This is in the works ... not to recharge the batteries, but literally as an assist to the existing engines: https://www.iims.org.uk/quadriga-set-become-worlds

This is in the works ... not to recharge the batteries, but literally as an assist to the existing engines: https://www.iims.org.uk/quadriga-set-become-worlds-biggest-sailing-cargo-ship/ https://www.iims.org.uk/quadriga-set-become-worlds-biggest-s... edit: I can't find it offhand, but remember also seeing a video of a startup in SF, that's experimenting with an innovative sail system for the purpose of outfitting on ferries. These sails look more like vertical wings than the usual sail (which on many points of sail is actually a vertical wing) ... and the "flight controller" would basically trim them via rotation to the ideal position when they can eke out any knots to help them preserve diesel. And if they get caught in a squall, they simple head the sails into the wind to reduce windage. So it should be a very safe system to reduce the ferry system's usage of fossil fuels. Looked like a really interesting idea.