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Alternative Propulsions on the high seas

Letting the Current Move You

Cruise and container ships are among the world’s most important means of transport—at the same time, however, they produce enormous amounts of pollution, harming the environment. Shipping companies have been retrofitting to natural gas and hybrid propulsion little by little, but the longer-term goal is clean electric power. Is that even possible on the high seas?

Text Tino Scholz

The RMS Titanic, which remains the most famous cruise ship of all time, needed 640 tons of coal to power the ship—every day. The bunkers on the ill-fated ship, which sank in the North Atlantic after colliding with an iceberg on April 14, 1912, stored almost 7,000 tons of this fossil fuel. From today’s perspective, not to mention environmentally speaking, it’s nearly inconceivable. Meanwhile, although the era of coal-burning ships has passed, the topic of emissions has become considerably more important—and is the subject of intense debate.

Which is not surprising: five thousand container ships sail the world’s oceans day after day, transporting textiles, electronics and foodstuffs among the continents. Almost 90 percent of all goods are currently transported by sea. If things continue in this vein, by 2050 the amount of freight will triple. “Bigger is better” is also a maxim for cruise lines: while 15 million holidaymakers set sail in 2007, today nearly 26 million people are taking cruises. “Due to these enormous transport volumes, ships contribute a very large share of greenhouse gases and worldwide pollutant emissions,” says Christian Schneider, an expert for emissions-free propulsion systems at the German Shipbuilding and Ocean Industries Association (Verband für Schiffbau und Meerestechnik), headquartered in Hamburg, Germany.

Even today, the majority of ships run on heavy fuel oil, the cheapest and most sulfurous fuel. The International Maritime Organization (IMO) estimates that the world’s fleet emits more than a billion tons of carbon dioxide into the atmosphere annually—much more than is produced in all of Germany over the course of a year. However, global efforts to reduce climate-threatening emissions are having an effect on maritime industries. An initial tightening of regulations was recently pushed through by the IMO: accordingly, starting in 2020 ship engines will only be able to use fuels with a sulfur content of 0.5 percent, down from the current 3.5 percent.



The “Ampere,” in Norway, was the world’s first electrically-powered ferry when it set sail in 2015.

Compared to the fuels used to power cars on European roads, with a sulfur content of 0.001 percent, this is still a very high figure, but reaching a compromise in the seafaring shipping industry isn’t easy. “Maritime shipping is naturally a very international industry,” Schneider explains. “National interests often diverge.” Smaller countries in particular, including many in Africa, often hold a lot of power on the market and are fighting back against expensive, environmentally friendly upgrades. Despite this, carbon dioxide emissions are to be reduced by 10 percent every five years moving forward. This will inevitably lead to pressures for customers, shipyards and maritime supplier industries, with a view to retrofitting for cleaner propulsion.

The cruise industry in particular is already feeling this pressure. Vacation cruises on these ocean-going behemoths offer—depending on vendor—tranquility, relaxation, recreation or fun under the sun. With regard to the environment, however, these ships are among the biggest transgressors overall. In order not to dissuade environmentally conscious passengers, the big shipping companies are increasing investments in alternative means of propulsion. The American cruise company Carnival Corporation, which also owns Aida Cruises, is currently having a total of seven ships powered with liquefied natural gas (LNG) built in the coming years. In contrast to heavy fuel oil and diesel, burning LNG reduces nitrogen oxide emissions by up to 80 percent and carbon dioxide emissions by another 20 percent. Yet these changes take time: the technology still requires refining and the costs are also considerable. Experts believe that LNG-powered ships probably won’t gain greater acceptance from the side of industry until after the year 2020.

Yet Schneider sees considerable parallels between maritime industries and road mobility, although they’re several years behind the curve. The transition to cleaner natural gas variants should, in the best case, be followed fairly quickly by the next logical step: electric motors. “The parallels are evident, inasmuch as both industries, shipping and road mobility, are being driven to undertake more efforts to reduce emissions, greenhouse gases in particular,” Schneider says. “Due to its greater financial resources and the pressure to become greener for image considerations, the cruise industry is the trendsetter out on the oceans.”

New E-Ship

New E-Ship

The Elektra began operations in Finland in June 2017, powered by a multitude of battery packs. Diesel motors are available for emergencies.

But it’s a long and turbulent route to an e-ship—infrastructure being one of the major stumbling blocks. As such, a much-acclaimed project is really just a single milestone on the path to emissions-free shipping in the coming years. In 2019 Douro Azul is set to launch the world’s first purely electrically-powered river cruise ship, with space for 126 passengers and 40 crewmembers. The Portuguese shipping company is making a virtue out of necessity: because the tanks required to store LNG are extremely large, they cannot be used for river cruise ships. However, since the ships are always close to land, they can regularly dock to recharge their batteries.

In Europe and Asia there are already electrically powered ferries, and even solar-powered passenger catamarans, sailing across fjords, rivers and lakes. As Schneider explains, “For river cruise ships, which travel at much lower speeds than seagoing vessels, have far fewer passengers to cater to and are always near land where they can recharge batteries, battery-operated ships will certainly soon be competitive.” However, there is a qualification: “We have the same problem here that we do for road traffic: the charging infrastructure must first be made widely available. And that will take time.”

Experts in the industry therefore find it extremely difficult to predict what percentage of the market will be using electrically powered ships in the coming years. Developments in this area are too strongly dependent on a variety of factors, including environmental regulations and the market situation for shipping companies.

According to Schneider, seafaring cruise ships will have to rely on fossil fuels for the foreseeable future. “Such a ship is basically a small floating town, with enormous energy needs,” he says. “A big, purely electrically-powered cargo freighter, with its very long routes, is—considering the current state of technology—simply utopian.”