FYI, the main innovations of these kite sails compared to traditional sailing ships are that it doesn't need masts that get in the way of cargo handling and that it requires fewer crew. In other words, it's not faster or anything; it's just cheaper.
You also need vastly less sail area and the things are more reliable because wind gets quite a bit stronger and reliable at 100-300 metres up. The system actually isn't new. AFAIU main reason for it not getting wide-spread adoption is that shipping lines, not ship owners, pay for fuel.
Modern cargo ships are so huge traditional sails wouldn't provide enough force to push them around. Neither will these kites, mind you. But, supplemental energy will still be a bonus, and a kite can reach higher and sit in faster, more stable winds.
Modern cargo ships are so huge traditional sails wouldn’t provide enough force to push them around.
Believe it or not, "proportionality" is a thing. You make the ship bigger, you make the sails bigger to match. Simple! Granted, previously, making sails bigger was limited by the weight of the things when hoisted by men operating manual winches, but now we've got motors now to solve that, and higher strength-to-weight ratio materials, too.
Point is: I maintain that, in principle, you could make a post-Panamax sailing ship -- even a traditional fully-rigged one -- if you really wanted to, and it would be capable of sailing at hull speed on wind power alone. It's just that they don't want to for reasons unrelated to technical feasibility.
Why can I only think of that journey to the center of the earth movie with the kite sail and had the one dude browsing google with the PSP. Why can I only remember two things from that movie?
“What differentiates it from other wind solutions,” says Bernatets, “is that the wing is not just pulled by the wind and countered by the ship.” Instead, it flies in figure-of-eight loops, which multiply the pulling effect of the airflow to give what he calls “crazy power.”
“Plus, we fetch the wind 300 meters above the sea surface, where it’s 50% more powerful,” adds Bernatets. The combination “explains why the power is tremendous for a system that is very compact, simple on the bow of the ship, and can be retrofitted on any ship, not just new ships,” he says.
“What differentiates it from other wind solutions,” says Bernatets, “is that the wing is not just pulled by the wind and countered by the ship.” Instead, it flies in figure-of-eight loops, which multiply the pulling effect of the airflow to give what he calls “crazy power.”
That's an innovation over square-rigged ships, sure, but not so much over fore-and-aft-rigged ones (where the sails act like aerofoils).
They're not a joke, they're a product called Seawing, made by a French company. They're being being actively tested and can be retro fitted to existing vessels rather than requiring a new design.
Correct, I think they were saying it was being reported on as if it was a joke. Not being taken seriously as a good step towards reducing carbon emissions.
Sails don't billow into the wind. They are set at an angle to it. Just enough to inflate them, creating an airfoil. The remaining wind blows across the airfoil, creating "lift" (like vertical airplane wings) that pulls the boat along more efficiently. That's why sail boats can actually go faster than the wind.
From this photo, the wind is blowing almost parallel with the sails.
The type of sail you're referring to is 'bermuda-rigged', like the smaller ones at the front of the boat in the picture. The big ones in the middle of the picture are 'square-rigged' which are really only good for sailing downwind.
The thing about those big kite sails is the wind has to be coming from pretty much astern for them to work; if the ship is sailing into even a quartering headwind they're of no use.
There's a technology...I forget what they're called, some kind of turbine, where you have a couple of tall spinning cylinders on the deck, which interact with the wind in such a way to provide thrust for the ship, this is mechanically simpler, fewer ways it can go wrong, you can just hinge them down and secure them in a storm or to pass under bridges, and they can drive the ship in quartering headwinds.
I've seen kiteboarders able to go in pretty much whatever direction they want as long as there is wind. These kites are the same thing but bigger.
That said, idk if cargo companies really want to be adding distance to the trip by tacking back and forth into the wind. My impression is that they want to get there ASAP and screw the fuel consumption.
They will slow down to conserve fuel, because when you're burning it at the quantities these ships do you're talking millions of dollars per voyage, and especially if you're going to end up waiting in line like you do at American ports...why hurry?