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#1 - Green Vessels

Less Haste Makes Less Waste

There are many commercial options for shipowners to make their fleet more environmentally friendly and to meet new regulations.  One option on the market is for shipowners to slow down: Opting for slow steaming can cut both fuel costs and emissions.

Over recent years the shipping industry has been hit by environmental regulations that will see shipowners having to ‘green up’ their fleets to meet the new standards.

Reducing CO2 Emissions

Courtesy of DNV.GL

Courtesy of DNV.GL

Jan-Olaf Probst, head of business development at DNV GL explains that  slow steaming stemmed from the Kyoto Protocol, where it was put to the industry that shipping needed to reduce its CO2 emissions. This was then handed to the IMO to come up with an industry standard that could be applied to shipping, which has led to the energy efficiency design index (EEDI) standard that is now being applied.

Slow steaming presents an option for owners with older vessels that haven’t been designed to EEDI standards, and could save money. “The largest driver for cutting CO2 emissions for an existing vessel is to drive slower,” Probst says. DNV GL has highlighted that newbuilds have adopted the EEDI in their designs, with a trend towards shorter and wider ships.

New Panamax Vessels

Probst adds that the concept to design and build wider vessels is most prevalent with containerships, since the width will be always enlarged by steps of 2.52m due to the size of a container box. If, for example, the present Panamax class (about 5,000 TEU) with a beam of 32.2m is widened to 37.25m then the stability of the ship will be beneficially influenced. There are even plans to build New Panamax container vessels (about 12,000 TEU), based on the new lock dimensions, with up to 55m in beam.

Probst adds  that “the ‘new’ 5,000 TEU designs had been the so-called baby-Panamax vessel with a beam of 37.2m. All these designs come with a maximum speed of 22.5 knots or slightly slower.”

Slower Rotating Speed


Courtesy of GNV DL

Having a vessel that operates at a slower speed also opens options for propulsion. Probst notes that vessels that operate at a slower speed do not require larger engines, and can have one or two fewer cylinders. DNV.GL says that the main engines built eight to 10 years ago had mostly rotating speeds of 120-135rpm. Nowadays, long-stroke main engines operate at around 80rpm.

The slower rotating speed of the main engine leads to an enhanced propeller efficiency and therefore reduces the fuel oil consumption compared to a main engine/propeller design.

Probst explains that: “A propulsion system will always be designed for the maximum load. However, long-stroke main engines have the benefit that the specific fuel oil consumption is quite equal over a large part of the main engine load. This means that the fuel oil consumption is relatively constant-e.g., over a load of 45% to 75% of the main engines.”

Retrofit Modifications

Engine manufacturers such as MAN Diesel have been looking into what options it can offer shipowners in its own product lines. The company says that low load (slow steaming) operation down to 10% to -20% MCR is possible with the MAN B&W engines and there is an increasing trend to operate in these very low engine load ranges. As the engines were not designed for this operational profile, various retrofit modifications to the engine can compensate.

Peter Dan Petersen, head of marketing and documentation, MAN highlights:

Slow steaming has led us to develop existing engines that were originally designed for higher loads to bring them down to operate at lower loads.

He also adds that all the container operators that MAN co-operate with have opted for slow steaming and have been optimising their vessels for this.

Further upgrades that are available and will also enable other reductions in fuel and lubricating oil are measures such as; turbocharger cut out, slide fuel valves and Alpha lubricator upgrades.


However, having a vessel designed for the benefits of slow steaming and operating a planned slow steaming schedule still seem to be a ways off, according to DNV GL. The EEDI Tier III came into force on January 1 of this year, but as that currently only effects U.S. waters because of its Emission Control Area (ECA), further development is yet to be seen.

Probst says that it is expected that China will come up with an ECA area, which will push the regulation for compliance further for many.

Keeping Costs Down ?

Another conundrum that Probst foresees is the cleaning of exhaust gas, for which they will need to burn more oil. Oskar Levander, vice president of innovation at Rolls-Royce, comments that this is a good time for ships to be burning more fuel while the fuel cost is down, so they can go faster.

But in the current financial climate, owners and operators are looking at options that keep costs down. Probst reiterates the savings that can be made by slow steaming, saying that: “With a speed reduction of only 2 knots, the amount of vessels ‘arrived in time’ has improved and has seen an immediate impact on schedules.”

About the Author

Samantha Fisk worked at RINA (The Royal Institution of Naval Architects) for 7 years and has now gone into freelance, working for European magazines.

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