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webfarmer has a post about wind-powered boats , so I got to thinking about bigger things.

Preliminary findings:

There is Flettner's rotor ship, which webfarmer mentions. It appears on the cover of Popular Mechanics in 1925

These days, there's obviously a bit of thought (and money) being put into wind-assisted ships, where a large kite provides part of the power alongside the traditional fuel motor. These are very big boats.

For a cargo ship driven totally by renewable energy, there's the futuristic Orcelle. There's a lot a talk about this one, type 'Orcelle' into Google

Another renewable energy alternative are solar ferries.

Going back a century or more though, could ships powered by wind turbines/rotors be an alternative to traditional sails? If they were faster, able to sail into the wind, used less crew and maybe less reliant on the fickleness of wind. Would they be practical though? Reliable? Affordable? Doable?

Or what about wave-power as a supplement to sails?