In terms of cleaning up and decarbonizing shipping, nuclear power is a more natural fit in my opinion. Very high power density for long periods of time. Proven practicality and appropriate safety for decades by the Navy.
To deal with ports not wanting them to come in, you can use ocean-faring nuclear powered tugs that hand-off long-haul cargo barges to electric or fossil tugs for the final 10 km.
This was tried in the 1960s (see N.S. Savannah [1], Otto Hahn, etc.). Russia actually operates a nuclear powered cargo ship today (Sevmorput), though it does cause problems e.g. when the propeller breaks on the way to Antarctica and no shipyard will let you in [2].
The key is to mass produce them in such a way that economies of mass production can be used to alleviate the challenges of nuclear costs. Interestingly, this also parallels with options to help decarbonize the world with shipyard-constructed offshore nuclear power stations [3].
Security and piracy would be a new challenge, but I still think it's worth it to avoid all the current killer air pollution and CO₂ emission. You could make the core basically inaccessible except when in an outfitted maintenance shipyard and have a priority mobile security force to respond to such incidents. The ships should be designed to have a fail-safe sink function where it sinks and maintains the core integrity using seawater convection until a designed salvage operation can occur.
I, for one, cannot wait until Somalian pirates become nuclear-armed crime syndicates. I've always wanted to live in the worst bits of cyberpunk dystopias.
To deal with ports not wanting them to come in, you can use ocean-faring nuclear powered tugs that hand-off long-haul cargo barges to electric or fossil tugs for the final 10 km.
This was tried in the 1960s (see N.S. Savannah [1], Otto Hahn, etc.). Russia actually operates a nuclear powered cargo ship today (Sevmorput), though it does cause problems e.g. when the propeller breaks on the way to Antarctica and no shipyard will let you in [2].
The key is to mass produce them in such a way that economies of mass production can be used to alleviate the challenges of nuclear costs. Interestingly, this also parallels with options to help decarbonize the world with shipyard-constructed offshore nuclear power stations [3].
[1] https://en.wikipedia.org/wiki/NS_Savannah
[2] https://thebarentsobserver.com/en/nuclear-safety/2020/11/mec...
[3] https://whatisnuclear.com/blog/2020-01-26-offshore-power-sys... (disclaimer: my site)