(Not a shipping cargo person, so take what I say with a grain of salt)
The value is cross-loading delivers greater network effects. You have many possible paths to get to your destination, and can pick the most optimal for your particular needs at each step.
Most container ships are on a sailing schedule - they visit a set number of ports, and generally stick to it (absent other issues).
So you can get out of your origin country quicker by just picking the next ship with the cheapest rates going to approximately the right location.
For the shipping lines it's more efficient to just pick up a lot of containers at once and visit multiple ports than try and get a full load to just one destination.
It also means that each port they visit they're also getting paid for new cargo for onward destinations, not running empty (or waiting for another full load) to do another trip.
The incremental cost of a pound of fuel is a rounding error in shipping. You might factor it in, but it'd be very far down the list of priorities.
Interestingly, cars have similar economics. Details vary quite a bit, but every 100lb (nearly two full tanks of gas for me) makes you 1% less efficient. It only really matters if you have driving habits that tend to burn that excess energy somewhere, like rolling in hot to a stop light and hitting your brakes rather than anticipating the light cycle and coasting in.
That’s kinda a thing for aviation: see “intermediate stop operations”.
Limiting range also lets you use smaller craft with things like smaller fuel tanks.
Iceland does quite a business on this sitting between euro and American destinations. Greenland might get into this too.
Also probably gets some crews at home each night flying the leg back instead of needing to stay on the mainland for a day/night before doing a later return leg.
I find it hard to believe the cost of docking for a few hours to refuel is > the cost of carrying and moving 2x the weight of fuel you would need otherwise. Do you have some idea of the costs?
Ships don’t use all that much fuel. A Panamax ship has a capacity of 2 million gallons of fuel and that would be ~2,600 tons. The total tonnage of a Panamax ship is ~52,000 tons.
Most cargo shipping saves fuel by just running slower.
Nope. The safety and security issues make nuclear powered merchant vessels a non starter (except for a few niche cases like icebreakers that operate in Russian territorial waters). Few nations are willing to allow an accident or terrorist attack to sink a reactor in one of their harbors. Plus you can't hire qualified nuclear engineers for low wages.
A more realistic option would be to build more large reactors on land, then use the heat and power to manufacture synthetic liquid fuel to burn in ship engines. Or to charge batteries for short range vessels.
I wonder if there is a nuclear reactor design nowadays that offsets at least some of these fears. I sometimes wonder, though admittedly as a non expert, if some of these fears that linger around nuclear power sources are behind the times.
For example, I saw a demonstration of a nuclear powered device (don’t want to say reactor per say) that was taped for a documentary I saw on PBS, it was the size of a water heater or so and had a self protection system in case of something like a rupture, that at least during the demonstration stopped it cold in its tracks preventing meltdown and made any recovered materials from tampering worthless. It was in the testing phase though, and this was at least 5 years ago. My understanding is they wanted it to power critical infrastructure onsite like hospitals but feasibly it could power a home if I recall correctly or possibly a couple homes.
Another thing I read about was using some form of partially enriched uranium as energy source for heating homes and water heating. It won’t power one but it’s not (and can’t possibly be if I recall correctly) weapons grade by any stretch of the imagination
Maybe we should as a society look a little closer at smaller reactors. Hard to say, I’m no expert
You might be thinking of radioisotope thermoelectric generators. Those can be useful for generating relatively small amounts of electric power in isolated areas. But they're very inefficient and can't scale up to the level required to propel large ships. The risk of contamination from a sinking would still remain. So not a realistic solution.
