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Since Midsummer, commuters and tourists in part of the Stockholm Archipelago may have noticed how quiet and clean one of their usual ferries is. The difference is striking compared with the normal clank and grind and diesel smells of the many boats that ply this beautiful area in and around the Swedish capital.

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That’s because the M/S Silverö ferry, which sails between the Vaxholm and other nearby islands, has been retrofitted with a fully electric ���ϲ����� e-machine.

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The pioneering passenger boat is the latest exciting example of the longstanding and highly productive partnership between ���ϲ����� as engine maker and Blidösundsbolaget, the largest ferry operator in the Stockholm region.

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“Over the years we have built up a close cooperation with ���ϲ����� as our provider of diesel engines and selective catalytic reduction systems for our boats,” says Fredrik Liw, Blidösundsbolaget’s Technical Superintendent. “In 2018, our M/S Rex ferry was fitted with a ���ϲ����� hybrid electric engine and that has been a success.”

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“So, 18 months ago, when the time was right for considering full electrification, we asked ���ϲ����� to work with us on fitting an e-machine so we could test it under real working conditions.”

The M/S Silverö ferry was identified as the ideal candidate for the retrofit of a 330kW prototype e-machine already in use for trucks. Even though the boat was built as far back as 1970, she has remained a steadfast member of the company’s fleet, and her strong hull and overall structure are still in great condition.

It also helps that the e-machine weighs just��400 kilos, less than a third of that of a diesel-engine equivalent, with a much smaller footprint too. Its four gears means perfect propeller matching, and the twin installation allows counter-rotating propellers for efficiency without heavy marine transmissions.

In fact, the main challenge since then has not been the operation but the charging infrastructure for the batteries powering the vessel, which led to temporary solutions for a couple of weeks.

Blidösundsbolaget’s electrical partner Marinelektro has since established a permanent charging solution next to the ferry’s mooring point. Up to 450 KW of power can be stored there, and the vessel, which has a capacity of 780 kilowatt hours, can be charged with 400 KW at a time. The charging takes place at night or during breaks during the ferry’s daily schedule.