August 13, 2022

Three feet above the waves, the Candela P-12 sprints across Lake Mälaren near Stockholm, Sweden. With only its hydrofoils cutting through the water, the boat leaves virtually no wake, noise, or emissions—a sea change from the hulking diesel-powered ferries that currently haul commuters through the archipelago that makes up the Swedish capital.

So far, it’s a water-bound fantasy: While Swedish startup Candela is already manufacturing leisure versions of its electric flying boats, the P-12 hasn’t yet been built. Candela CEO Gustav Hasselskog says the boat is in the “design for manufacturing stage” ahead of a November launch that will be followed by a trial next year. The aim is to have the flying ferry form a part of Stockholm’s public transport fleet.

Cutting carbon emissions from ferries is a priority for a city surrounded by water. The city’s existing fleet of 60 ferries emits 40,000 tons of carbon dioxide annually, making up 8 percent of total shipping emissions in Sweden—and they’re spewing that air pollution in cities, raising public health concerns. “Shipping has to stop using fossil fuel, fast,” says Simon Bullock, a researcher at the University of Manchester’s Tyndall Centre for Climate Change Research. “For short journeys, electric ships can be a big part of the solution.”

On that point Sweden is ahead of the curve, with Stockholm working toward emissions-free ferries by 2025. Electric ferries have previously been trialed in the Swedish capital, with local authorities testing another model from Green City Ferries alongside the flying P-12. Norway uses electric passenger ferries to tour its fjords, Belfast in Northern Ireland is trialing a similar “flying” style boat, and a project at the University of Plymouth in the UK is converting diesel ferries to electric. That’s good news given that ferries, most of which are powered by diesel, are a major environmental headache: EU data shows ferries represent 3 percent of all vessels but make up 10 percent of carbon emissions, while more than 95 percent of US ferries are powered by diesel.

But Candela believes there’s more to cleaning up Stockholm’s commuter traffic than emissions-free energy: making ferries quick enough to persuade more people to ditch cars. Traveling from the suburb of Tappström to central Stockholm takes 50 minutes by car during rush hour, but the P-12, which can hit 30 mph, could navigate the waterways between the two in 25 minutes, Hasselskog says. Waxholmsbolaget, the agency that runs public transport boats in the archipelago, carries 1.2 million passengers annually, but that’s compared to 780,000 commuting trips by other forms of public transport each day in the city—in short, there’s room to get more Swedes in the sea.

The problem with powering any form of transport with electricity is it requires heavy batteries. That’s a particular problem for boats, as they suffer drag in the water. To address this Candela uses hydrofoils, legs that extend down into the water and act like wings, propelling the boat up into the air as it picks up speed like an aircraft during takeoff. “In harbor the foils are fully retracted, so they’re protected,” Hasselskog says. “But then you lower the foils and hit the throttle and off it goes. The control system takes care of the entire takeoff sequence, it’s like an airplane.”

Hydrofoil boats aren’t new, but electric power and automated controls are. The carbon-fiber Candela P-12 will have twin propulsion systems powered by 180-kWh batteries, letting it run three hours before requiring charging. At 12 meters in length and 4.5 meters across, the 8.5 metric ton boat will carry 30 seated passengers.

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