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LNG carriers – the future is flexible

Thursday, 08 April 2021 | 00:00
As global LNG production continues to grow, the industry is turning its thoughts towards the next generation of carrier vessels that will underpin the supply chain for this vital energy source. In an era dominated by the drive for decarbonisation and efficiency, integrated powertrain solutions open up tremendous opportunities to develop flexible, future-proof LNG carrier designs that give owners and operators a vital competitive edge.

With the world’s need for energy continuing to rise at the same time as the competing need to focus on decarbonisation, the demand for LNG is growing. The wheels are already in motion in the form of several infrastructure developments for new LNG export and import terminals around the world, and shipyard slots being snatched up ready for the construction of the next generation of carriers that will form the backbone of the future supply chain.

“We will likely see anything from 100 to 150 new vessels being built in the next five to seven years to serve the burgeoning LNG production market,“ says Leonardo Ferrero, Senior Expert, System Development and Design, Wärtsilä Marine Power.

Spot the difference

At the same time, the LNG charter landscape is shifting, with a trend towards shorter-term agreements, explains Stein Thorsager, Opportunity Management, Wärtsilä Marine Power. “In the past charter contracts have typically run for around 20 years, meaning the carrier vessels are purpose-built for the charter in question. Today we’re increasingly seeing shorter-term agreements of perhaps seven to ten years as well as more spot-rate contracts, and this demands more flexible vessel concepts so that the asset can continue to earn its keep even after the original contract has ended.“

This trend is already shaping the approach to LNG carrier design, with more holistic, integrated thinking coming to the fore.

It’s time to step off the gas

Boil-off gas (BOG) is LNG that naturally evaporates and must be removed from the storage tanks in order to maintain the correct pressure. While boil-off rates have fallen significantly thanks to advances in containment-system technology, excess BOG that is not used to fuel the vessel still needs to be dealt with using an onboard liquefaction plant.

“Traditionally most charterers have had a target speed of about 19.5 knots, and this is the speed that the vessel design is optimised for,” says Ferrero. “Due to improvements in the insulation used in containment systems, less BOG is produced during laden voyages and hence less is available as LNG to fuel the vessel. Because of this we have seen a tendency for operational speeds to fall to somewhere around 16 knots on average, with a corresponding drop in fuel consumption. However, in spite of this reduction the charter agreements still maintain 19.5 knots as a contractual requirement, making speed flexibility a key target for LNG carrier designers,” Ferrero continues. As a result, Wärtsilä is continuing its efforts to optimise its vessel designs for lower speeds without jeopardising the ability to sail at 19.5 knots whenever there is a commercial advantage to do so.

Just as in the rest of the maritime sector, the drive to decarbonise is at the forefront of everyone’s minds in the LNG carrier arena too. “Vessels that can boast better environmental performance automatically gain a competitive edge in what is a highly competitive market because they can transport cargos in a more eco-friendly manner, which cargo owners are increasingly demanding,” Thorsager points out. Reaching this goal, however, requires a step change in the design and operation of these vessels.

A whole that’s greater than the sum of its parts

“As a marine technology provider, Wärtsilä has a key role to play as a provider of innovative integrated solutions for LNG carriers that will enable the industry to take significant steps forward in terms of vessel design optimisation and emissions reduction,” says Thorsager. “By taking an integrated approach we can make cumulative efficiency gains by incorporating the best possible combination of solutions,” explains Ferrero.

Wärtsilä’s offering for LNG carriers covers a wide range of integrated solutions, including those that reduce the need for propulsive power and improve onboard management of energy and BOG. They also include smart digital tools that improve vessel navigation capabilities, enhance voyage planning and the uptime of onboard systems and improve situational awareness for crews.

Two notable solutions that can reduce the need for propulsive power are the Silverstream® System – an air lubrication system that reduces the frictional resistance of a vessel’s hull – and the Wärtsilä EnergoProFin, an energy-saving propeller cap that improves propulsive efficiency. “The Silverstream® System can cut fuel consumption and emissions by as much as 8%, while the EnergoProFin offers average savings of a further 2%,” Ferrero continues.

A Wärtsilä shaft generator system provides an environmentally friendly means of generating both onboard electrical and propulsion power for LNG carriers during a voyage. This helps to reduce the running hours for the auxiliary engine and therefore overall fuel consumption and emissions.

Wärtsilä’s ESS battery-based technology offers a viable solution for vessels to implement new environmentally friendly functionalities. “We can combine a shaft generator with battery-based energy storage solutions in a hybrid system that enables the engine to run on optimal load while the batteries absorb any load fluctuations,” Thorsager explains. “This provides peace of mind by increasing the power redundancy and allows the engine to operate closer to its optimum design point where it has highest efficiency with the lowest specific fuel consumption and hence the lowest possible emissions.”

Wärtsilä’s Compact Reliq reliquefaction plant is a compact solution for reliquefying BOG. “A portion of the BOG can then be used as fuel while the excess can be reliquefied and returned to the LNG cargo tanks instead of being burned in a gas combustion unit,” Ferrero highlights.

Wärtsilä’s integrated offering also covers advanced combined inert gas generators and gas combustion units which reduce a vessel’s environmental footprint by using BOG to generate the inert gas needed for safe cargo-handling and maintenance operations.

Last but certainly not least, Wärtsilä’s range of intelligent digital solutions for integrated vessel navigation control, route planning and optimisation can be extended across an entire fleet. “For LNG carrier operators time is literally money. Our Fleet Operations and NACOS Platinum solutions provide a scalable, flexible way to ensure that the vessel consumes the minimum possible amount of fuel when sailing from A to B,” explains Thorsager. “This includes calculating the optimal speed and route to enable just-in-time arrival and the capability to adjust to any changes or delays along the way.”

A long-term commitment

Whatever the future may bring for the LNG carrier industry, Wärtsilä is ready to support operators with best-in-class expertise through its comprehensive lifecycle solutions offering, covering remote investigation and troubleshooting support, actionable advice and remote guidance for crews as well as data driven predictive maintenance services that combine artificial intelligence techniques and advanced diagnostics with Wärtsilä’s decades of expertise in marine technology.

As part of its long-term commitment to supporting vessel owners and operators, Wärtsilä also offers outcome-based agreements measured against an agreed set of KPIs such as fuel consumption, emissions and availability according to specific operational criteria.

“Wärtsilä’s integrated solutions for future LNG carriers offer a pathway for owners and operators to serve the LNG transportation chain in a way that will enable the IMO’s expectations for both 2030 and 2050 to be met,” Thorsager concludes.
Source: Wärtsilä

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