The Guardian article glosses over a few things that are actually interesting about this ship:
- It's made out of aluminum instead of steel. The resulting weight savings make it a bit more efficient. That's something this shipping yard specializes in.
- Because it is going to run in shallow water on the river Plate, it doesn't actually have propellers but a water jet propulsion system.
The project of getting this ship from Tasmania to South America is also going to be interesting as well. It can't do it under its own power; it's designed for a ~50km crossing, not a trans Pacific/Atlantic journey. At the time, they were thinking tug boats.
I'd wager they will use what is known as a 'Float-on/float-off' ship for transport... it's rather common actually-
It's a ship with a very low deck line that partially submerges itself, with the center of the deck underwater deep enough so the other vessel can 'float on' over the deck. They they pump the water back out, raising the deck above water and the boat on top it just rests flat.
> The project of getting this ship from Tasmania to South America is also going to be interesting as well.
Indeed. As I remarked last time (1) "it's long distance and can be rough seas" They get to pick a good time of year, but either route goes past places known for storms and shipwrecks in the winter (June to September). Would you choose to go via Cape Agulhas or around Cape Horn?
It would be annoying to be ready to deliver the ship, but due to schedule over-runs, to have to wait 4 months for the weather to improve.
If it’s anything like the electric ferries that cross the Öresund beween Helsingborg and Helsingør, they grab charge while they’re unloading and loading at each terminal:
Each trip consumes approximately 1,175 kWh, which is nearly the same amount a residential home consumes in a month. In each port is a tower with a robot arm that connects the charging cable automatically every time the ship comes to the dock. The system charges 10.5 kV, 600Amp and 10.5MW. The batteries have a total capacity of 4,160 kWh, which means that we always have a surplus of electricity if for some reason we cannot load during a stop or if the transit takes more time than usual.
In Helsingör the ferries charge for approx. 6 minutes and in Helsingborg the ferries charge for approx. 9 minutes. This is enough to suffice for the journey across the strait.[1]
Side note: you can also charge your car on board from the boat’s batteries.
The Cruise Ship Terminal in San Francisco has 12 mW. Apparently it's uncommon in that it's wired with enough power available so the cruise ships don't have to run their on board generators while docked in port here. It's a major pollution thing.
> The ship... will travel between the ports of Buenos Aires, Argentina, and Colonia del Sacramento, Uruguay. The two cities are 60 kilometers apart, a distance it is expected to travel in 90 minutes.
> Direct-current charging stations will be installed at each port... A full charge is expected to take just 40 minutes.
Something people overlook with these things is that you don't actually need to fully charge batteries because they won't be completely empty and probably a 70-80% charge is more than enough for a single crossing with a healthy safety margin. Also charging speeds are non linear. Charging speeds typically drop when the battery gets closer being full. Charging from 80% to 100% is a lot slower than charging from 20% to 80%. And depending on the battery chemistry, completely discharging or charging them to the max isn't necessarily great for battery longevity.
Another point with battery powered ships is that the rate at which they discharge is speed dependent and that's a non linear relationship because the drag increases quadratic with speed. So, if you are at 30%, you can still make it across. Just not at the full speed. This is less about range anxiety than it is about just being able to stick to schedules. If the ship did not charge enough it would have to go slower. But it would still get there. This ship is designed to go quite fast which means it would have a lot of wiggle room. So they might make it across at full speed even at maybe a 60% charge. The risk is that they'd run low and might have to slow down a bit. It would get there but with a delay if that happens. And then it would have to sit there a bit longer recharging leading to more delays.
The trick is optimizing the amount of batteries to minimize turnover and delays; not around being able to charge them from 0 to 100%. The sweet spot is probably around the 20-80% mark, meaning you'd want to be able do a crossing at full speed using about 50-60% of the battery capacity. The rest is just there as safety margin to avoid delays. If you burn into that, you need to charge a bit more. With 40-50 minutes turnover, there's plenty of time to do that typically.
Indeed, that's why I say "keep charge", i.e. be in a steady state such as always leaving at 80% charge. Not charging from zero, and not necessarily charging to 100%.
People who charge electric vehicles at home emphasise that you plug it in as a matter of routine every night (ABC: Always Be Charging) and since it's software-controlled, you can e.g. tell it to charge up to 80%, and figure out the most cost-effective way to do that by 8am.
The ABC of such a ship, is that it would be plugged whenever it is docked, during the turnarounds. And there is enough time in that turnaround to keep charge. It likely also has some downtime at night as well, but that matters less in this case.
I think that makes a ton of sense, esp since you can retrofit diesel-electric ferries.
Skips expensive DC charging infrastructure, but does require to buy two batteries which can get expensive. Over time vpp / market arbitrage can pay for battery itself tho.
Also sacrifices some of the cargo capacity. I.e. for wellington - picton that’s about 4 rail cars or 6 semi trailers.
apparently, 40MWh of capacity is enough to travel 40 nautical miles. The distance between Tasmania and South America is around 6,500–7,500 nautical miles.
It also needs to beat up that air enough to make the resultant forces overcome gravity acting on the airliner whereas the ship just gets to float there.
- It's made out of aluminum instead of steel. The resulting weight savings make it a bit more efficient. That's something this shipping yard specializes in.
- Because it is going to run in shallow water on the river Plate, it doesn't actually have propellers but a water jet propulsion system.
Fully charged did a video on the construction of this ship early last year: https://fullycharged.show/episodes/electric-ferry-the-larges...
The project of getting this ship from Tasmania to South America is also going to be interesting as well. It can't do it under its own power; it's designed for a ~50km crossing, not a trans Pacific/Atlantic journey. At the time, they were thinking tug boats.