Thanks to IEEE Spectrum for this:
With a hundred years of history backing them, hydrofoils are known for their high speeds. Swiftness is achieved by using aircraft-like wings beneath the craft to lift the hull out of the water and “fly” above the surface to reduce drag. Their popularity peaked in the 1970s only to decline thereafter due to reasons like stability challenges, materials issues, and high production and maintenance costs.
But now, Boundary Layer Technologies (BLT), a four-year-old marine technology startup based in Alameda, Calif., aims to use the technological advances of the past 50 years to create Argo, a liquid hydrogen (LH2) hydrofoil cargo vessel, to vie with container ship and airfreight transport—the latter business alone being valued at over US $6 trillion dollars.
“Every aspect of the technology that goes into foiling ships has advanced since the ’70s,” says Ed Kearney, founder and CEO of BLT. In particular, the use of carbon-fiber composite for the wings and mast, in place of the previously used stainless steel “has solved the structural performance of the wings. They are now more slender, create less drag, and so significantly decrease fuel use.”
Traditionally, hydrofoils “have been small because of the higher energy demands of larger boats (on lift-off),” says Zhaohui Qin, who teaches computational fluid dynamics at Cedarville University, in Ohio, and who advised the college’s winning design team in the 2019 Mandles Prize for Hydrofoil Excellence. However, he agrees the reduction in weight with the development of composite materials makes larger vessels like Argo possible.
Other technology advances include computing power and computational fluid-dynamics simulation software that enables engineers to design wings using numerous iterations in fluid simulations, compared to using towing tanks, which makes Argo more economical and quicker to design.
To avoid hitting floating objects, Argo will employ X-band radar. And forward-scanning sonar will be used to detect submerged objects and mammals at ranges up to 1,500 meters, which will give pilots up to about 75 seconds to avoid submerged obstacles, says Kearney.
Argo will also have around 1.6 megawatt-hours of lithium-ion batteries on board primarily to boost the power needed to raise the hull up to 5 meters above the surface—including the payload of 200 tons, 70 percent more than a Boeing 747-400 freighter. It is designed to have a range of almost 2,800 kilometers, and a cruising speed of 40 knots—twice as fast as container ships, according to BLT.
But Stephen Turnock, professor of maritime fluid dynamics and head of the Department of Civil, Maritime and Environmental Engineering at the University of Southampton, England, queries some of BLT’s claims. “In principle, hydrofoils can go faster [than container ships] for the same installed power. But doubling the speed sounds like a marketing line. For many ship voyages, local speed limits restrict the gains that can be made during the high-speed part of the voyage.”
Qin echoes this reservation, questioning whether Argo can achieve such “speed advantages and still be economically profitable.”
Argo will carry the liquid hydrogen in 26,000-kilogram, 370-cubic-meter LH2 tanks housed in the vessel’s two hulls. A vaporizer supplies the conditioned gaseous H2 to a 10-megawatt fuel-cell stack. DC power from the stack is converted to AC and fed to motor inverters to drive the propulsion system. The propulsion system comprises four 2.5-MW motors that drive contrarotating propellers via Z-drive gearing, which enables rapid changes in thrust direction.
Kearney points out that industry has been using liquid and gaseous hydrogen for over 100 years, and consequently, safety protocols are very well understood. So he doesn’t envisage any special problems when it comes to using LH2.
Turnock agrees that hydrogen can be operated safely, which is why shipping authorities are looking into developing protocols needed to operate vessels using hydrogen and fuel cells. But he notes that the fast foiling of hydrofoils may create additional hazards, which is why they must also ensure the H2 and fuel-cell systems are sufficiently well protected in the event of a collision.
Argo is slated to launch in 2024. “We will likely have to rely on a mix of blue and green hydrogen from countries like China, Japan, and [South] Korea to service our initial intra-Asia trade routes,” says Kearney. But by early 2025, he notes Australia is due to supply Asia with 118,000 tonnes of green hydrogen annually. “And we’re already talking with producers to secure long-term supply contracts.”
Currently, the Argo team is specifying the design requirements for the major systems and modeling their performance. But Kearney says they have built, tested, and demonstrated 60 percent of the technology in prototype vessels. According to Kearney, in 2019, they completed a prototype called the P3— the first hydrofoiling container ship. It was built in 10 weeks for a cost of $150,000, as proof of concept.
The company has secured financial backing from Y Combinator, Lower Carbon Capital, and other, unnamed, backers. In addition, it has received a $180 million letter of intent from Flexport, a digital freight forwarder interested in shipping components for electronics makers in Asia, where BLT intends to begin freight services.
Meanwhile, the company plans to launch an electric hydrofoil ferry, Electra, in Q1 2024. It is designed to carry 150 passengers and cruise at 40 knots with a range of 185 km, its power coming from a 9,000 kWh lithium-ion battery system.
“Electra has more than an 80 percent technology overlap with Argo,” says Kearney. “By reducing drag by a factor of two, its power requirements are halved, which increases its speed and range.”
By launching the smaller Electra ahead of Argo, Kearney sees it bringing in early revenues, as BLT works with partners to develop its freight service.
“During the next 18 months, we will build and test full-scale Argo major subsystems,” says Kearney. Construction is targeted to begin in Q3 2023, and operations to start in Q3 2024.
The business plan calls for Argo to provide door-to-door transit times just 15 to 24 hours longer than air freight, but at 50 percent of the cost.
Given the vessel’s small size—33 meters in length—Kearney says Argo will be able to bypass congested ports and unload and reload in only 2 hours, compared to three days for larger container ships.
That’s if all goes according to plan, of course. BLT is still working to reach the functional design stage, so there is much to do and no doubt challenges to overcome before even a full-scale prototype is ready to test.
But as Turnock points out, the world is today moving both toward decarbonization and away from the luxury of flying—both of which open up a niche for new emission-free, non-aircraft-based competitors.
Qin agrees, saying Argo has the potential to compete in relatively short-distant transport markets, if its claimed efficiency and low pricing is realized.