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?
Because faster trips means more trips per year. Even if the margins per trip is lower due to increased fuel consumption, quarterly revenue is higher. Even if significant time is waiting at port.
That said, I don’t work in the logistics industry, so I don’t have the number to say how much the difference would be.