Environment and Sustainability, Latest Contracts, Operations & Maintenance

Electric propulsion system for rail-enabled ferries

KiwiRail has selected Siemens Energy to supply the integrated Electric Propulsion System (EPS) for Interislander’s new rail-enabled, more environmentally-friendly ferries.

The EPS includes the alternators, switchboards, batteries, azimuth thrusters, power and battery management systems and integrated alarm system. In addition, Hyundai Mipo Dockyard and Siemens Energy entered into a contract to design, supply, install, and commission the EPS for the two new Interislander ferries.

The Interisland Resilience Connection (iReX) project is a $1.45 billion investment which will see two new, rail-enabled ferries coming into service in 2025 and 2026. The project also includes modernised ferry precincts in Waitohi Picton and Kaiwharawhara in Wellington, including ferry berths, terminals and both rail and road connections.

Selecting Siemens Energy as the maker for the EPS is another step towards the 40 per cent reduction in emissions that the new fleet will bring to Interislander operations and KiwiRail’s goal of net-zero carbon emissions by 2050.

iReX Ships Programme Manager Massimo Soprano said the Siemens Energy system selected will deliver performance improvements in safety, manoeuvrability as well as in reducing environmental impact for the Interislander operations.

The hybrid technology selected to drive the new ferries will use electrical propulsion from generators fuelled by diesel and batteries recharged by electrical shore power.

Batteries will power 30 per cent of the three-hour journey. Under normal conditions the ferries will be operating on batteries only while manoeuvring and in port, using a combination of battery and shore power. Any surplus energy produced by the generators during sailing can also be battery stored.

The selected propulsion system uses ‘pods’, which are mounted outside the hull of the vessel, and contain an electric motor which drives the external propellor. The pods can rotate through 360 degrees independently or working together providing greater manoeuvrability, particularly during berthing, and greater fuel efficiency, compared to the current ferries which use a conventional shaft line/twin propellors to drive the ships.

Podded propulsion can deliver power to any direction, which enables a much higher level of control in prevailing conditions. They are quieter under water and create little or no vibrations. The pods are powered by electricity and the combination of diesel generators and hybrid battery systems means operators have more control over consumption, power supply options, redundancy, and resilience.

Other significant makers selections by KiwiRail to date include the selection of Kawasaki Heavy Industries of Japan to supply four 2800 Kw bow thrusters for each of the new ferries and Mitsubishi Heavy Industries of Japan to supply fin stabilisers.