The problem with running any kind of transportation with electricity is that it requires heavy batteries. This is a particular problem for the boats as they suffer from drafts in the water. To solve this, Candela uses hydrofoils, legs that extend into the water and act as wings that propel the boat up into the air while it takes off like an airplane during takeoff. “In the harbor, the foils are completely retracted, so they are protected,” says Hasselskog. “But then you lower the foils and hit the throttle and it starts. The control system takes care of the entire take-off sequence, it’s like an airplane. ”
Hydrofoil boats are not new, but electric power and automated control are. The Candela P-12 carbon fiber will have dual propulsion systems powered by 180 kWh batteries that let it run for three hours before being charged. With a length of 12 meters and 4.5 meters across, the 8.5 ton boat will carry 30 seated passengers.
A super-fast flying boat sounds like a safe way to lose your breakfast in the morning, but Candela has sensors that are fed into an automated control system to adjust the height and roll and pour up to 100 times per second to ensure a smooth ride regardless of the weather. “Through the control system, we can rule out any vertical movement of the boat,” says Hasselskog, which is what tends to cause seasickness. “No one has been seasick on our boats so far.”
All this means that the Candela P-12, when built, will need less energy per second. passengers than a hybrid electric bus, drive faster than a car and reduce fuel and maintenance costs by 40 percent. And as it glides over the water, it is less disturbing to the local environment both above and below the water.
Candela could not just increase the size of its existing boat to build the P-12 – the rules require a thicker hull, fire safety systems for the batteries and, confusingly, separate toilets for passengers and the lone crew member who must drive at all times.
Apart from toilets, there is another regulatory challenge: Inland waterway speed limits tend to be as low as six knots (7 mph), but hydrofoil boats are most effective at top speeds. Such speed limits are for safety reasons and to reduce alertness, which both as P-12 does not cause. “The solution is to work with port authorities and ferry operators to get dispensation,” says Charles Haskell, program manager for decarbonization at the maritime consulting firm Lloyd’s Register. Around Stockholm, the border is 12 knots, although Candela has one temporary dispensation during the trial.
Not all cities can use waterways like highways like this, but it could be an appealing idea for coastal urban areas. Rival aircraft carrier Artemis is testing its version in Belfast, while Hasselskog has held talks with authorities in Istanbul and throughout the Middle East. Representatives from the Water Emergency Transportation Authority (WETA), which operates ferry routes in the San Francisco Bay Area, have visited Stockholm to see how the Candela P-12 works.
For coastal cities like Stockholm, ferries could become the water equivalent of trams without having to lay infrastructure such as railways, although charging systems will be needed. “If it works as an offshore light rail that facilitates hundreds of people who would have been driven by car, then that’s what we need more of,” said Paul Chatterton, professor of urban futures at the University of Leeds. “Speed is a red herring … in a metropolitan environment you need big big crafts that can take many people short distances.”
Hasselskog claims that a large fleet of smaller boats offers more flexibility than larger ferries and can mean that they are used as needed, eliminating the need for sailing schedules or fixed stops. The idea is also being touted by hydrogen-powered hydrofoil water taxis made by Sea bubbles, who has been prosecuted in Lyon, France. Smaller boats have another use: to ferry maintenance personnel and supplies out to offshore wind farms, says Haskell, who solves a problem by getting staff to places many miles offshore without arriving seasick.
Even without top speeds, water taxis and boat buses promise cities with waterways, Chatteron says, pointing to the popularity of Venice vaporettes. And in addition to passenger transport, slow, electric canal barges could remove goods from the roads. “You can move a lot of things with little or no energy,” says Chatterton, “and many European cities have channels.” Whether it is electrically powered flying ferries or low-energy barges, better utilization of urban waterways makes sense for sustainability, says Hasselskog. “You don’t need any special infrastructure, the water is just there,” he says. “That’s probably why they were used back then – you just have to go.”