The power required would be the same as that provided by the bunker fuel engines in common use. Modern, computer controlled sails are efficient and very powerful. It’s obviously working for this ship, which is a conservative build.
> The power required would be the same as that provided by the bunker fuel engines in common use
And that is a lot of power! Emma Mærsk has an engine output around 80-90MW.
The largest off shore wind turbine today is 26MW with a rotor diameter north of 300m/1000ft(!!). Common (modern) offshore wind turbines today are about 10-15MW with rotor diameters of ~220m/720ft.
I will not conclude it is impossible at this end of the scale, but you need a huge foil area to match such engine output.
