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A joint development project (JDP) between DNV GL, Statoil and Farstad Shipping is said to have demonstrated that offshore supply vessels (OSV) can save up to 21,000 euros on their annual fuel bill, by running the vessel at optimal trim.

The project partners carried out a comparative study in the North Sea to document potential energy savings created by using DNV GL's trim optimization tool, ECO Assistant, on a platform supply vessel (PSV).

"Even if our modern PSVs are highly fuel efficient due to advanced hull designs as well as innovative engine- and propeller configurations, it is interesting to observe how much impact operational considerations such as trim optimization has on the energy consumption," remarked Borge Nakken, Vice President - Technology & Development, Farstad Shipping Norway.

"As a charterer of vessels we work continuously to reduce the environmental footprint of our chartered in fleet. We welcome initiatives taken by the ship operator to reduce the fuel consumption as part of daily operation," said Frida Eklof Monstad, Manager for Marine in Statoil's unit for logistics and emergency response.

"Because of its bow design and relatively flat transom stern this PSV design proved to be sensitive to changes in trim. We were excited to see the results demonstrated that trim optimization can help a modern PSV save significant amounts of fuel, without affecting its normal operation," explained Petter Andersen, Principal Consultant for Fleet Performance Management at DNV GL - Maritime.

The pilot vessel Far Sun and its sister ship Far Sygna took part in the study. Owned by Farstad and chartered by Statoil, both vessels had the same operational profile and were in service off the south west coast of Norway. Over the study period, which ran for approximately six months, Far Sun used DNV GL's ECO Assistant.

On both vessels, an automated onboard data collection system gathered information about the required power, trim and fuel consumption. This was sent to DNV GL and analysed using the ECO Insight performance management solution.

According to DNV GL, the results revealed that by using ECO Assistant, Far Sun consumed an average of 4.3 percent less fuel than Far Sygna when operating between 4 and 14 knots. The greatest savings (over 5 percent) were achieved when the vessel was operating at speeds over 7 knots.

ECO Assistant contains a trim-power model, which is based on ship data and drawings that incorporates seven speeds, seven drafts and seven trim conditions. The optimum trim, related fuel savings and other hydrodynamic results are presented in a digital interface. The trim model also includes speed-power and fuel oil consumption (FOC) curves for the full speed range of the vessel, enabling accurate predictions of additional fuel consumption due to extra cargo or ballast.

Today, more than 750 vessels worldwide are using ECO Assistant for trim optimization.