KNUD E. HANSEN X-gas Project Leads in Sustainable Fuel Transport

The X-gas Project is a series of innovative and  unconventional, medium-capacity Liquified Gas / Gas  bunkering tankers designed by KNUD E. HANSEN. The  flagship design of the project is a 126.5 metre vessel  with a total cargo capacity of 9,000 cubic metres, split  between two Type C tanks. The platform, however, is  highly customizable and can be tailored to accommodate  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 deck house. This enables the vessel to  safely approach and pull alongside cruise ships with low hanging lifeboats. This also minimizes the need for ballast  during cargo transfer, thereby lowering operational costs.  Lastly, the forward deck house allows for larger cargo  tanks without impeding bridge visibility. 

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

The design features a novel and extremely fuel-efficient  diesel electric power and propulsion plant consisting of  one of the most fuel efficient dual-fuel 4-stroke engines  available. Integrated with the propulsion plant is an  Energy Storage System (ESS) with a lithium-ion battery  bank that allows for engine load optimization with reduced  methane slip.  
The batteries also provide all of the power required during  cargo transfer, resulting in no emissions or exhaust in  way of the ship being bunkered, an especially important  feature for passenger vessels.

Boil-off gas from the cargo tanks is captured and consumed  in the dual-fuel engines and the energy surplus generated  can be stored in the batteries. Waste heat from the engine  cooling water is converted to electric and thermal power  through a number of ORC (Organic Rankine Cycle)  waste heat units. As a novel approach, wasted energy  captured during operation can be stored in accumulators  and released as required to drive absorption chiller and  reduce the electrical load onboard. This approach boosts  energy efficiency to a very high level.  

Another unique feature of the design is an aft ‘energy bay’  that allows the vessel to provide containers loaded with  fuel or stored electrical power to a receiving vessel. It also  allows the vessel to provide fully charged battery banks  to remote locations ashore, where current infrastructure  does not allow sufficient power to be provided.