Cutting Capex and emissions in LNG bunker vessel design

Great ideas need great engineeering to make a real impact. 

“Everything began with ideas drawn on a napkin, which is where all innovation starts,” says Bård Norberg, Director and founder of gas technology company CGR Arctic Marine, who had an idea for a low-cost, low emission solution in LNG bunkering years ago, and turned to Kongsberg Maritime to make it a reality. 

CGR Arctic Marine’s 6,000m³ Liquid Methane Bunkering (LMB) vessel design, the LMB6000, will be fitted with a comprehensive Kongsberg Maritime equipment solution comprising propulsion, remote control, gas engines, electrics, energy storage and integrated automation. The solution also includes cargo tank instrumentation and a Custody Transfer System, designed specifically for LNG Bunkering vessels.

The vessel will use Kongsberg Maritime’s Information Management System (K-IMS) and can be connected to the cloud via KONGSBERG’s Global Secure Network. The K-IMS platform, widely used by the LNG carrier market, lets owners make use of their data through a suite of tools and applications. The remote connection is used by Kongsberg Maritime for Remote Services, which lets trained engineers remotely assess and deal with equipment issues. 

The first two vessels, due for delivery in spring 2023, are to be built in China for Kanfer Shipping AS, a Norway-based developer of small and medium scale LNG transport and terminal solutions to whom CGR has handed the rights to commercially deploy these LNG bunkering and distribution vessels.

The project’s genesis can be traced back several years. “I was involved in an LNG project at Meyer’s Neptun Werft Shipyard in Rostock, Germany, and I started to think about how to use today’s technology in the design of a low-cost bunker vessel, itself running on LNG, that would be able to efficiently supply LNG fuel with the smallest possible environmental footprint, the minimum of complexity and the lowest possible capital (CAPEX) and operational (OPEX) expenditures," says Norberg. 

Cutting CAPEX 

For the design, Bård opted for a 6,000m³ tank for 2600 tonnes of LNG, which would have sufficient capacity. A mono-tank design was chosen to keep weight and costs down, improve hull utilisation, and cut the amount of cargo-handling equipment.

“No compressors, no heat exchangers,” Bård says, “so CAPEX will be optimised in the building of these vessels.” There is also the potential to increase tank size by simply lengthening the hull: Bård has 7,000m³ and 8,000m³ designs under consideration.

The LMB6000's single tank has state-of-the-art spray foam thermal insulation technology. Bård estimates that this limits LNG boil-off to "no more than 0.12% per day."

Another key feature of the new vessel is an onboard cargo-handling plant, which uses the cryogenic gas recovery technology from which CGR derives its company acronym. Capable of combining cooling, reliquefication and gas recovery during loading, discharge and gas-freeing operations, the CGR process plant’s cryogenic condensation uses heat exchange with liquid nitrogen to handle and recover cargo boil-off sustainably. This negates the need to dispose of it via incineration, flare or GCU (Gas Combustion Unit). Any vapour gases are instantly re-liquefied in the heat exchange process.

CGR process plants operate using proven cryogenic gas recovery technology which has been in existence for 20 years, but this will be the first time it has been designed for and installed on a vessel. “The plant will handle any type of boil-off very rapidly,” Bård confirms, “with a capacity of three to four tonnes an hour.”

Choosing engines

“With LNG fuel, CO₂ and NO_X emissions are the lowest you can get, so I naturally felt that these vessels should use pure gas engines for power production, coupled with hybrid technology," says Bård.

The need for an integrated engineering solution brought Kongsberg Maritime into the picture. “I felt that KONGSBERG’s knowledge of electronic installations and our extensive experience with LNG carriers would make a perfect match,” Bård observes.

“We have been working very closely with CGR Arctic Marine since February last year to provide our input,” says Axel Andenæs, Sales Manager, Global Sales and Marketing, Integrated Solutions (OPU and LNG), Kongsberg Maritime. “The ship design is focused on simplicity, going for pure gas instead of dual fuel, which means fewer systems and lower costs. We’ve thought very carefully about the best way of configuring our hybrid technology to facilitate peak shaving, optimising the vessel’s energy production and consumption to avoid the running of auxiliary engines any more than is necessary.

“Another aspect of this is that the vessel will be able to bunker alongside a cruise ship to discharge and unload on battery power only, without the use of generators, so there will be no exhaust fumes emanating from the vessel and an absolute minimum of noise and disturbance.”

Optimal efficiency

The vessels will accordingly be fitted with Bergen C26:33 gas engines with CPM (Cylinder Pressure Monitoring) to stabilise engine performance, reduce component stress and improve reliability. The plug-in hybrid power system, meanwhile, will consist of modular lithium-ion battery packs and a redundant pair of 1,550kW pure gas generators. The battery packs will allow the generators to run at optimal efficiency and consume less fuel during manoeuvring, slow-speed and latency operations.

“When the batteries are empty, we can just start the generators and charge them in three hours, and they’ll be fully charged again,” Bård comments. “If we go alongside a terminal with fully charged batteries, we won’t need to run generators for loading the vessel. We’ll have enough energy to cover the entire loading operation, only starting the generators when leaving port and going to the discharging field. This vessel is not only designed for bunkering, but also for short-sea distribution.”

As an additional safety measure, Kongsberg Maritime’s liquid-cooled, small-footprint Energy Storage System (ESS) incorporates multiple safety barriers to prevent thermal runaway between modules.

Soft landings

Extreme manoeuvrability and accessibility were critical in order to conduct operations in narrow, constrained port waters alongside other craft. Kongsberg Maritime’s solution has been to install a bow thruster and a redundant pair of 360° Azipull thrusters, which can be operated by means of an independent Poscon joystick system.

“This makes operations more simple and far safer because we can execute soft landings to the shoreside and to other ships,” Bård says. “The risk of touching is basically avoided. Gas carriers going into ports or carrying out operations are normally assisted by tugboats, but our goal is to remove the need for these and limit port expenses by being able to operate safely and redundantly ourselves.”

Bård is in no doubt about that the vessel makes sound business sense. "Even when factoring in the added expenditure on propulsion and batteries, we’ll still be able to offer this vessel at a far lower CAPEX and OPEX than the competition,” he says.

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