Flying foil ferries for the climate win


Flying foiling ferries: a fantasy or the fast-track to a fossil-fuel-free future?


Stockholm could become a world leader in green public transport, not by plane, not by train, but by flying ferries.


Everyday 4,500 passengers take to ferries to travel between the Stockholm archipelago. In a city surrounded by water where water transport ironically goes underused, lowering commuter traffic on the roads and curbing carbon emissions from ferries is a top priority.


The city’s existing fleet of 60 ferries emits 40,000 tons of carbon dioxide annually, making up 8 percent of the country’s total shipping emissions. And while Waxholmsbolaget, the agency that runs public transport boats in the archipelago, carries 1.2 million passengers annually, that number pales in comparison to the 780,000 commuting trips by other forms of public transport each day in the city.


Getting Swedes to the sea and making it green could solve two problems at once. The Swedish startup, Candela, might be riding the waves of a solution.

The Candela P-12 is a hydrofoil ferry. This means that its hull lifts above the water, propelling it across the sea at an increased speed. It flies across the Baltic, three feet above the waves, leaving little to no wake, noise, or emissions. Right now, the Candela P-12 is a fantasy. The startup, which already makes leisure electric boats, is still in the manufacturing stage of the P-12, ahead of a November launch that will be followed by a trial next year. Candela’s goal is to have the flying ferry form a part of Stockholm’s public transport fleet.


The P-12 is a foil to current Swedish diesel-powered ferries, and as reported by Wired, is the latest in a wave of electric boats to make their way to Sweden. The country is ahead of the curve, with Stockholm working towards emissions-free ferries by 2025. One emission-free ferry that the capital has tested is Green City Ferries Movitz. The 75-foot ferry, which carries 100 passengers, was trialed by local authorities last year, alongside the P-12.


The difference between the P-12 and existing electric boats, the company says is the P-12’s speed. Candela believes it is key in convincing people to ditch cars. For the everyday person, traveling from the suburb of Tappström to central Stockholm for work takes 50 minutes by car during rush hour. But flying at 30 mph, the P-12 can navigate the waterways from the suburb to the city in 25 minutes, Candela CEO Gustav Hasselskog told Wired.


The other difference between the P-12 and other electric boats is the battery. Usually using batteries in anything electric is heavy, which in the case of ferries, weighs down the boat. To address this problem, Candela uses hydrofoils: legs that extend down into the water and act like wings. It propels the boat into the air, picking up speed much like an aircraft during takeoff. The engineering makes Candela the “fastest electric ferry in the world” according to Bloomberg.


Equipping boats with hydrofoils isn’t new, but Candela’s electric power and automated controls are. As Wired reports, 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. While the P-12 seats less passengers than its competitor Green City Ferries, Hasselskog argues that a large fleet of smaller boats offers more flexibility than larger ferries and could mean they’re used on demand.


Once built, the P-12 is also poised to use less energy than a hybrid electric bus, go faster than a car, and bring down fuel and maintenance costs by 40 percent. To top it all off, the hydrofoil design that allows the ferry to glide above the water is less disruptive to the environment and wildlife both above and below the surface.


But there has to be a catch right? Seasickness. Sprinting on superfast boats first thing in the morning on a particularly windy day may sound like a surefire way to lose your breakfast to the Baltic. But Candela considered this fate in its design. The P-12 has sensors that feed into an automated control system to adjust the height, roll, and pitch up to 100 times a second to ensure a smooth ride regardless of the weather.


Despite the thoughtful design, there are still challenges Candela may face. One is speed limits on Stockholm’s inland waterways. Limits can be as low as six knows (7 mph). And when hydrofoil boats operate best at top speed this can present a problem. The reason speed limits are so low is to prevent issues caused by wake, which the P-12 doesn’t have. Thus, “The solution is working with port authorities and ferry operators to get dispensation,” Charles Haskell, decarbonization program manager at maritime consultancy Lloyd’s Register, told Wired. While in trial, Candela has a temporary exemption to Stockholm’s 12 knot speed limit.


For coastal cities like Stockholm, electric ferries would become the green public transport go-to, without the needed infrastructure of trams, trains, or subways. Charging stations will be needed, but if successful, systems like Candela’s could drastically reduce the number of cars on the road.


Other companies and cities are all aboard. Rival flying boat maker Artemis is testing its version in Belfast, while Hasselskog has held talks with authorities in Istanbul and across the Middle East. In Lyons, France, the company SeaBubbles is trialing hydrogen-powered hydrofoil water taxis. In the UK, the country’s first electric ferry recently launched at the University of Plymouth. And in Norway, electric ferries are being used to tour the country’s fjords.


Across the ocean in the States, the Biden administration announced funding to modernize ferries and connect rural communities through an electric or low-emitting pilot program earlier this year.


San Francisco was already on the electric ferry wave. According to Wired, the Water Emergency Transportation Authority (WETA), which operates ferry services in the San Francisco Bay Area, visited Stockholm to see how the Candela P-12 works.


Announced Friday, WETA was awarded $14.9 million from the California State Transportation Agency (CalSTA) to develop an electric ferry network in San Francisco. Startups have taken to the Bay as well. Sea Change, a passenger ferry built by All American Marine, prepared to launch from San Francisco bay earlier this year. Up the coast in Seattle, Washington State Ferries is also gearing up plans for their hybrid-electric ferries and electric vehicle infrastructure.


Whether its electric-powered passenger flying ferries or low-emission shipping boats, making better use of urban waterways makes sense for sustainability. “You don’t need any special infrastructure, the water is just there,” Hasselskog told Wired. “That’s probably why they were used back in the day—you just go.”



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