Electric Ship Batteries Promise Compact, Cooler Power (spectrum.ieee.org)

35 pointsby rbanffy3 hours ago24 comments

bob1029 an hour ago

Batteries for ships seems really silly but at the same time its the perfect regime for a ridiculous quantity potentially hazardous items. Nuclear obviously works well here too. You have an unlimited amount of water with which to fight any fires or cool off equipment and you could theoretically engineer a way to dump the entire assembly into the ocean in an emergency.

Hydrodynamics are brutal, but the square-cube law works in your favor. The ocean doesn't care about what's inside your ship. Just the surface of it. The mass is mostly irrelevant. This is why cargo vessels are so large. The bigger the boat the bigger the energy density benefit.

The only real problem is the cost. To compete with a supermax you would need something like two billion dollars worth of batteries to survive a transpacific voyage.

dieselgate an hour ago

I hear you and while this is out of scope for the article a lot of sailing yachts are being converted to electric motors.

bluGill an hour ago

for sailing yachts that makes sense. They would use wind for most movement. While in harbor though they want the finer control that being under power allows - they don't need high speed/high power then though. They also don't spend a lot of time in this situation.

ZeroGravitas 44 minutes ago

Electric tugs are now a thing to do similar for big ships.

A step before that is to have shore power to run things when in port.

In general stopping pollution near populated areas and busy ports is a bigger win and so a good place to start.

lukan an hour ago

I think sailing uses mainly some other kind of energy source.

bdamm 15 minutes ago

Right. And sailing container ships seem to also be coming back into vogue.

stetrain 31 minutes ago

More modern battery chemistries are less hazardous as well. LFP for example is both cheaper and more stable, just at the cost of energy density. Which might be fine if you have a giant ship that can handle a large volume and mass of batteries to save on fuel costs.

dmtroyer 2 hours ago

I assumed they would use sea water for cooling but that doesn't seem to be the case? Maybe the battery coolant is cooled using some sort of sea water heat exchanger?

zdragnar 2 hours ago

A closed loop is probably easier to maintain compared to pumping caustic saltwater and all the things in it near batteries.

Xylakant 2 hours ago

You really don't want to cool anything with sea water directly. It's corrosive due to the salt and contains all kinds of fun things from flotsam to critters, some of which might make a home in your cooling loop. in this case, additionally, sea water is conductive and that's not acceptable in a battery.

However, feeding the coolant through some sort of heat exchange with the sea water is very likely something they do.

baud147258 an hour ago

> However, feeding the coolant through some sort of heat exchange with the sea water is very likely something they do.

Aren't ship engines usually cooled with sea water already (through a heat exchanger, not directly)? So it's not really something new

Xylakant an hour ago

Yes, that's the absolute norm (you often also want to cool the exhaust pipe itself and there you often see coolant water pumped straight into the exhaust). That's the obvious thing to do: You do have a huge reservoir of readily available coolant, tapping it is the sensible thing to do :) That's why I fully expect them to run their coolant through some heat exchange with sea water.

gpm 4 minutes ago

Fossil fuel engines are significantly less efficient than electric ones... so need a lot more cooling. I'm sure getting rid of the need for that would be a nice win that might be practical with electric engines.

msandford an hour ago

Also saltwater is conductive so if you submerged your batteries in it, you'd have an immediate short circuit. It's definitely through a heat exchanger.

pjc50 2 hours ago

The immersion fluid has to be non conductive and non corrosive. Hence the choice of oil (flammable) or weird fluorocarbons.

bluGill an hour ago

Question is can they get enough power to be useful. Marine diesel engines are very fuel efficient, fuel oil is very energy dense, and they need to run for a long time. Electric cars work in part because people expect to refuel few couple hours anyway. Enough batteries to cross the ocean is going to be vastly worse.

The only useful picture in the article is a "solar powered board", which doesn't give a good scale but appears to be barely enough solar power for the rich owner to enjoy their luxuries and will barely move all day while forced to anchor all day. I'm sure it can go really fast on battery power, but not for long. Sails would be a better primary movement source with battery for in harbor navigation or when the wind stops backup only.

Xylakant an hour ago

A lot of ships don't go across oceans and can benefit from batteries. Think ferries, feeder ships, river transport. Those all dock in relatively predictable intervals.

mmooss 42 minutes ago

As a crazy thought: On predictable routes in shallow enough water, implement an underwater power source similar in function (if not physically similar) to overhead electric bus/trolley power lines? The boats would move along their routes with a cable running down to to a connector that slides along the power source.

I'm imagining channels in a busy waterway or a regular ferry route. Of course it needs economy of scale, but at that point everyone saves on batteries, etc. Unless there are submarines, I don't know what would pass under the boat and cut the connection.

Maybe watercraft usage or routes aren't predictable enough? Maybe the sliding connector is too expensive underwater, especially in sea water.

bluGill 37 minutes ago

sea water is too corrosive and too conductive. You could make a single overhead cable and use sea water as your return work. However it wouldn't be practical since ships multiple stories tall need to pass under the wire (and draw a lot of power), while also tiny fishing boards that couldn't even get a pole that high.

jabl 12 minutes ago

The same problem with height would also be an issue for the underwater thing. Quick googling suggests a very large container ship might have a draft of 16-17m when fully loaded. Probably you want the catenary at 20m depth then. How does a small get their pantograph (or whatever you'd call it) down to that depth, and then move forwards without the pantograph sticking 20m down creating a huge amount of drag. Not to mention how do you make the connection between the pantograph and the catenary in the (conductive) sea water?

bdamm 5 minutes ago

Make the cable AC and the "pantograph" a (water tight) transformer that glides around the cable. I can't see any other way - DC is not going to work.

mathiasgredal 25 minutes ago

I had always imagined a system of autonomous submarines that function as tugboats along popular routes and then container ships would just function as barges that are hauled by these autonomous submarines. These submarines recharge their batteries automatically by docking to underwater charging stations.

bdamm 6 minutes ago

The maintenance of these power points would be astronomical, even if the basic theory could work, which I'm not 100% sure of. You'd have a single high-voltage cable, a pickup pantograph that wraps around the cable acting like a transformer that wheels along the cable, and AC current in the cable with the water itself being the ground reference. I can't imagine any other way it could work.

don_neufeld 2 minutes ago

You don’t need that - if you’re doing short routes and dock you can push enough power into batteries during docking for the next voyage.

Example:

https://global.abb/group/en/technology/did-you-know/maid-of-...