability

A financial scenario calculation was carried out with the following input parameters in which distillates (MGO) has been defined as a reference level:

Case vessel: 8,000 CEU PCTC
Required LNG endurance: 15,000 nm
Operation profile: 5 trips/year (Asia – Europe route)
Other alternatives: Use of MGO, HFO + scrubber, LNG Type-C tank
Fuel price scenario: MGO 600 $/tonne
HFO 400 $/tonne
LNG 350 $/tonne
Price for CEU slot per voyage: 800 $

As the figures indicate, in this case the LNG membrane tank solution pays itself back in less than 3 years compared to the reference level, whereas HFO with the scrubber option offers slightly shorter payback time.

From a Net Percent Value (NPV) point of view, the LNG membrane solution offers the highest value of all options over the ten-year period. This is due to the savings made by both, in LNG fuel price and efficient use of hull volume for LNG fuel tanks. Compared to Type-C tank solution, a significant amount of valuable cargo space inside the hull can be saved. The HFO option also has moderate fuel costs but is penalised because of the extra power and sludge handling required by the scrubber operation. With the fuel price scenario used, operating with MGO almost doubles the operating cost over 10 years compared to LNG options.

Trusted Solution for all routes

Thus, Deltamarin is now equipped to provide an extensive solution for LNG as fuel with the GTT Membrane tank which is a proven solution for most LNG related problems. With this new facility in place, long voyages will become more feasible for LNG carriers.

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Source: Deltamarin

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