Triplee
Rendering of the Triple-E. Click to enlarge.

Mærsk Line has signed a contract with Korea’s Daewoo
Shipbuilding & Marine Engineering Co., Ltd. to build 10 of the
world’s largest and most efficient vessels—the Triple E (Economy of scale, Energy efficient and Environmentally improved)—with an option
for an additional 20 vessels. The newbuilds are scheduled for delivery between
2013 and 2015.

Four-hundred metres long, 59 meters wide and 73 meters high, the Triple-E is the largest vessel of any type on the water today, according to Mærsk. Its 18,000 TEU (twenty-foot container) capacity is 16% greater
(2,500 containers) than today’s largest container vessel, Emma
Mærsk. The Triple-E will produce 20% less CO2 per container moved
compared to Emma Mærsk and 50% less than the industry
average on the Asia-Europe trade lane.

In addition, it will consume approximately 35% less fuel per container than the 13,100
TEU vessels being delivered to other container shipping lines in
the next few years, also for Asia-Europe service.

Each vessel will cost US$190 million. Besides
its size, which provides superior economies of scale compared
to other vessels (more cargo means less CO2 per container
moved), the efficiency of Triple-E comes from its innovative
design.

The Triple-E vessels have a 26% slot cost advantage compared
to the 13,100 TEU vessels sailing on today’s oceans considering a full
roundtrip from Asia to Europe (based on a bunker price of US$600 per
metric tonnes). Slot cost is a consolidated figure from several costs; bunker fuel, vessel
costs (operational and capital) plus port and canal fees.

Two ‘ultra-long stroke’ engines turn two propellers, and specially
optimized hull and bow forms guide the vessel through the water
at the speeds typical in the industry today. An advanced waste
heat recovery system captures and reuses energy from the engines’
exhaust gas for extra propulsion with less fuel consumption.

To reduce the environmental impact of the vessels beyond
their lifecycle, Mærsk Line is setting a new standard for the way
vessels are recycled. All the materials used to build the Triple-E
class will be documented and mapped in the vessel’s ‘cradle-to-cradle
passport’. This means that when the vessel is retired from
service, this document will ensure that all materials can be reused,
recycled or disposed of in the safest, most efficient manner.

Propulsion system. The top speed of the Triple-E was capped at 23 knots,
two knots lower than Emma Mærsk’s top speed. This meant
a power requirement of 65-70 megawatts compared to
Emma’s 80 megawatts—about a 19% reduction. A slower max speed also enabled Mærsk Line to consider engines
that could operate at slower revolutions—‘ultra-long stroke’—
which provides the greatest fuel efficiency.

To retain the efficiency
created by the slower revolutions of an ultra-long stroke engine requires
a larger propeller diameter. However, the size of the propeller
is limited by the dimensions of the vessel and the available space
beneath the keel.

To mitigate these restrictions and achieve the desired efficiency,
Mærsk Line research determined that a two engine/two propeller
‘twin skeg’ system was superior to the one engine/propeller setup.
The Triple-E’s two propellers are 9.8 metres in diameter with 4
blades each, compared to Emma’s single propeller, which is 9.6
metres in diameter with 6 blades. The combined diameter of the
propellers provides greater pushing power in the water and the
fewer number of blades creates less resistance.

All together, the Triple-E’s twin-skeg propulsion system consumes
approximately 4% less energy than Emma Mærsk’s single
engine/single propeller propulsion system.

The MAN diesel engines weigh 910 metric tonnes each, and deliver output of 43,000 hp (32,065 kW). Fuel consumption is 168 grams bunker oil per kWh produced.

Waste heat recovery. The Triple-E is the latest in a succession of Mærsk Line vessels (20 vessels, including the 8 Emma Mærsk class vessels) to be equipped
with an energy saving advanced waste heat recovery system. For the Triple-E, the effect of the waste heat recovery system is a reduction in the engine’s fuel consumption and CO2 emissions by
approximately 9%.

When exhaust gas leaves the engine, it has a very high heat
potential. Utilizing this potential in an exhaust gas boiler, it is possible
to generate steam. The waste heat recovery system then supplies
the steam into a turbine connected to a generator which then
recovers electrical energy.