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I was curious and did some math based on numbers plucked from the web. A panamax cargo ship burns ~250 tons of bunker fuel a day and carries ~15k containers. C

I was curious and did some math based on numbers plucked from the web. A panamax cargo ship burns ~250 tons of bunker fuel a day and carries ~15k containers. Cruising speed is a little over 1000 km / day. The energy density of bunker fuel is approx 12500 wh / kg. Lead-acid batteries hold 50 wh / kg while high-end li-ion cells hold 500 wh / kg. By those numbers it sounds like you'd need approx 6000 tons of high-end lithium cells per day of operation - you can put 40 tons in a shipping container (much more and many ports will refuse to unload), so 150 containers of batteries per day of travel. A 5000km trip is going to use 5% of your cargo space for fuel (where previously it would be closer to 0.1%). That adds up to real money (you could have moved 750 containers at approx $5000 each, so you lost ~3.75 million, but the fuel would have only cost approx 0.3 to 1.5 million USD depending on where you fill up). For short trips (sub 1000km) I suspect they'd probably use cheaper, less-energy-dense ni-mh batteries as they are safer and cost less than half as much for a comparable charge.

tonyarkles 4y ago
I don’t have paper handy to check but in your bunker->electric conversion are you factoring in the (generally much higher) conversion loss from hydrocarbon to useful energy? Edit: looks like they’re more efficient than most ICE at around 50%. That at least cuts down the cost spread a fair bit.
ghouse 4y ago
Check the conversion of the energy content to usable energy. More of the Wh of the batteries become motive force than the Wh of the bunker fuel. Your conclusion isn't wrong; the density of the energy storage (be it bunker fuel as chemical energy storage, or batteries as chemical energy storage) matters.
morepork 4y ago
For a fair comparison, you'd have to know how big the engine and fuel tanks are in relation to the batteries and electric motors.
dymk 4y ago
That holds given today's pricing of fuel, but I expect that will change in the next couple of decades as the world decides to tax carbon emissions.
Schroedingersat 4y ago
Ni-mh batteries cost far more than LiFePO4, are not a great deal safer and last a fraction of the charge cycles. There's a reason anything bigger than a power drill switched years ago.

tonyarkles 4y ago

I don’t have paper handy to check but in your bunker->electric conversion are you factoring in the (generally much higher) conversion loss from hydrocarbon to useful energy? Edit: looks like they’re more efficient than most ICE at around 50%. That at least cuts down the cost spread a fair bit.

ghouse 4y ago

Check the conversion of the energy content to usable energy. More of the Wh of the batteries become motive force than the Wh of the bunker fuel. Your conclusion isn't wrong; the density of the energy storage (be it bunker fuel as chemical energy storage, or batteries as chemical energy storage) matters.

morepork 4y ago

For a fair comparison, you'd have to know how big the engine and fuel tanks are in relation to the batteries and electric motors.

dymk 4y ago

That holds given today's pricing of fuel, but I expect that will change in the next couple of decades as the world decides to tax carbon emissions.

Schroedingersat 4y ago

Ni-mh batteries cost far more than LiFePO4, are not a great deal safer and last a fraction of the charge cycles. There's a reason anything bigger than a power drill switched years ago.