/ 6 June 2022

How ‘flying ships’ can slash fossil fuel consumption

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Electric passenger ferries skimming above the sea surface might seem far-off but Swedish researchers believe they may soon become a reality. And, that these “flying” ships will bring major climate benefits.

A research team at the Chalmers University of Technology has created a unique method for further developing hydrofoils, which can significantly increase the range of electric vessels and slash the fuel consumption of fossil-powered ships by 80%.

Although the electrification of cars is well-advanced, passenger ferries around the world are still powered mostly by fossil fuels, according to a university statement. The limiting factor is battery capacity, which is not enough to power ships and ferries across longer distances. 

Scientists at the marine research facility, SSPA, have developed a method, tested on hydrofoil sailing boats, that can make the shipping industry significantly greener in the future, it said. “The focus is on hydrofoils that, like wings, lift the boat’s hull above the surface of the water and allow the boat to travel with considerably less water resistance.”

In recent years, this technology has revolutionised sailing. “Hydrofoils make elite sailors’ boats fly over the surface of the water at a very high speed.” 

In their study, the researchers from the university and the SSPA describe how hydrofoils are a “current hot topic” in the marine industry, both in high performance sailing and in new passenger transport systems in conjunction with electric propulsion. 

In the America’s Cup boats are sailed at more than 50 knots (more than 100 km/h) with 100% “flying” time. Hydrofoils, too, are becoming popular in the Olympics. In the 2024 Olympic games, five gold medals will be decided on foiling boats/boards. 

“The reason for the increasing popularity of hydrofoils and foiling boats is the recent advances in composite materials, especially in their strength to stiffness ratio,” said the study.

The team wants to enable the sailboats’ hydrofoil principle to be used on larger passenger ferries. “The electrification of ferries cannot be done without drastically reducing their water resistance,” said research leader Arash Eslamdoost, an associate professor in applied hydrodynamics and an author of the study.

“This method will allow the development of new foil designs that can reduce resistance by up to 80%, which in turn would significantly increase the range of a battery-powered ship. In this way, we could also use electric ferries on longer distances in the future.”

For ships that run on fossil fuels, the climate benefit could be significant, because similar hydrofoil technology could cut fuel consumption by no less than 80%. 

“At the America’s Cup in San Francisco Bay in 2013, it was the first time we saw a 72-foot [21 metre] sailing boat learning how to ‘fly’ using hydrofoils during the competition,” said Laura Marimon Giovannetti, a researcher and project manager at the SSPA and the study’s lead author. 

“And since then, we’ve seen a huge increase in sailing boats with hydrofoils. With this new method and knowledge we are able to bring together a range of different branches of engineering — naval architecture, advanced materials and aeronautics as well as renewable energy.”

Hydrofoil technology was developed in the 1960s and 1970s, when the focus was on getting boats to travel as fast as possible. Those hydrofoils were made of steel, a heavy material with higher maintenance costs. Modern hydrofoils are made of carbon fibre, a far lighter and stiffer material that can maintain its rigidity even under heavy loads — and can be tailored to the expected loads.