## Fuel economy of the world's longest in-service ship

The Emma Maersk is the second longest ship in the world, and the longest currently in service. It's so large, it looks photoshopped into any picture it appears. Driving such a large ship requires a lot of power. From Wikipedia:

We started talking about energy consumption after watching a practice version of Saul's upcoming E-Tech Keynote, Energy Literacy, and Dave Culp of Kiteship and Speed Sailing did a back-of-the-envelope MPG calculation for this ship:

Dave concludes:

Images from jtashipphoto.dk and Wikipedia.

*The Emma Maersk is powered by a Wartsila-Sulzer 14RTFLEX96-C engine, currently the world's largest single diesel unit, weighing 2,300 tons and capable of 109,000 horsepower (82 MW). The ship has several features to protect the environment. This includes recycling the exhaust, mixed with fresh air, back into the engine for reuse. This not only increases efficiency by as much as 12% but also reduces engine emissions. Instead of biocides, used by much of the industry to keep barnacles off of the hull, a special silicone-based paint is used. This increases the ship's efficiency by reducing drag while also protecting the ocean from biocides that may leak. The silicone paint covering the part of the hull below the waterline is credited for lowering the water drag enough to save 1200 tons of fuel per year.*We started talking about energy consumption after watching a practice version of Saul's upcoming E-Tech Keynote, Energy Literacy, and Dave Culp of Kiteship and Speed Sailing did a back-of-the-envelope MPG calculation for this ship:

*A few more facts about Emma Maersk:**Running at her rated 80 Mw, her main engines burn 14 tons of residual fuel each hour. Annually, that's 97,400 tons of fuel. Her auxiliaries, delivering their full 30 Mw, burn an additional 6.6 tons/hour, for a total fuel burn of 20.6 tons/hour. Given 290 steaming days/year (80% capacity factor, which is conservative), this yields a total annual usage of 143,400 tons or about $64.5 million in annual fuel costs.**Burning 20.6 tons/hour = 6724 gals/hour. At 31 kts/hour, this equals .0046 nautical miles/gallon. At 6076 ft/nautical mile, that's 28 feet/gallon of fuel burned.**The 1200 tons saved by her "revolutionary" bottom paint represents a bit less than 1% of this cost, so increases her fuel mileage to 28.2 feet/gallon.*Dave concludes:

*You gotta haul a lot of containers full of $7 tee shirts to make this profitable.***28 feet/gallon!**Images from jtashipphoto.dk and Wikipedia.

is 115000 btu/gal which is 121 MJ/gal. Diesel has slightly higher energy content,

maybe 125-130 kbtu/gal.

To put this in perspective, even the best batteries have pitiful mass and volumetric energy densities, which is why electric cars are so handicapped now. We need

big energy developments before the electric cars will be really competitive.

http://en.wikipedia.org/wiki/File:Energy_density.svg

Forum Topic, i.e. "a blag" and in the right place. (It's also >2 years old).L

I find it interesting though, so I was pleased you "bumped" it.

L

Drag power goes as the cube of speed and as a result mileage goes as the square of speed. 31

^{2/25}2 = ~1.5.In other words, you fudged the fuel economy by a factor of two!

And you didn't actually touch the question of efficiency, you just handwaved it away with a silly comment about t-shirts. She has a DWT of 157 000 metric tonnes, almost all of which is containers filled with goods. The ratio of goods to goods+container is close to 90% in the ideal case and closer to 70-80% real world.

If you do the calculations you get about 80 J/(kg*km), about 2-3 times as efficient as rail and 5-10 times as efficient as trucks. That's monstrously efficient, it takes 0.05 gallons(~20 US cents) to ship a 5 kg bag of rice(~11 lb) half-way around the world(that's probably less oil than it takes to produce the thick plastic bags rice usually comes in). It takes less energy to move 1 lb one US mile than you consume while you sleep during 1 second.

^{2/25}2 = ~1.5."That did not come out right at all, let me try again 31

^{2}/25^{2}huge!