AWT Weather Routing/Routeing: Applied Weather Technology

Slow Steaming and Optimal Routing: Question and Answer Interview with George Schlinkert, Vice President of Operations at AWT

Q: A recent study suggests the shipping industry could cut carbon emissions by up to 33 percent by slow steaming. How does AWT help its customers to slow steam?

A: At AWT, we encourage our customers to slow steam as often as is safely possible. Many factors for each voyage are considered, such as the track sailed, weather, draft, trim and even different hull coatings on different ships. Given these considerations, we suggest the optimal route to help ensure safety and fuel efficiency. Slow steaming, when combined with the optimal route, provides the best possible scenario to reduce fuel consumption, curb carbon emissions and ensure safety.

Without the optimal route, slow-steaming ships may be exposed to unsafe conditions. In stormy weather conditions, slow steaming can prolong a ship's exposure to heavy seas. Slow steaming may also have unforeseen effects on ships in relation to storms. For example, slow steaming may allow for a storm to move away from a ship before she encounters it; however, it may have the opposite effect and reduce the ship's ability to avoid the stormy weather. Combining the optimal route with slow steaming helps to ensure safe and fuel-efficient sailing.

Q: Is AWT seeing an increase in customers who are slow steaming?

A: Slow steaming has been a steady practice for quite some time now. What we are seeing are questions with regards to how to best implement it, and whether all ships within a fleet are sailing equally efficiently. AWT is assisting our clients in determining answers to this complicated question which has many factors affecting each voyage, including track sailed, weather, draft, trim, and different hull coatings on different ships.

Q: Currently how do AWT's voyage optimization experts meet the needs of customers who are interested in slow steaming? How does slow steaming differ from the practice of constant RPMs?

A: Regardless of ship speed, the proper route can save five to ten percent of fuel for trans-oceanic voyages. When advised that slow steaming is required, AWT can obtain the required speed or ETA from the Captain or ship operator. Advice can be given to the ship Captain or operator regarding the required speed setting to achieve the required arrival.

This, of course, differs from a constant RPM setting which forces a ship to supply extra horsepower when encountering heavy weather. To maintain the RPM at a time when the ship is least efficient with the highest slip will result in burning additional fuel.

A ship Captain has two options for reducing ship motions in heavy weather. Change the course or change the speed. By maintaining a constant RPM, one of those two options is removed and the Captain is left with only one option; adjust the course which would add additional mileage, lengthen the voyage and burn excessive fuel.

Q: Can you describe a situation where you helped a Captain to slow steam by providing the optimal route?

A: A voyage that minimizes fuel consumption, fuel costs and related carbon emissions consists of two main components – speed and course. A ship traveling at a speed that is ideal for minimizing fuel consumption, but that is not following the optimal route, will consume more fuel than a ship that is traveling both at the optimal speed and along the optimal route.

When crossing the Pacific, the shortest distance will take a ship near or in some cases north of the Aleutian Islands. Indeed, this is often the optimal solution. However, any mariner knows that the shortest route is not always the best route. The following example, pictured below, shows the route recommended by AWT and followed by the Captain on a recent voyage.

Access to the shortest route was blocked by a severe storm in the Gulf of Alaska that generated 11 meter waves to the north. AWT's routing experts recommended the Captain to take a longer route that traveled south of the heavy wave region. By doing so and averting heavy weather, the Captain was able to sail at an optimal slow speed, and reduce fuel consumption by about 45 metric tons (MT).

Economical speed steaming is clearly documented to reduce fuel consumption; however, it only safe and beneficial when tied in with proper voyage optimization services.

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