McKay’s marine and engineering divisions delivered the first fully electric passenger ferry in the Southern Hemisphere - the Ika Rere.
The Ika Rere is a 28 tonne, 19m, carbon fibre, twin-hull fully electric ferry capable of carrying 132 passengers at 20 knots. The vessel is powered by an independently supplied 325kW liquid cooled electric AC motor in each hull. Two banks of Lithium-Ion liquid-cooled batteries totalling 5500kg and providing 550kWh of installed capacity are used to drive the two motors.
Propulsion and Energy Storage
Propulsion of the vessel is controlled by an integrated Danfoss Editron system, comprising two Danfoss EM-PMI1540-T200 motors rated to 325kW, driven by two Danfoss EC-C1200-450 DC-AC converters. Each motor is supplied from its own 750Vdc bus with has its own set of charging plugs, and this provides the redundancy required of maritime vessels. Each 750Vdc bus is in turn is fed by three Danfoss EC-C1200-450 converters in DC-DC mode, and each convertor is supplied by two strings of six XALT XMP76P battery packs. A total of 72 XMP76P battery packs are installed, and upgrading the XALT XMP76P battery packs to the XALT XMP98P battery packs would provide a 29% increase in capacity and range of the numbers contained herein.
Control of the Vessel: The VCAM
Control of the Ika Rere is through industry standard SIMRAD propulsion levers and two touch-sensitive graphical displays – the VCAM – used for monitoring and control of the vessel. Communications between the various subsystem of the vessel are undertaken using CAN bus and other commercially available communication protocols.
The VCAM GUI system will communicate vessel parameters such as vessel power and performance, notifications, speeds and range, temperatures, and pressures.
The power and battery states for each independent hull are graphical presented to the vessel operator, along with a checklist for the operator to follow when starting and stopping the vessel.
Operational Range
The operational range of the vessel is dependent upon sea conditions, battery age, and the speed of travel. A return trip at 20 knots between Queens Wharf and Days Bay with the maximum passenger load consumes 310kWh, and the two 325kW motors would deplete the batteries to their safe operating level point in 42 minutes.
A calculation of the operational range of the vessel is presented to the master via the VCAM, as shown in the VCAM GUI Propulsion Overview. The range presented is a calculation based on current battery state of charge, current vessel usage, and the current passenger load entered by the master, and therefore takes into account current maritime conditions.
