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The oldest operating ferry in Finland, the Fori, is due to become the country's first all-electric passenger vessel after undergoing a retrofit.

The city of Turku is scheduled to relaunch the historic ferry on Saturday, April 29, complete with a new zero-emission electric drivetrain to deliver greater efficiency, less noise and reduced operating costs.

The Fori initially entered service in 1904 after the City of Turku commissioned local shipyards Aktiebolaget Vulcan to build a city commuter ferry to take passengers across the Aura River to Abo.

Since then, the distinctive little orange boat - named after the Swedish word for ferry, 'farja' - has traversed its route back and forth across the river for more than a century to become a transport icon for the city.

During the retrofit, the boat's diesel-powered hydraulic motor and the old control system was removed. The new installed system was eight tons lighter, consisting of two permanent magnet motor drives and two DC/DC converters which control the ferry's DC grid.

The new vessel draws power from batteries that are charged overnight, with the new power system simultaneously improving redundancy and making it possible to run on one or two motors - particularly important during icy conditions. This also allows future motor maintenance to be done in shifts, with no interruption to vessel operation.

The DC/DC converters serve to increase the battery voltage to a level that is more suitable for the motor drives. This minimises losses while maximising performance and reliability.