The Port of San Diego unveils the nation's first all-electric tug boat | Hacker News Reader

The Port of San Diego unveils the nation's first all-electric tug boat

sandiegouniontribune.com

34 pointsCapstanlqc21 comments

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.

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

> 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

That's pretty cool, we'd often cross paths with tug boats tasked with moving container ships while sailing out on SF bay and their dual exhaust pipes are ridiculously huge relative to the size of the vessels. It's like a floating giant diesel engine with a helm+rudder attached.

I look forward to the era of day sails without the nauseating stink of diesel/bunker oil exhaust streams, probably not in this lifetime though.

> It's like a floating giant diesel engine with a helm+rudder attached

Funny. When I read the title, I immediately thought of a Naval Architecture professor who described tugs as "a floating engine with an insane amount of horsepower."

Spec sheet for the tug. https://www.crowley.com/wp-content/uploads/sites/7/2023/07/2... Edit. According to the specs, it has 2 onboard 300kw diesel generators for "long transit".

With 600kW of backup generators but 4200kW of electric motors, I think it's clear those generators aren't the main power source.

I have no idea how ports work, maybe tugs occasionally need to go between ports or something like that.

Tugboats are pretty incredible. Compared to container ships they look tiny, but they are actually pretty big. During Kings Day in Rotterdam I saw tugboats basically pirouetting in place while blasting water cannons. Way more nimble than even what I’ve seen from ski and wakeboard boats.

> the eWolf is equipped with two small generators for emergency use that allow the boat to travel longer distances at a reduced speed.

So.. not all electric. It's a hybrid diesel.

> for emergency use

This is like putting a gas generator in the bed of an all-electric truck

So the Ramcharger 1500, but in boat form.

https://www.ramtrucks.com/revolution/ram-1500-ramcharger.htm...

All ski chairlifts have a diesel backup drive motor for emergency evacuations.

Have you ever seen one run on diesel?

Would you call every chairlift in the world diesel powered?

Emergency use is a different thing

Emergency use case is not the same. The tug uses diesel for extended range tasks. The chairlift uses it during a power failure.

"Generators for long transit 2 x 300 kW"

"Fuel 9800 gal @95%"

https://www.crowley.com/wp-content/uploads/sites/7/2022/07/2...

You are misquoting. It says the generators are for emergency use, allowing it to travel longer at slower speeds.

No where does it say it uses it for extended range tasks.

The way it reads to me is "in emergencies, the speed is reduced but range is increased"

Not "we use it for everyday long range tasks"

It's not a misquote at all. It's a hybrid. If batteries are nearly flat, and there is an emergency, the tug will switch over to its diesel engine and power itself over to the emergency task.

So it's used only for emergencies?

I really don't know what we are debating at this point.

Sounds like most of the time it's going to be fully electric.

> Have you ever seen one run on diesel?

Lots of times this year alone, however I agree with your broader point.

Yes, some are hybrid:

https://en.wikipedia.org/wiki/Chairlift#Secondary_and_auxili...

Why would it need anything for emergency use? Presumably there are other tugboats around.

I don't think that's a fair assumption at all. There's a world of difference between being able to propel yoursellf versus relying on another vehicle when the emergency may occur in rough seas or busy channels.

Also the assisting tugboat would have to leave its station to assist to emergency boat.

But no, in general tugs don't always operate with a buddy.

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