@ MattB... Yes, agree Scandlines link a good one. The Flettner Rotor System becoming more widely used in marine industry/shipping. While visiting Vancouver in December 2019, I photographed the bulker AFROS which was outfitted with the Flettner Rotor System.
www.shipspotting.com/gallery/photo.php?lid=3110791

First crossing of Atlantic in 1926

https://divingalmanac.com/first-rotor-ship/#:~:text=The%20Buckau%20(later%20renamed%20Baden,engineer%20Anton%20Flettner%20in%201922.&text=On%20May%209%2C%201926%2C%20the,efficient%20than%20the%20steam%20engine.

When God wants to punish a man, he first takes his mind. The ideas of retarded ecologists can just be classified as taking one's mind. First, wind farms destroying the beauty of the landscape, oil rigs ... And now this idea. I wonder what else the madmen will give us. Time for an objection, I guess. After all, this is an open rape of beauty ...

Cheers andrecas. Good link. Was going to say it looked like a dedicated smokers chimney..

See attached link...
www.scandlines.com/about-scandlines/greenagenda/rotor-sail-mv-copenhagen

What is THAT ??