Triple E, the world’s largest container vessel does not require a gas guzzling monster in its engine room to move it through the water. In fact, the Triple-E’s ‘twin skeg’ propulsion system (two-engine, two-propeller) is central to the vessel’s world record efficiency.
Maersk Line has placed an order with Korea’s Daewoo Shipbuilding & Marine Engineering Co., Ltd to build 20 Triple E vessels. The first 10 vessels will be delivered 2013 and 2014 and the remaining 10 vessels are scheduled for delivery in 2014 and 2015.
To build the world’s largest and most efficient vessel, Maersk Line needed to custom design a propulsion system that would be both powerful enough to move the vessel, but with maximum efficiency to be worthy of the Es in its name: Economies of scale, Energy efficient and Environmentally improved.
For starters, 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 only 65-70 megawatts compared to Emma’s 80 megawatts – a 19 percent reduction.
A slower max speed also enabled Maersk 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 re¬quires 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, Maersk 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 percent less energy than Emma Mærsk’s single engine/single propeller propulsion system.