Hacker News Reader

Comment by thot_experiment | Hacker News Reader

I would LOVE a deep dive into the infrastructure necessary to charge this thing. They claim it will charge overnight, napkin math has that at roughly 3/4MW. Them's decidedly not rookie numbers. Extrapolating into the future, I imagine a busy port has some fairly reasonable number of tugboats (hard to find info on this) but for simplicity of the math let's say there are 12 and they have a 2/3 duty cycle, so we have 3MW of power being drawn constantly? I guess in the scheme of a port that might be a nothingburger but would love to know more.

View on HN

> They claim it will charge overnight, napkin math has that at roughly 3/4MW. Them's decidedly not rookie numbers.

One could argue those are rookie numbers[1]:

Bastø Electric uses batteries with a capacity of 4.3 MWh. The fast-charging system has a capacity of 9 MW, according to the shipping company.

Not sure exactly how they do it but another ferry used on-shore batteries as a buffer[2], not unlike decoupling capacitors in electronic circuits. I agree a deep dive in the charger infrastructure would be interesting.

[1]: https://www.electrive.com/2021/03/02/worlds-largest-electric...

[2]: https://en.wikipedia.org/wiki/MV_Ampere

The ferry between Helsingør in Denmark and Helsingborg in Sweden has a 10MW charger at each side, to charge for 4-9 minutes depending on the timetable. (It runs back and forth all day and all night, carrying people, cars and trucks.)

See the chapter "Robot Arm" in this video to see it coupling.

10MW is around the power for an electric freight train, so these kind of numbers aren't uncommon for a port.

https://youtu.be/rE_M1n-ClOA?t=498

https://en.wikipedia.org/wiki/MF_Tycho_Brahe

Burning 24.5 gallons of diesel makes 1 MWh of heat, so at 50% efficiency call it 50 gallons per MWh .

This makes the 6.2 MWh battery equivalent to about 300 gallons of diesel.

If you plug in this battery to charge at 1MW, it will take about 360 min to charge, so a 1 MW charging station is equivalent to a gas pump that pumps about one gallon per minute.

I do not think they are using the blue plugs shown in the picture for charging the battery. Those look like 480V 150A plugs to me, and those can only supply 0.077 MW. It is more likely those blue plugs are for "Shore Power" used while in port for stuff like like air conditioning, computers, cooking.

To charge something this big overnight you would want a more exotic type of plug, something like https://en.wikipedia.org/wiki/Megawatt_Charging_System

Reply on news.ycombinator.com