...AND CHEAPER...:

The Oceanbird Wing 560 isn't a wing, but it isn't a sail either. When it's first assembled a few months from now in a shipyard just north of Malmö, Sweden, it'll be 40 meters high with a 560-square-meter surface and will weigh around 200 metric tons. Its creators call it a wingsail, and they think it's the future of sea travel.

"It's more like an airplane wing that you put on top of a ship rather than a normal sail, that's why we call it a wingsail," says Niclas Dhal, managing director of Oceanbird.

The wingsail consists of two parts: a rigid main core and a flap that draws air onto the core in a system inspired by high-performance racing yachts, which can travel faster than the speed of the wind. The core is made of steel, surrounded by glass fiber and recycled PET, and the whole thing can contract to less than half of its total length and tilt down to lie flat over the deck. This summer, its prototype will be tested on land, and next year it will be fitted to a 14-year-old cargo ship, the car carrier Wallenius Tirranna.

Making the sail work on a vessel that's already in service is critical for a company that wants to help decarbonize the shipping industry, which is responsible for just under 3 percent of global greenhouse gas emissions. Building more fuel-efficient ships is the long-term mission, Dhal says, "but if you really want to change the world, you need to address all the existing vessels."

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