Hydrofoil design is becoming a potential solution for passenger boats on the water faster and more efficiently, while reducing polluting emissions.
Candela’s electric hydrofoil ferry model. Image: Candela
According to Jakob Kuttenkeuler, a professor of naval architecture at Sweden’s KTH Royal Institute of Technology, hydrofoils first appeared in the late 19th century but recently, this vehicle is gaining popularity thanks to its potential to reduce emissions from small boats such as passenger ferries. Kuttenkeuler, who is known as the “godfather of hydrofoils” after many years of researching the benefits and limitations of this technology, said that the main driving force promoting vehicle use is electrification.
Early models of hydrofoils ran on fossil fuels and had heavy metal bodies. The V-shaped dual wing design helps them move faster than traditional body designs but still withstand significant drag. The resurgence of modern hydrofoils is largely due to new technological advances including smaller, more efficient batteries, ultra-light construction materials, and microcomputers that operate sensors that automatically level the hydrofoils, helping to replace the bulky V-shaped wings with elongated wings that allow the ship’s hull to be completely lifted out of the water. According to Laura Marimon Giovannetti, a researcher and project manager at Sweden’s Rise Institute, today’s hydrofoils are often made of carbon fiber combined with metals such as titanium, which do not undulate on the water surface and do not cause seasickness.
After some research, Swedish engineer Gustav Hasselskog, found that a hydrofoil design that lifts the boat’s hull out of the water could reduce energy consumption by up to 80%, turning this technology into a breakthrough for cleaner and faster public transportation. In 2014, he founded Candela and conducted the first test of an all-electric hydrofoil ferry in Stockholm last summer as part of a short-term pilot project.
Small ferries can glide above the water with the help of hydrofoils, but larger boats pose a big challenge. According to Hawsselskog, to achieve maximum speed and greatest energy efficiency, hydrofoil ships must be small in both size and weight. The vehicle also cannot travel long distances without charging and is at risk of colliding with underwater objects such as animals or logs.
Although there are still some limitations, hydrofoil vehicles are attracting a lot of attention. Hasselskog said Candela company sold 11 hydrofoil ferries to private operator JalVimana in Mumbai, India to reduce travel time on some routes. On the route from Mumbai to Navi Mumbai airport, the hydrofoil ferry is expected to reduce travel time from 1 hour 45 minutes to 30 minutes and begin operations in 2026.
In Stockholm, Hasselskog focused on a two-hour, 20km route from the western suburb of Ekerö to Stockholm city hall. The traditional ferry takes about 55 minutes to carry 250 people. Each Candela hydrofoil ferry can carry 30 people in under 30 minutes at a maximum speed of nearly 56 km/h. Hasselskog estimates that if he runs three ferries and increases the number of trips per day from nine to 23, the number of passengers that can be transported will increase by 15%. The main drawback is that the vehicle cannot travel further than 74 km and the battery pack requires an hour of charging. Candela estimates that the hydrofoil ferry will help the city of Stockholm save 40% of costs.
Kitsap, a district in the suburbs of Seattle, Washington state, USA, also recently bid to build a hydrofoil prototype that can carry 150 passengers on a round trip to the city center (about 19 km each way). Part of the design criteria was to build a model that could avoid collisions with timber floating in Puget Sound, according to John Clauson, CEO of Kitsap Transit. It is expected that the vehicle will shorten travel time to 30 minutes compared to one hour by traditional car ferry and take 20 minutes to fully charge.