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Fuel savings ahoy

Fuel savings ahoy

An innovative diesel-electric hybrid propulsion system built around liquid-cooled variable speed drives means that the fuel consumption of the new MS Goblin dry cargo bulk carrier is 12.5% lower than that of its almost identical sister vessel, which has a conventional diesel-only propulsion system.

The MS Goblin is the latest acquisition of the dry cargo bulk carrier business owned by the Vranken family, which serves the inland waterways of the Rhine. To deal with the growing demand for the services offered by its business, the family ordered the new-build MS Goblin to operate as sister ship to its first vessel, the MS Lutin, which has been in operation since 2009.

However, like all ship owners, the family wanted to achieve the lowest possible operating costs, so they made the bold decision that the new vessel would be equipped with an innovative diesel-electric propulsion system instead of the traditional diesel propulsion system used on the MS Lutin. Their decision has proved its worth many times over.

Key elements of the propulsion installation on the MS Goblin are a 634kW main diesel generator, two 634kW diesel engines, each driving one of the ship’s two propellers, and two electric propulsion motors (E-motors) coupled to the propeller shafts. The E-motors are controlled by Vacon NXP liquid-cooled variable speed drives. This arrangement means that the propellers can be driven either by the diesel engines or by the electric motors.

In fact, the hybrid propulsion system used in the MS Goblin supports three operating modes: E-mode, diesel mode and diesel + E-mode. Optimum performance is achieved by selecting the mode that best matches the conditions of the voyage.

In the E-mode, Goblin runs without the main diesel engines, instead using power from the main generator set to drive the E-motors. The diesel engines and the reverse clutch are out of operation and only the thrust bearing of the reverse clutch is used in the E-mode. The E-mode provides comfort while sailing and the generator can run at a variable speed to reduce fuel consumption and reduce the acoustic noise level. In diesel mode, the Goblin runs on the diesel engines only, like a conventional vessel. Nevertheless, the E-motor rotates while sailing in diesel mode because it is coupled to the propeller shaft. The

E-motor therefore provides power to the on-board electrical system through an electronic grid generator, the Vacon MicroGrid. While sailing, the Vacon MicroGrid system always supplies pure 50Hz to the on-board electrical system. This means that the diesel generator set does not need to run whilst the ship operates in diesel mode.

The Goblin can also operate in combined diesel and

E-mode, when it uses all the available power for propulsion. The main engines run at a slightly higher speed and that part of the rotational speed gives the

E-motor an extra boost.

While sailing, the Goblin can switch seamlessly between the three modes of operation. Everything is programmed and approved by the ship classification society, to ensure that all operations function properly. Even at full?speed ahead or full speed astern (in an emergency situation) the vessel can switch between modes as required.

The captain and co-owner of the MS Goblin, Danny Pols, explains how the Vranken family quantified the benefits of the hybrid propulsion system: “My brother-in-law and I measured and compared the fuel consumption of the hybrid MS Goblin and the conventional MS Lutin on a round trip where the vessels were loaded equally load and travelled one after the other. The ships had exactly the same performance but the MS Goblin used 12.5% less fuel than the MS Lutin.

“Furthermore, the maintenance cost is €3000 per year lower on the MS Goblin due to the reduced running hours of the diesel engines. The maintenance cost includes spares and consumables, such as lubrication oil, filters and fuel injection nozzles.”

The propulsion systems for MS Goblin were supplied by Hybrid Ship Propulsion BV of Rotterdam. The company’s commercial director, Henri Kruisinga, commented further about the benefits of adopting the technology: “Initially, we focused only on river vessels,” he said, “but we also see a big opportunity for hybrid and electric propulsion on harbour tugs and ferries, where the potential for fuel savings can be as much as 20-25%. We are also starting to use the latest battery energy storage technologies to reduce the energy consumption further. Power peak shaving with batteries allows smaller diesel engines to be used and avoids inefficient modes of operation.”

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