Norsepower provides modern sails: "a spinning cylinder that uses the Magnus effect to harness wind power to propel a ship."
"When the wind conditions are favourable, Norsepower Rotor Sails allow the main engines to be throttled back, saving fuel and reducing emissions while providing the power needed to maintain speed and voyage time. Rotor sails can be used with new vessels or they can be retrofitted to existing ships."
I love that you posted an 'in the wild' solution. So many people saying this is not possible. And then someone has found a creative way to offer one alternate. Such a good example of dont listen to the nay-sayers if you want to mentally explore something. There are almost always solutions and I'm sure there are more for this one.
No one said it wasn't possible. Clearly, it's possible since ships were wind powered for millenia. The problem is that with very low fuel costs, it's not feasible because the drawbacks outweigh the benefits.
Sure sails will be used for some limited applications. But Magnus effect cylinders won't be practical for the majority of cargo ships because they consume valuable deck space and interfere with loading operations. They would only make sense if hydrocarbon fuel becomes much more expensive.
"When the wind conditions are favourable, Norsepower Rotor Sails allow the main engines to be throttled back, saving fuel and reducing emissions while providing the power needed to maintain speed and voyage time. Rotor sails can be used with new vessels or they can be retrofitted to existing ships."
http://www.norsepower.com/