SIEMENS

Danish shipping line Maersk and shipbuilder Daewoo are joining forces in South Korea to build the biggest ships in the world. These gigantic vehicles are 400 meters long, 59 meters wide, and 73 meters high. A basketball arena plus an American football stadium plus an ice hockey arena, each with thousands of seats for spectators, could all fit in the hull of one of these leviathans. Each of these ships will be able to carry as many as 18,000 standard containers – 16 percent more than the Emma Maersk, the biggest container ship now in service. According to Maersk, one of the new ships could transport 111 million pairs of sneakers, enough for all the inhabitants of Mexico.

But the ships of the new “Triple E” (economy, energy, environment) class will set standards in terms of more than just size. They will also be examples of energy efficiency and environmental friendliness. To achieve this, engineers have given particular attention to the propulsion systems. “The biggest cost in maritime shipping comes from fuel consumption,” says Kay Tigges, a marine engineer at Siemens. For example, when the Emma Maersk is transporting a full load it consumes around 14,000 liters of heavy oil per hour and pumps out over 40 tons of CO₂ – more than a five-member household in Germany generates in a year. So any savings pay off quickly in terms of both the shipping companies’ budgets and the environment.

Triple E class ships will therefore be equipped with a more efficient propulsion system with key components from Siemens. Two heavy-oil-powered engines with a total output of 86,000 hp will turn the two ship screws, each of which is ten meters in diameter and weighs 70 metric tons. The engines run more slowly than other marine propulsion systems and have a longer stroke; in other words, the pistons travel further in the cylinders. This reduces fuel consumption by between two and four percent. However, engine efficiency can be improved even further. “Today, about half of the energy released during combustion is lost as waste heat. So in the Triple E freighters we’re installing a special system that converts this waste heat into electrical energy. We’ve already fitted this system in other ships,” says Tigges.

As a result, hot exhaust gases from the engines won’t just be blown out into the air. Instead, they will be used to heat water to drive a steam turbine and a generator. The electricity produced by this system can be recovered onboard, rendering auxiliary diesel generators redundant. Thanks to this configuration, Triple E ships will generate up to 25 megawatt-hours (MWh) of energy per year. But electricity on ocean-going freighters isn’t needed only for the onboard electronics; it is also used for the freight itself, since many of the containers have to be refrigerated.

Siemens engineers have installed generators with motor functions on both drive shafts. These units will come into their own in situations where a ship uses less electricity than the generator produces. Under these circumstances, the extra electricity can be used to boost propulsion. Ideally, a total of up to six megawatts (MW) of additional power can be delivered to the two drive shafts while maintaining the same level of fuel consumption. Shaft generators with motor functions can also generate electricity. To accomplish this, the system switches from motor mode to generator mode, producing additional electricity from the movement of the drive shafts. This situation arises regularly in container ships. “It is often the case that the steam turbine can’t deliver enough energy to slake the refrigerated containers’ thirst for electricity,” says Tigges. “In warmer regions refrigeration can require between eight and eleven MW” – equivalent to the output of two big wind turbines. According to Tigges, the Siemens system reduces fuel consumption by over 12 percent, thus cutting greenhouse gas emissions. “For the route between Asia and Europe, the amount of CO₂ emitted by the super freighter per loaded container will be 50 percent below the average for the sector, thanks to the Siemens system,” says Tigges.

Ships That Learn. With a view to improving the energy balance of Maersk’s entire fleet, a Siemens digital efficiency manager will also be installed on the new ships. The system is already in operation on several ships. It evaluates information from up to 10,000 functions – for example assessing things such as the current fuel and energy consumption of the propulsion system. Data is also collected on the ship’s trim, the rudder position, and the weather. When necessary, these values are measured every second. “Our solution is an open system. As with smartphones, various suppliers can develop apps for this platform and make use of all the data in the system. For example, a program can suggest an optimal route based on the ship’s data and the weather, or it can suggest the best trim for current conditions,” says Tigges.

Data can also be transmitted to the shipping company via satellite, making efficient fleet planning possible. “Ships equipped with digital efficiency managers learn from one another. In addition, there’s competition among the captains, as the shipping company can see who is operating the most economically. When the system is optimally utilized, operating costs can be cut by another two to three percent,” Tigges adds.

Efficiency gains will pay off for shipping companies and could in themselves be important for the environment. In a study conducted in 2011, for instance, the International Maritime Organization (IMO) calculated that in 2007, carbon dioxide emissions from international maritime shipping amounted to 870 million tons. That’s more than the annual output of Germany and accounts for 2.7 percent of all worldwide emissions. Gains in efficiency are therefore urgently needed – even though, in terms of greenhouse gas emissions per metric ton-kilometer, shipping by sea is already the most environmentally friendly method for transporting goods over long distances. Maersk claims that only three grams of CO₂ emissions per kilometer will be produced for each ton of freight transported on the new container ships. By contrast, according to Maersk, a truck emits 47 grams of CO₂ per kilometer for each ton of freight it transports, and for aircraft the equivalent figure is 560 grams.