[elihu]

I wonder if electric ships could be a reasonable option? I don't have enough of the relevant numbers to do the math on whether a modern cargo container ship with some fraction of its mass dedicated to (perhaps) lithium iron phosphate batteries at about 150 watt hours per kilogram would be able to go any reasonable distance.

If we assume for the sake of argument that it's not enough for most reasonable-length routes, maybe if there was charging infrastructure at regular intervals that would help? I'm imagining for example a ship crossing the Pacific from the U.S. to China, but stopping in at Hawaii, the Marshall islands, and the Phillipines to charge. Maybe not even in a port; maybe there'd be power lines that run out to buoys that have the maritime equivalent of a DC fast-charger.

Also, one could imagine overhead lines being installed over the Panama and Suez canals. Ships could reach up with pantographs and charge their batteries as the traverse the canal.

The extreme case would be to have power lines that stretch from one continent to another, and ships cross whole oceans without ever unplugging. I'm not sure how that would work, exactly: floating cables? Cables that run along the sea floor, but the ships run an extension cord that drapes down to meet it? Lots of mechanical problems that would have to be solved.

Even with charging infrastructure only available in some places, if ships were configured with diesel engines that can take over when the batteries are dead, running off of batteries at least part of the time could reduce the fuel consumption by quite a lot.