4 ms·

The recharging infrastructure for such a vessel would be an interesting challenge. Likewise if those batteries caught fire.

manquer 11mo ago
No need do charge in-situ, the ships (and ports) already transfer several times the battery volume and weight on berthing quickly . The battery systems could be designed to leverage that . Fire hazards are there for any fuel, Safety systems evolve to handle them. The environmental impact would be more localized than an oil spill.
toomuchtodo 11mo ago
Sodium batteries have substantially reduced thermal runaway risk compared to lithium. Worst case, the ship sinks during a fire and the batteries are flooded. Charging infra is likely similar to existing EV ferry charging infra. Ship pulls into the berth and starts soaking the battery storage up to 1C up until departure. Could probably use a heat exchange and raw water available for battery cooling to maximize charge current curve, actively cooling the battery storage during charging. https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2023-04/DOT-SIB-Testing-Report-Web-Version.pdf https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2023-04/... https://old.reddit.com/r/electricvehicles/comments/1m8wlou/electric_ferry_charger/ https://old.reddit.com/r/electricvehicles/comments/1m8wlou/e...
- aeonfox 11mo ago
  Na-ion cells have roughly half the volumetric and gravimetric energy density of NMC, so it's double the weight and double the space. Apart from still being at least as—if not more—expensive as LFP, they also have a sloping voltage curve, vs lithium with is relatively flat, which poses problems for voltage conversion, and these engines are going to be taking kilovolts of power. So I think those problems would need to be solved first.
  - amluto 11mo ago
    Is the sloping voltage curve that much of a problem? ISTM it might simplify cell balancing and SOC determination.
    - aeonfox 11mo ago
      I'd imagine it makes providing constant AC voltage to the engines pretty tough. It's even a problem for home energy storage because you need an inverter that can handle a very wide range of input voltages. Most inverters will cut off well before the Na-ion battery is full drained, vs a lithium which can go pretty much all the way to 0%.
      - amluto 11mo ago
        I don’t know much about the kind of giant motor that would be used in a ship, but as a general principle: the load that a motor presents to the drive electronics does not resemble your house in the slightest. To power your house (or, more generally, supply vaguely sine-wave like output at a constant voltage), you need a converter that will convert DC at the battery voltage to AC at the desired voltage. If a buck converter is used, for example, the AC voltage can only ever be lower than the battery voltage. If you use a cheap square wave inverter, it’s possible that the output and input voltages must actually be equal. A motor, though, is a highly inductive load, and large motors will and do operate from truly gnarly supply waveforms as long as the current waveform is approximately correct. Industrial VFDs (variable frequency drives) do unspeakable things involving switching a DC bus voltage across the motor via H bridges at tens of MHz, which is a horrible thing to do the the wiring between the drive and the motor if it’s not extremely short. (There are, recently, some guidelines that specific types of wire with twisted conductors, better than average insulation, and high quality shields should be used to improve tolerance of the fact that rather impressive standing waves can appear in the wiring if the wiring is a quarter wavelength or longer.). I can easily imagine designing a VFD that works just fine over a respectable range of DC input voltages by adjusting its duty cycle accordingly. One way to think of this is that a VFD looks kind of like a buck converter where the inductor is free in the sense that it’s already right there in the motor. If it’s designed right, it will handle the battery’s full voltage range, and the inductor will still be free :)
rgmerk 11mo ago
A quick googling suggests that unloading such a vessel takes at least a couple of days, more likely 3-4. Assuming two days available to charge the vessel, you'd need about 100MW continuous. Not trivial, but doable. As far as battery fires go, sure, but a) there are already a lot of electric ferries in service so designing safe maritime battery packs isn't a new challenge and b) the alternative isn't exactly risk free either; we've seen plenty of oil spills from ships.
- lostlogin 11mo ago
  The fire thing comes up with cars all the time. Petrol cars are vastly more likely to catch fire, but are a bit easier to extinguish. I can only imaging how hard it is to put out a ship fire, but is there any reason to see that the situation would be different? Bunker fuel appears to be less flammable.
  - wakawaka28 11mo ago
    >Petrol cars are vastly more likely to catch fire, but are a bit easier to extinguish. Petrol cars at most marginally more likely to catch fire, if at all. They cannot catch fire by simply being submerged in a foot of water, like an EV can. They are far easier to extinguish than EVs, which are practically unextinguishable and can reignite weeks or months later. You can use a fire extinguisher on a petrol car fire if you catch it early (they are usually electrical fires). If you catch an EV fire early, your best course of action is to run away as fast as possible. Ships are not known to be subject to fires because the types of fuel they use are not generally so volatile, and they are literally surrounded by water which can be pumped to the deck or wherever to drown any fire. Some use diesel, which is difficult to light even with a match. Others use heavy crude oil that looks like tar and would be similarly difficult to ignite accidentally. A battery fire on a ship would be a HUGE problem, as we have seen with ships carrying EVs. I think another often-overlooked risk of EVs is the arson risk. Even if batteries are less likely to catch fire (in the first few years of use, if you baby them), a bad actor can start an unextinguishable fire by shorting out or otherwise igniting a battery pack. This is easy to do and devastating.
mbirth 11mo ago
Just make the battery banks container sized and swap them out with fresh ones while doing the main cargo. Then service and charge the old ones.
- pbmonster 11mo ago
  That also means you can trivially optimize your fuel/cargo ratios. Going across the pacific? Just load 200 more battery containers. Singapore to China right after? Room for 400 FEUs more than normal.
- amluto 11mo ago
  It’s not quite “just”. A way to safely and efficiently connect and disconnect them would be needed.

manquer 11mo ago

No need do charge in-situ, the ships (and ports) already transfer several times the battery volume and weight on berthing quickly . The battery systems could be designed to leverage that . Fire hazards are there for any fuel, Safety systems evolve to handle them. The environmental impact would be more localized than an oil spill.

toomuchtodo 11mo ago

Sodium batteries have substantially reduced thermal runaway risk compared to lithium. Worst case, the ship sinks during a fire and the batteries are flooded. Charging infra is likely similar to existing EV ferry charging infra. Ship pulls into the berth and starts soaking the battery storage up to 1C up until departure. Could probably use a heat exchange and raw water available for battery cooling to maximize charge current curve, actively cooling the battery storage during charging. https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2023-04/DOT-SIB-Testing-Report-Web-Version.pdf https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2023-04/... https://old.reddit.com/r/electricvehicles/comments/1m8wlou/electric_ferry_charger/ https://old.reddit.com/r/electricvehicles/comments/1m8wlou/e...

aeonfox 11mo ago
Na-ion cells have roughly half the volumetric and gravimetric energy density of NMC, so it's double the weight and double the space. Apart from still being at least as—if not more—expensive as LFP, they also have a sloping voltage curve, vs lithium with is relatively flat, which poses problems for voltage conversion, and these engines are going to be taking kilovolts of power. So I think those problems would need to be solved first.
- amluto 11mo ago
  Is the sloping voltage curve that much of a problem? ISTM it might simplify cell balancing and SOC determination.
  - aeonfox 11mo ago
    I'd imagine it makes providing constant AC voltage to the engines pretty tough. It's even a problem for home energy storage because you need an inverter that can handle a very wide range of input voltages. Most inverters will cut off well before the Na-ion battery is full drained, vs a lithium which can go pretty much all the way to 0%.
    - amluto 11mo ago
      I don’t know much about the kind of giant motor that would be used in a ship, but as a general principle: the load that a motor presents to the drive electronics does not resemble your house in the slightest. To power your house (or, more generally, supply vaguely sine-wave like output at a constant voltage), you need a converter that will convert DC at the battery voltage to AC at the desired voltage. If a buck converter is used, for example, the AC voltage can only ever be lower than the battery voltage. If you use a cheap square wave inverter, it’s possible that the output and input voltages must actually be equal. A motor, though, is a highly inductive load, and large motors will and do operate from truly gnarly supply waveforms as long as the current waveform is approximately correct. Industrial VFDs (variable frequency drives) do unspeakable things involving switching a DC bus voltage across the motor via H bridges at tens of MHz, which is a horrible thing to do the the wiring between the drive and the motor if it’s not extremely short. (There are, recently, some guidelines that specific types of wire with twisted conductors, better than average insulation, and high quality shields should be used to improve tolerance of the fact that rather impressive standing waves can appear in the wiring if the wiring is a quarter wavelength or longer.). I can easily imagine designing a VFD that works just fine over a respectable range of DC input voltages by adjusting its duty cycle accordingly. One way to think of this is that a VFD looks kind of like a buck converter where the inductor is free in the sense that it’s already right there in the motor. If it’s designed right, it will handle the battery’s full voltage range, and the inductor will still be free :)

rgmerk 11mo ago

A quick googling suggests that unloading such a vessel takes at least a couple of days, more likely 3-4. Assuming two days available to charge the vessel, you'd need about 100MW continuous. Not trivial, but doable. As far as battery fires go, sure, but a) there are already a lot of electric ferries in service so designing safe maritime battery packs isn't a new challenge and b) the alternative isn't exactly risk free either; we've seen plenty of oil spills from ships.

lostlogin 11mo ago
The fire thing comes up with cars all the time. Petrol cars are vastly more likely to catch fire, but are a bit easier to extinguish. I can only imaging how hard it is to put out a ship fire, but is there any reason to see that the situation would be different? Bunker fuel appears to be less flammable.
- wakawaka28 11mo ago
  >Petrol cars are vastly more likely to catch fire, but are a bit easier to extinguish. Petrol cars at most marginally more likely to catch fire, if at all. They cannot catch fire by simply being submerged in a foot of water, like an EV can. They are far easier to extinguish than EVs, which are practically unextinguishable and can reignite weeks or months later. You can use a fire extinguisher on a petrol car fire if you catch it early (they are usually electrical fires). If you catch an EV fire early, your best course of action is to run away as fast as possible. Ships are not known to be subject to fires because the types of fuel they use are not generally so volatile, and they are literally surrounded by water which can be pumped to the deck or wherever to drown any fire. Some use diesel, which is difficult to light even with a match. Others use heavy crude oil that looks like tar and would be similarly difficult to ignite accidentally. A battery fire on a ship would be a HUGE problem, as we have seen with ships carrying EVs. I think another often-overlooked risk of EVs is the arson risk. Even if batteries are less likely to catch fire (in the first few years of use, if you baby them), a bad actor can start an unextinguishable fire by shorting out or otherwise igniting a battery pack. This is easy to do and devastating.

mbirth 11mo ago

Just make the battery banks container sized and swap them out with fresh ones while doing the main cargo. Then service and charge the old ones.

pbmonster 11mo ago
That also means you can trivially optimize your fuel/cargo ratios. Going across the pacific? Just load 200 more battery containers. Singapore to China right after? Room for 400 FEUs more than normal.
amluto 11mo ago
It’s not quite “just”. A way to safely and efficiently connect and disconnect them would be needed.