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Here's some back of the envelope math for batteries and ships:

- Weight is less of a limitation than you would think. Ship size is measured in tonnage. 40K-60K is a medium sized cargo carrying ship. So lets assume a ship like that.

- Battery weight calculations are going to be key. If you assume 170 wh/kg, 6 tonnes of battery equals about 1 mwh of battery.

- Energy usage of ships is speed dependent and it's a non linear relationship. You can save a lot of energy by going a bit slower. Going about 15 knots, a ship like this might use 15mw of power.

So the math becomes something like 6 x 15 = 90 tons of battery per hour. 5000km is about 2700 nautical miles (1 knot == 1 nautical mile/hour). So, you need about 180 hours of battery. Or about 16200 tons for a total of 15mwh x 180 = 2.7gwh of energy. That's a big battery.

The real limitation here comes from the cost of the batteries, which is dropping fast with sodium ion. The reason CATL is bringing this up is because they've been doing similar math with some informed $/kwh math. If they can get it down to around 20$/kwh, a mwh would cost 20K, and a gwh would cost 20M. So the battery would cost 54M$.

The key here is that this is still assuming 15knots. Energy usage might drop considerably if you drop it to 10 knots or even lower. You might only need 7200 tons of battery at those speeds.

The ship can handle the weight either way, though you are sacrificing useful load of course. The real constraints here are cost and speed. You pay a fat premium for a fast ship. Of course ships this size aren't cheap. A few tens of millions is normal. And they burn through many millions worth of fuel per year too. So, even though that amount of battery is expensive, the math might actually work out to these ships being cheap enough to operate that they'd earn back their battery.

You'd have to be pretty bullish about cost and performance of batteries. But CATL clearly feels that way. They have several battery chemistries at their disposal with higher densities (and cost). Over time, batteries might get cheaper and more dense. Ship designs might be optimized for batteries (e.g. structural hulls with battery). There's a lot of wiggle room here. But it's not an impossible proposition.

OK, I did some calculations based on:

* a 5,000 km electric range. * 40MW continuous power requirement for a 21.5 knot cruise speed[1] for a 14000 teu container vessel: * the size and weight capacity for the batteries being the same as the fuel capacity for a 14000 teu container vessel (taking the upper figure from [2]) * the battery pack having similar gravimetric (weight) and volumetric(size) energy density as this a modern Chinese NMC EV pack[3]

The short version is that the battery vessel would require about 25,000 tonnes of batteries for a 5,000km range under those assumptions, which compares to the current fuel capacity of approximately 13,000 tonnes. Volumetrically, it's even closer - about 17,000 cubic metres, compared to about 13,000 for the bunker fuel.

Furthermore, it's worth considering just how much cargo the ship carries. One teu corresponds to about 33 cubic metres of cargo space (not counting the space taken up by the walls of the container), so the ship can carry about 462,000 cubic metres of cargo. So the additional space required to carry an additional 3,500-odd cubic metres of batteries corresponds to only about 0.8% of the ship's total cargo-carrying capacity.

I was surprised at just how doable this is, to be honest. What threw me is just how much bunker fuel ships can carry; if I'm doing the sums right, a ship like this can carry enough fuel to circumnavigate the globe a couple of times over. It may well make economic sense but it's not really necessary to have that kind of range to operate the ship safely.

[1]https://www.man-es.com/docs/default-source/marine/tools/prop... [2]https://www.freightwaves.com/news/how-many-gallons-of-fuel-d... [3]https://www.batterydesign.net/zeekr-140kwh-catl-qilin/

Hybrid propulsion is already a thing in the marine world (often in navy/military designs):

* https://en.wikipedia.org/wiki/Combined_diesel–electric_and_g...

* https://en.wikipedia.org/wiki/Combined_diesel–electric_and_d...

* https://en.wikipedia.org/wiki/Integrated_electric_propulsion

Ships sail at the cost of static resistance in water. Larger ships are more efficient, once buoyant. There is a New Scientist story about a guy on guard duty moving a moored navy boat by leaning on it, for a long period of time.

TL;DR marine is the one niche where "we had to make it a lot bigger to hold the batteries" isn't actually a big deal. If you do this the right way, you still have heaps of volume for cargo, and solar cells on the hold covers.

Since there is a lot of space out there in the ocean I wonder if some kind of big floating energy station could be a thing, using middle of the ocean wind, tidal or solar. I guess you don't have to pay anyone for the space or worry about too many regulations etc.

I did some fast back of the napkin math on the idea of sahara solar + electrified shipping + sodium ion batteries. A lot depends on the, as yet, fully disclosed pricing of sodium ion batteries but the trend in pricing, and capacity, is clear and the price point may have already happened to make this viable. One thing is clear though, even if my napkin math was massively optimistic and it isn't economically feasible now it will be shortly and at that point energy production around the world is potentially disrupted. Ships can pull in and feed the grid directly or offload containers and onload empty ones to make the trip back for cheap, clean, renewable power. It is looking more and more viable to ship electrons like we do for oil and that is a major game-changer.

This is overly optimistic.

If you expect _oceanic_ ships in 3 year, you need to start building infrastructure today, in multiple ports.

If you need to build those infrastructure today, you need to have something standardize.

otoh, if all you want are just some prototypes, we have them today already..

I guess I want to know "oceanic" means in this instance. Is that just going out into the ocean a short distance? They mention the "Yangtze River Three Gorges 1" river cruise ship as an example. This thing has a range of like 100km. It seems we are far away from making true oceanic crossings of any long distance and I doubt that is coming by 2028.

We already have electric oceanic ships. They’re called nuclear submarines.

Allseas is putting the reactors on their vessels as well iirc.

It would be amazing if they could leverage the container system, but instead of goods, there'd be battery containers they could just plug in to the ship. You could even charge a battery container somewhere and bring it in by (electrified) rail.

I am very skeptical. Battery tech is still far away from the energy density of diesel fuel. How far could an electric ship go and what could it carry?

The US with its sunk cost and political power base in fossil fuels is losing the innovators dilemma at a large scale here.

I wonder if nuclear containerships can be developed and have enough power to pull a train of containerships.

I guess if it works for cars then boats should too

Cars have regenerative breaking which is a help in urban areas.

Ships tend to go not change course nearly as much on a several day journey. I guess a propellor could run in reverse for regenerative breaking, but it wouldn’t help much.

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.

Sails [0] [1] [2] are obviously more sustainable than the gigantic industry needed around batteries this size. That'd of course massively increase the cost of shipping and suddenly producing most things locally would make more economical sense. Bye bye £2 jeans from Shein.

[0] https://www.towt.eu/en/home/

[1] https://www.neoline.eu/

[2] https://graindesail.com/fr/voilier-cargo-grain-de-sail-3/

Is it possible for ocean vessel to generate from sun panels as much as needed for moving? I would suggest vessels does not need scarce Lithium, it is too needed for some other uses.

For a vessel the size of a container ship, mounting an SMR (Small Modular Reactor) directly to power it would likely result in less energy loss.