Monday, 16 January 2012

Fuel consumption

Change of topic off the maritime catastrophe of the day. The Antipodean Mariner has been studying devices to reduce the fuel consumption on the Capesize vessels under construction. With heavy fuel oil north of $700 a tonne, bunker consumption on a Capesize bulk carrier is around $50,000 a day while steaming, compared with break-even operating costs of about $25,000 a day.

Capesize charter rates are much lower than this opex breakeven, presenting a 'perfect storm' scenario of low hire rates and high fuel costs. The economies of scale of large ships are astounding. A slow speed, turbocharged 2-stroke diesel main engine will move one tonne of iron ore one nautical mile on one gramme of heavy fuel. However, in the tonnages moved and quantities of bunkers consumed savings are investigated in every part of the process of turning bunkers into forward motion. It is a sad fact that the new IMO Tier 2 emissions standards requires engines to consume more fuel, and emit more CO2, than the Tier 1 standard in order to meet nitrogen and sulphur limits. The California-inspired obsession with smog controls has lead to this anomaly.

There are two main areas of focus for naval architects and engineers when aproaching bluff, high block co-efficient bulk carriers and tankers. The first is the bow area, and the reduction of the wave form. Bulbous bows are falling out of fashion - great for fine-lined container and passenger ships but not for hulls experiencing up to 13 metres difference in draft between laden and ballast condition. The straight stem bow with the hint of a bulb is returning to a shipyard near you.

The second area is flow around the propellor. A number of proprietary systems make claims of 5-9% reduction in power requirements through harnessing the forward motion of the ship to improve flow into or behind the propellor. Even 5% translates to 3.5 tonnes, or $2,500 a day in operating costs.

Unfortunately, many of the Capesize ordered and built as a consequence of the 2007 freight rates orgy have little or no thought put into fuel economy.  The Japanese Yards, with Government R&D assistance, have achieved some spectacular success in recovering energy and reapplying to power the ship on daily consumptions of ships half their deadweight.

Some pictures of hot technology in the market - an Oshima Seaworthy Bow on a forest products carrier, MOL's finned propeller boss and Becker's Mewis Duct.

The Antipodean Mariner


  1. Very thought provoking post. I don't think many landsmen think about the cost of bunkers.

  2. Heh...yet another reason to recover heavy fuel oil from wrecked ships before it goes in the ocean...that stuff is black gold.

  3. Can ONE gram of bunker move one tonne on one NM ? It's nearly incredible...would be good to see some calculations.
    Thanks for your posts.

  4. Here's the maths. A 205,000 DWT Cape burns about 69 tonnes of heavy fuel oil to make 14 knots laden. HFO has a density of about 1.0 for these purposes. So 69,000 litres of HFO per day is 2,875 litres per hour, 205 litres per nautical mile. 205 litres/kg consumed to move 202,000 tonnes of iron ore (plus 25,000 tonnes of ship and 3,000 tonnes of bunkers and stores) one Nm. Accepted that this does not include the ballast leg from disport to loadport but the economies of scale of ocean freight compared to any other form of transport are pretty compelling.

    Glad you enjoy theblog, AM

  5. Thank you for your answer, indeed the economies are great but the sulphur oxides are still high so it sadly more polluting from this point of view.
    I enjoy the blog since I heard that a blog about Rena has been closed down and I discovered yours.
    But I still have one question about Rena, what is this command post on the port wing looking out of the water?

  6. Rena was fitted with a conning station on each bridge wing, common on container ships, ro-ro's and ferries. The conning station has bow thruster, main engine and sometimes helm controls to enable the Master and Pilot to control the docking from the wing so they can see the ship coming alongside.


  7. Hmm, very interesting, never heard of it, Thanks.

  8. And what about of fuel consumption of MDO, during the staying in port under argo-handling operations, and passage channels?

  9. I would like to estimate fuel consumption for a paper I am working on. Say, for example, I want to calculate fuel consumption on a 50,000 DWT ship with a transit time of 24 days. The product weighs 45 pounds per cubic foot. First, how much product can I get on the ship. Second, how much fuel will the transit take? I am looking for an average expectation, not a specific case. Can I get any help?