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Tuesday, May 26, 2020 

According to classification society DNV GL, with the current focus on alternative marine power sources, it is easy to overlook the overwhelmingly dominant position of the internal combustion engine (ICE) in marine propulsion.

The class society believes that the marine two-stroke ICE is so well proven and so well established that it will continue to have a central place in ship propulsion for decades to come. To meet decarbonisation demands, then, the question becomes one of fuel: which fuels can be green enough, and available soon enough, to satisfy stricter emissions regulations, and how will engine makers adapt to the new norm of fossil-free fuel?

“All the big engine makers are looking at alternative solutions, everything from energy sources to engine technology,” said Christos Chryssakis (pictured), Business Development Manager, DNV GL – Maritime. Chryssakis believes that internal combustion power will be the dominant force in shipping for the next 20–30 years, which he sees as the timeline to develop and commercialise alternative power solutions.

9“In the meantime, if we manage to find good alternative fuels, ICEs can compete,” says Chryssakis. “The big two-stroke engines are close to efficiency limits, but gains can be made in other energy efficiency technology that will open the way for smaller engines consuming less fuel.”

DNV GL quotes Kjeld Aabo, Director New Technologies, MAN Energy Solutions, who said: “We have more than 25,000 two-stroke engines operating, and more than 300 orders for alternative fuel engines. Right now there is no better power solution for ships of 2,000 dwt and above.”

Chryssakis says that the first step is for shipping to achieve critical mass in low-carbon fuels to reach the IMO emissions targets for 2050. “Some of this will be achieved through efficiency measures, but the rest will have to come from alternative fuels,” he says. "We are now updating our energy transition model based on the latest learning and regulations. Alternative fuels have to be produced with renewable energy and in a sustainable manner or they will ultimately not help to reduce the overall carbon footprint.” Ammonia is one fuel alternative steadily attracting more interest in the industry, as a good way of storing hydrogen, but one which has particular handling requirements, being both toxic and corrosive. "Existing class rules for ammonia as a cargo and as a refrigerant are a good starting point for developing rules for ammonia as a fuel, says Chryssakis, "but emissions still represent a challenge."

Another potential problem is emissions from combusted ammonia, which may contain a high amount of nitrous oxide, a powerful greenhouse gas, as well as uncombusted ammonia, which can iteslef be danerous in quantity. “We might be able to clean this exhaust, but the technology is not proven,” said Chryssakis.

Burning hydrogen in combustion engines is another option, according to Chryssakis, particularly if used to partly replace LNG in combustion engines, thereby reducing their carbon footprint.

Regarding biofuels, Chryssakis said: “Large-scale production, including facilities, has not performed well enough to justify realisation, either economically or technically. For example, if it takes 50 years for a forest to mature, and only 2% can be harvested annually if we are to ensure regeneration.”

Synthetic fuels too will need to be produced from renewable sources in order to qualify as green. “The issues right now are scaling up production, and identifying suitable energy sources,” said Chryssakis. “For example, it has been estimated that we would need 8 km2 of solar panels to produce enough ammonia to operate one large container vessel for a single year.”

Despite its status as a fossil fuel, Chryssakis believes LNG should not be discounted as a short and medium-term solution. “LNG can contribute a 15%–20% greenhouse gas emissions reduction, and it can also serve as a basis for using other fuels in the future. Evolving engine technology could also reduce methane slip from LNG.”

Chryssakis warns against delaying until we have the 'perfect' solution. “But we cannot bet safely today on a solution that will not be available until 2035 or 2045. It is better to work with what we have, and concentrate on building a future-proof infrastructure that can match future ships.”

Chryssakis notes that current battery technology is approaching the physical limits of energy storage. “New storage chemistries may emerge that can offer tenfold improvement, but they are still not proven on a commercial scale, and probably the first applications will be seen in automobiles, not large units like ships,” he said. "Fuel cells... perform better under constant loads, so they need batteries to even out consumption.” He notes that fuel cell life expectancy remains a significant variable.

The relative attractiveness of different power solutions will vary between segments as well, Chryssakis says. “For example, cruise passengers might be willing to pay a premium for cleaner ships. But how quickly are consumer attitudes changing in the same direction?” That being said, charterers and owners in the transport trade are becoming more attentive as consumer sentiment shifts towards green alternatives, and they are actively seeking alternatives, he confirms.

“Right now we are still in the phase where we need to explore all available options for ICEs. The most important thing is not to close doors too early. We can experiment today with what is available until the best alternative emerges,” Chryssakis concluded.

Aabo agreed: “There are so many balls in the air now that stakeholders are facing very complicated decisions. We know that ICEs will provide the highest efficiency possible in the foreseeable future. Unless something completely unexpected turns up, ICEs will be around for many years.”

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