This is probably a more reliable and practical solution than traditional sails.
From what I understand it's not hugely more efficient, but something like 10-20% fuel savings. Not really equivalent to traditional sails, but also much easier to retrofit and doesn't need additional crew
I think the notion was to fit masts to existing container ship and stacks, and I gsve it scant attention as my intuition (I once studied actual civil/mech engineering prior to jumping ship for applied math) suggested masts are better as integral parts of ships rather than bolt on after thoughts.
EDIT: Wingsails to reduce cargo ship fuel consumption (April 2023)
https://news.ycombinator.com/item?id=35426482
I’m Joseph, and along with Arpan and Bailey we are the founders of OutSail Shipping. We’re building a sail the size of a 747 that rolls up into a shipping container.
When deployed, it will generate thrust from the wind to reduce the fuel consumption of a cargo ship. An array of these devices will reduce fuel consumption on ships by up to 20%. These sails are easily stowed and removed to cause no interference with cargo operations.
Here’s a short video showing our prototype:
Not quite as I remembered .. kite sails, et al. are a good idea, I'm still a bit torn by the physics of a container deployed boom extension sail and the thrust transmission to the ship. Still, I haven't modeled it, so take my thoughts with a grain of salt.
EDIT2: Both links appear dead, so I guess that was a swing and a miss. Still, good to see such ideas pursued.
EDIT3: Also related
350 tons of of chocolate and wine arrive on world’s largest cargo sailboat (April 2024)
You mention container ships. I haven't seen anything explicit on these, and I think the reason is probably that they cruise much faster than bulkers and tankers, which means the potential savings from sail is smaller. I would have thought 20% optimistic even for a new-build.
My gut objection to the container approach taken above in the first link was existing container locking mechanisms for ships can struggle in severe weather to keep the boxes on the boat .. additional forces from a sail (in good weather) might well mimic the forces that break stacks in bad weather.
Your point is well taken, I might suggest that container ships could be segregated into fast and slow cargo and that might help somewhat with total fleet fuel consumption. (pure spitball notion).
It seems quite mad that we even need to debate this. Wind is free power and we have at least 2000 years of engineering to draw on how to use it.
Any propulsion unit needs to be effectively attached to a ship. Screws are attached longitudinally, low down and push. Sails are a bit more tricksy. A triangular sail mounted along the long axis will generally work best because it can handle more wind angles but a square sail mounted across the long axis will provide more power on a "reach" to a "run" (the wind is mostly from behind, so pushing).
The cutting edge of sailing ships that carried stuff are the tea clippers. Think "Cutty Sark" which is now a visitor attraction in London, Greenwich. Note the stay sails - the triangular sails at the front. Then note the three masts. Each mast has several main sails that are huge rectangles for "reaches" and additional extensions. There are even more triangular infill sails above the main sails.
It's quite hard to explain how wind and sails work but you need to understand that a sailing ship can sail "into the wind". Those triangles are better at it than those rectangles but those rectangles can get more power by being bigger. Even better, you can use the front triangular sails (stay sails) to moderate the wind to feed the other sails with less turbulent wind.
Wind is free power and it is so well understood. How on earth is this news?
> I’m Joseph, and along with Arpan and Bailey we are the founders of OutSail Shipping. We’re building a sail the size of a 747 that rolls up into a shipping container.
I suspect for any great deal of efficiency gain you’d need a similar system on cargo ships to support the forces generated.