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:

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 and Wikipedia.

Picture of Fuel economy of the world's longest in-service ship
geeklord6 years ago
If this makes any sense at all, what is the potential energy of a galon of gasoline in watts(or another sort of measurement,joules?).
good question---as you say, the energy is measured in joules not in watts, which are a unit of power (energy per unit time). A typical figure quoted around
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.
Funny, I just finished Science 9 in school (with a 99% percent, thank you very much), and I learned all about joules, watts, Newtons, etc. That's a lot of energy. I now see why burning things is so easy.
All you had to do was go to Wikipedia and type "gasoline energy content". First hit.
neffk4 years ago
This isn't really an instructable.  Don't you have a blag where you can post stuff like this?  Or maybe you should add it to Wikipedia.  It's interesting and all, but not the kind of thing I expect on this site.
lemonie neffk4 years ago
No, it's a Forum Topic, i.e. "a blag" and in the right place. (It's also >2 years old).

neffk lemonie4 years ago
lemonie neffk4 years ago
I find it interesting though, so I was pleased you "bumped" it.

scubascooby5 years ago
I wonder if a few sails might save them even more fuel ? I remember Cousteau (Halcyon) and then Shell experimenting with rigid vertical aerofoils to power ships in the 80's.
My God, what hath man wrought?
ring's for you, Dr. Bell
thawombat6 years ago
love this ship. you cant imagine how big it is untill you stand on one. i was so lucky to get a tour of one of her sister ships. :)
Oddly though some of the later steam powered boats were capable of similar fuel efficiency... I always did wonder why it fell out of fashion for boats, a big steam turbine boat running on coal could potentially be cheaper, considering fuel costs of coal vs. oil...
though coal being a solid would be much harder to handle, and the engines would be more like that in a coal power station then a traditional steam engine. it would just be too much hassle for what its worth i believe. oil you can just pump in and have standard, big fat diesel engines.
Steam turbine ships are far from out of fashion. China and korea the main ship building nations are biulding gas carriers with steam turbines all the time. But fueled by coal? No. They use the gas they carry and burn that in the boilers. These ships still carry HFO, heavy fuel oil (the black sticky stuff) mostly for the ballast voyages if they are short on gas and they burn that in the same boilers. The equipment needed to supply coal to a boiler is just too high maintenance. There is also the safety risk of carrying coal. Most container ships, gas and oil carriers etc do run on heavy fuel oil for their main engines but there are alot which run there aux generators (which supply electric power for the ship)on gas oil or diesel oil which is very close to what you put in your diesel powered car you go to the shops in. That costs a bit more than the black sticky stuff. And also there are new generations of large gas carriers coming out which are powered by duel fuel engines running on gas and diesel oil. These are great while running on gas which is technically free as it would of got vented off if it wasn't used. When they do run on diesel oil they drink the stuff. These are big 4 stroke engines, usually 4 on a ship rated at between 8000kw and 14000kw. But all these large ships now have to change over from HFO the black sticky stuff to gas oil or diesel oil when entering USA waters and large ports in Europe so what comes out the funnel is alot cleaner. Thats got to cost a bit. But they wouldn't do any of this if they weren't making money!!!!!!!!! and they make alot of it!!!
Soylent6 years ago
Her quoted service speed is 25 kts; it was chosen because the engine is not operating at maximum efficiency when it is running at maximum power and as a trade off between speed and fuel economy. From your quoted fuel consumption numbers it operates at 35% of maximum efficiency instead of the >50% it is capable of.

Drag power goes as the cube of speed and as a result mileage goes as the square of speed. 312/252 = ~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.
Huge diesels like this can get more than 50% efficiency, vs. 30% for a truck engine. That's just one piece of how it works out to be an efficient way to move freight, but an interesting one.
Soylent Soylent6 years ago
"Drag power goes as the cube of speed and as a result mileage goes as the square of speed 312/252 = ~1.5."

That did not come out right at all, let me try again 312/252
FireBAT6 years ago
It's the same as saving money by buying bulk goods- less packaging per ounce of product equals a lower cost. A single "intermodal" train can carry hundreds of trucks worth of containers. One of these ships can carry hundreds of TRAINS worth.
trebuchet037 years ago
That's a pretty cool calculation.... It should be noted, that while the number sounds atrocious - it's way more efficient than cars/trucks on the road today. Plus plenty of room for improvement :)
Brennn107 years ago
Wow. That is not something I would want to get stuck in a channel with. That ship is huge!
Goodhart7 years ago
Thank goodness that isn't "rowed"
Kiteman7 years ago
Good grief. Imagine having to stoke the equivalent in coal-fired boilers...
Wyle_E7 years ago
That's "knots", not "knots per hour." A knot is a nautical mile per hour; kts/hr would be a unit of (rather slow) acceleration. It's worth noting that the "residual oil" that these huge diesel engines burn is the gunk that's left in the bottom of the still after all of the more valuable hydrocarbons have boiled off. About the only other use for that stuff is making asphalt pavement, so these ships aren't competing with anything else for fuel.
CameronSS7 years ago
It's interesting, though...I read an article about a much smaller cargo ship and its fuel economy and shipping capacity, calculated it out, and found that the ship was the equivalent of 2500 fully loaded semi trucks, each getting 25.5 mpg. Not really that bad.
LinuxH4x0r7 years ago
Amazing and disgusting at the same time