It's possible to retrofit existing ships with some of the new approaches. Just over a decade ago the company SkySail produced a kite like system that could be

It's possible to retrofit existing ships with some of the new approaches. Just over a decade ago the company SkySail produced a kite like system that could be added to existing cargo ships to achieve multiple %age fuel savings. There's a couple of interesting quotes on the wiki page (https://en.wikipedia.org/wiki/SkySails https://en.wikipedia.org/wiki/SkySails): > There’s a structural problem slowing down the process: ship owners (who have to make the investment) often don’t pay for the fuel – that’s the charterer’s duty. The charterer on the other side doesn’t charter the ship for long enough a period to make low-carbon technologies pay back. — Henning Kuehl, head of business development at SkySails and >Fuel costs mostly get passed onto the shipper so we see little use in installing potentially expensive, untested technology to which we see no other benefit. Basically I am interested but will not be the first to try it on a large scale. — Anonymous ship owner So essentially it looks like the incentives are all in the wrong places for such technology to see rapid implementation.