NO: DELENG / 2017 / 70663
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By Sea and Coast | 04/05/2021

Continuing evolution: the LNG carrier of 2030

The design of LNG carriers has responded to market changes; next it will need to reflect dramatic increases in efficiency, writes Peter Fitzpatrick, VP, Strategy and Development, ABS

While LNG carriers have a relatively short history, they have been subject to a continuous evolution in their design and operational parameters over the last decade.Many of the design changes reflect the natural maturity of the industry, others have come in response to technical, operational and regulatory changes.

With vessel sizes having standardised to serve installed terminal infrastructure and with a choice of containment and propulsion systems, it could be that the sector is set for a period of smaller, incremental changes.

In fact the LNG carrier of 2030 will need to evolve further, reflectingprevailing industry trends around the adoption of new technologies and more efficient operations to drive lower carbon emissions.Using LNG as fuel puts gas carriers on a clean fuel pathway but by 2030,in anticipation of required improvements inthe Energy Efficiency Design Index (EEDI) that whole marine industry will have to address, we may see some ideas coming to the fore.

So will the LNG ship of 2030 still have the design speed we see today? For an answer, it is necessary to look first at what we can expect from the key areas of the LNG vessel design and operation.

Emerging Technologies

The first of these key areas concerns the cargo containment system, as the continued need to reduce boil off gas (BOG) will be ever present as new ideas make the propulsion plant more efficient. Many owners have already adopted some sort of reliquefication capability but this concept will be essential in the LNG carrier of 2030, as dramatic improvements in insulation materials are not expected.

Although slow speed engines may still be the most efficient option available we can expect to see increased adoption of shaft generators, batteries and even fuel cells that all look to reduce the overall energy demand. Electric propulsion may again come back into favour on certain routes as the ability to plug and play batteries, fuel cells, gas turbines into the ships power system will provide additional flexibility, mitigating obsolescence risks, having the ability to upgrade a component without major changes to the ships power train.

Though hull forms may not change radically in the next decade, new ships will have to demonstrate compliance with the EEDI. While improvements in the traditional areas of naval architecture may be limited we will likely see ideas such as air lubrication, advanced antifouling and even wind propulsion becoming more common.

As with other vessel types, future gas carriers appear poised to be more connected, with increased use of smart technologies to collect and process data. This will enable a more efficient operation of ‘just in time shipping’ from loading to discharge that looks to maximize cargo delivery with the least amount of fuel consumed across the whole operation.

With further growth in spot trading, ships will need to be better connected and make greater use of operational data, voyage and fleet management technology. Connectivity of Operational technology will also increase to provide more inputs to optimise performance and maintenance schedules.

A future gas carrier is also likely to experience reduced methane slip as engine-makers increase mitigation measures. A more radical approach to efficiency could be active reduction of boil off gas with proactive insulation or sub-cooling of cargo.

Regulatory Drivers

While there is little need for efficiency improvements on new LNG vessel ordersbefore 2030, a large improvement – perhaps as much 30% - will be needed to comply with tightened EEDI requirements after 2030. To meet IMO emissions reduction targets requires a downwards trajectory arriving to 70% reduction by 2050, though some parts of the industry will go further.

This implies that in 2030 C02 emissions will need to be reduced by 21% compared with today. This might be achieved using an advanced waste heat recovery system, a power take off system and a 10% reduction of the power requirement.

This suggests that designers will have no option but to reduce design speed to meet the expected EEDI requirements, but other alternative technologies are emerging.Interpreting these changes in terms of LNG carrier design, if we believe that the minimum practical boil off rate of 0.07-6% per day has been reached, LNG carriers will generate more BOG than is required by the engines.

The result may be that a full reliquefaction system or a sub-cooling unit could be fitted as standard in future vessels. Another option could be to store the BOG energy in batteries and use it during the ballast journey. Either way, it is possible that BOG handling will be fully decoupled from the propulsion process. If this happens, it will be possible to blend in any ratio of bio or e-fuels as an emissions reduction solution rather than reducing ship speed.

Reducing speed alone will not necessarily reduce CO2 emissions from LNG carriers, as longer voyages could increase emissions and lower speeds could reduce overall fleet efficiency so the focus for designers and operators will be identifying the optimum balance between ship speed and CO2 emissions.

Even if the pace of change in LNG vessel design is slower in the next 10 years than it was in the previous decade, the pace at which technology is changing, combined with the increasing number of options becoming available over coming years means owners must still be prepared to evaluate and incorporate new techniques and technologies into future designs.

These need to be managed with the same focus on safety that has defined the LNG carrier market until now. By doing so, it should be possible to unleash a new wave of innovation that supports the industry’s trajectory towards further increases in efficiency and more sustainable operations.

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