The design of LNG carriers has responded to market changes; next it will need to reflect dramatic increases in efficiency, writes ABS vice president, strategy and development Peter Fitzpatrick
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.
This, however, is not the case. On the contrary, the LNG carrier of 2030 will need to evolve further, reflecting prevailing 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 in the Energy Efficiency Design Index (EEDI) that whole marine industry will have to address, we may see some ideas coming to the fore.
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 maximise 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.
While there is little need for efficiency improvements on new LNG vessel orders before 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, CO2 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 (BOR) of 0.07% 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.
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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