Traditional sails are very labor intensive, I doubt they will ever make economic sense again. They also take a lot of space that most ships don't have.

The two variations that might go somewhere are kites to save maybe 10% of fuel [1], or some variation of rotor sails [2] on tankers or bulk carriers that have the unobstructed deck space.

1: https://future.hamburg/index.php/en/artikel/skysails-marine-...

2: https://en.wikipedia.org/wiki/Rotor_ship

It might happen when rich countries start imposing tariffs on cargo ships using bunker fuel. Burning that stuff is utterly terrible but it's cheap so hey.

I have been seeing this prediction for a while. What makes you so confident?

I've noticed it's become an area of research again in universities. I'm sure tariffs will be put in place eventually to make shipping "greener". Harvesting wind energy seems ideal to at least reduce emissions.

I work in the shipping industry operating tugboats. I have also seen the claims that this will happen. I remain unconvinced. I haven’t seen any infrastructure changes that would indicate adoption anytime soon.

IIRC even after shipping went pretty much whole hog on fossil fuel transport there were some odd duck ships called windjammers, made with modern components like steel hulls and masts but still powered by sail. For awhile they filled a niche of transporting some types of non-time sensitive goods for a very low cost.