Naval architects, Knud E Hansen has released details of its latest series of LNG refueling vessels. The X-gas project is a series of innovative and unconventional medium-capacity liquefied gas / gas refueling tankers.

The flagship design of the project is a 126.5m vessel with a total capacity of 9,000m3, split between two Type-C tanks. The platform, however, is highly customizable and can be adapted to suit a range of tank capacities, as well as various containment systems, including membrane tanks.

The most unique feature of the X-gas platform is a low profile forward deckhouse. This allows the ship to approach and pull safely alongside cruise ships with lowered lifeboats. It also minimizes the need for ballast during cargo transfer, thus reducing operating costs. Finally, the forward deckhouse allows for larger cargo tanks without obstructing visibility on the deck.

To improve maneuvering and safety, the design includes two rear thrusters and two bow thrusters, as well as an automatic mooring system for mooring alongside.

It also features a new, extremely fuel-efficient diesel generator set and a propulsion unit consisting of one of the most fuel-efficient dual-fuel four-stroke engines available. An energy storage system (ESS) with a group of lithium-ion batteries that optimizes the engine load with reduced methane slip is integrated into the propulsion system. The batteries also provide all the power required during the transfer of cargo, which helps prevent emissions or exhaust fumes when refueling the vessel, a feature particularly important for passenger ships.

Evaporative gas from cargo tanks is captured and consumed in dual fuel engines and the excess energy generated can be stored in batteries. The waste heat from the engine cooling water is converted into electrical and thermal energy through a number of ORC (Organic Rankine Cycle) waste heat units. In a new approach, wasted energy captured during operation can be stored in accumulators and released as needed to drive the absorption chiller and reduce the electrical load on board. This approach brings energy efficiency to a very high level.

Another unique feature of the design is an aft “power bay” which allows the vessel to deliver loaded containers of fuel or stored electrical power to a receiving vessel. It also allows the vessel to provide fully charged battery banks to remote locations on land, where the current infrastructure does not allow sufficient power to be provided.