Clusters of floating wind turbines each with their own battery storage might be useful here. I imagine along strategic (ie major) shipping channels. Would it pencil out? I have no idea.

Actually thinking about it some more why not park a couple of dozen older cargo ships along major shipping route. Equip them with wind turbines and batteries in shipping containers. Now the actual cargo ships passing by can stop for a few hours, plug in and charge. Use sodium ion batteries that can support thousands of cycles. Even use regular fuel as a backup in the charging ships. You can build and maintain anywhere and then haul them to the right location.