Remember in the olden days when and propellers to power them across the oceans? Back then, they used massive and use that to push them through the waves, novel idea right? Well now, that on a cargo ship that’s about to sail from China to Brazil.

, the 750-foot Pyxis Ocean cargo ship has been fitted with two enormous sails developed by British engineering outfit BAR Technologies, which was spun out of Ben Ainslie’s 2017 America’s Cup team.

The sails, which each stand 123 feet tall, are built in a similar way to wind turbines in order to . They can be folded away when a ship comes into port, and when fully opened out can save one and a half tons of heavy fuel oil each day. On the Pyxis Ocean, two of these sails are being tested, which could save up to three tons of fuel every day. The BBC Reports:

The Pyxis Ocean’s maiden journey, from China to Brazil, will provide the first real-world test of the WindWings - and an opportunity to assess whether a return to the traditional way of propelling ships could be the way forward for moving cargo at sea.

Enabling a vessel to be blown along by the wind, rather than rely solely on its engine, could hopefully eventually reduce a cargo ship’s lifetime emissions by 30%.

The voyage, which is being managed by shipping firm Cargill will be the first real world , which are called Wind Wings. Along this route and future journeys, the performance of the sails will be closely monitored and BAR Technologies will use this to influence the design of future sails.

If all goes well on the test, BAR Technologies is optimistic about how the sails could shape the future of shipping. According to the company’s boss, John Cooper, half the new-build ships built could be fitted with similar sails by 2025.

With the sails installed, the Pyxis Ocean’s voyage from China to Brazil is predicted to take six weeks. On a traditional voyage powered by fuel alone, the same journey can take anywhere between 20 and 40 days to compete.