New generation of ice-breaking LNG carriers takes shape in Russia

Gas carrier design for multi-fuel future

With the LNG-fuelled fleet growing, new ice-class LNG bunkering vessels are also being conceived. Leaning into the multi-fuel future, Danish naval architectural and marine engineering firm Knud E Hansen has unveiled a flexible liquefied gas and bunkering vessel design that can accommodate LNG and zero-emissions fuels, such as compressed and liquefied hydrogen.

Knud E Hansen senior mechanical engineer Kim Nørby Christensen explained the idea behind the X-gas Project: “It will be able to transport almost any gas (liquid or compressed) for future fuels. When we mention hydrogen, we see it as the link in the power-to-x technology, as hydrogen plants are planned in many countries, but there must be a link like the X-gas to connect production plants and consumers.” This covers the carriage of CO₂ and ammonia, too.

Knud E Hansen’s X-gas Project is a series of medium-capacity liquefied gas supply and bunkering vessels, the largest of which would be a ‘flagship’ 126.5-m vessel with a total cargo capacity of 9,000 m³ for LNG, split between two IMO Type C tanks. The vessel will have a beam of 20.5 m, design draught of 5.25 m and deadweight of 4,775 tonnes.

The tank system, the top side equipment and the associated ship particulars will change depending on the application, “but we target almost all the gasses that the operator wants to carry, and we will take care of the necessary ship particulars for the request,” said Mr Christensen. He noted that with the variety of fuels under consideration for the future, and with the large differences in mass density and energy density, “we consider a brand like X-gas to be the right way to promote tankers under a common ‘umbrella’, here represented by the LNG ‘flagship’.”

Built with the notation Ice Class 1A, the liquefied gas transport and bunkering vessel would be capable of navigating in difficult ice conditions, with the assistance of icebreakers when necessary under DNV rules, or the equivalent Finnish-Swedish Ice Class 1A notation. Ice Class 1A vessels have thicker hull plating and ice-strengthened framing.

“[The X-gas Project] will be able to transport almost any gas, liquid or compressed, for future fuels”

Knud E Hansen says the X-gas platform can be built with different tank capacities and containment systems, including membrane tanks.

Notable is the vessel’s low-profile and forward deck house, which will enable it to safely approach and pull alongside cruise ships with low-hanging lifeboats. Additionally, this minimises the need for ballast during cargo transfer, lowering operational costs. Lastly, the forward deck house allows for larger cargo tanks without impeding bridge visibility.

For improved manoeuvring and safety, the design features two propulsion thrusters aft and two bow thrusters and an autodocking system for alongside mooring.

Propulsion for the vessel will be supplied by four-stroke, dual-fuel diesel-electric engines, and an energy storage system (ESS) with a lithium-ion battery bank for engine load optimisation. This will allow the vessel to operate on batteries during low load conditions – avoiding methane slip when operating on LNG. The batteries will provide all of the power required during cargo transfer or bunkering operations, resulting in no emissions or exhaust – especially important when refuelling passenger vessels. Service speed will be 13 knots.

Other energy efficiency features incorporated in the design are the use of boil-off gas in the dual-fuel engines, with the ability to store any surplus energy in the batteries. Waste heat from the engine cooling water is converted to electric and thermal power through a number of Organic Rankine Cycle waste heat units.