It's not just that wind is unreliable, it's also very low energy density. You'd need a lot of sails to haul a small amount of cargo. There are applications usin

It's not just that wind is unreliable, it's also very low energy density. You'd need a lot of sails to haul a small amount of cargo. There are applications using kite sails to supplement combustion engines, but that's just an opportunistic mitigation.