Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably • Hacker News Board

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#81

Post by crote » Fri, Apr 18, 2025, 10:10 PM UTC

retrocryptid wrote: post #58

PicassoCTs wrote: post #44

Earlier quoted context omitted.

Would make more sense to produce chemical from solar energy harvested on the water fuels, collect the fuel and then use this with ships

i wish there was more talk about this. it seems i heard a lot about making hydrocarbons from co2 in the air + solar or algae a couple years ago. if your hydrocarbons are made this way it seems they would be carbon neutral. i'm guessing there's more research to make it feasable since i haven't seen "carbon neutral gas alternative" at the local Chevron.

There has been quite some buzz about ammonia, as it is fairly easy to turn electricity into hydrogen, and hydrogen into ammonia. It has a reasonably high energy density, is not too nasty to handle, and already has a huge industry built around it.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#82

Post by wkat4242 » Fri, Apr 18, 2025, 10:13 PM UTC

The profitability will come when we factor in the environmental damage in the prices.

However the elephant in the room at least for aviation is that the energy per kg is about 50 higher for kerosene than for lithium batteries. A very large part of an airliner is fuel already. 50 as much? Not gonna happen. This will remain a really short range thing unless a really amazing breakthrough happens.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#83

Post by aliher1911 » Fri, Apr 18, 2025, 10:14 PM UTC

jauntywundrkind wrote: post #57

dragonwriter wrote: post #19

Earlier quoted context omitted.

Because floating solar panels add drag proportional to their area, and it takes a lot of area of panels to power a motor that is sufficient for a cargo ship even without the added drag of the panels. Also, because oceans and the things one runs into in them aren't easy on solar panels being dragged along by cargo ships.

My understanding is that drag is more about the "front-on" view of a craft than how long the craft is. Since solar panels are very thin and aimed up, it feels like they add minimal cross-sectional area to the craft. Your assertion seems trivially incorrect to me?

There's a pressure drag and skin friction drag. Friction drag is supposedly a majority component unless you sail a brick. But I don't have sources to prove that.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#84

Post by crote » Fri, Apr 18, 2025, 10:16 PM UTC

m463 wrote: post #23

The same thing could have been said years ago about solar power in california. But with PG&E's regulatory capture and people paying 50c/kwh for electricity, solar is economically practical. Even with batteries! (and wholesale electricity is still 3-4c/kwh) My point is that the math could change in a moment due to regulation and/or energy repricing. (example: disallow non-electric planes at certain airports or certain…

The math would already change quite a bit if airplanes had to play on a level playing field. For example, in the EU there are no taxes on aviation fuel. For a country like Germany that's the equivalent of a yearly 7 billion euro subsidy.

Add fuel taxes and CO2 surcharges, and same-continent rail travel suddenly becomes a lot more attractive!

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#85

Post by numpad0 » Fri, Apr 18, 2025, 10:16 PM UTC

api wrote: post #48

I remember seeing loads and loads of analyses like this back in the 2000s on a site called The Oil Drum about why electric cars would never work at scale. (Spoiler: My family has two EVs.) They always assume that the technology will never get better, that industrial economies of scale don't exist and therefore that prices don't decrease with scale, that currently developed reserves of resources like lithium equal tot…

> They always assume that the technology will never get better, that industrial economies of scale don't exist

The technology hadn't improved not much more than a quarter's worth so far in my lifetime as far as EV is concerned.

Wh/kg figures hasn't changed, even fusion seems closer than solid state batteries, mileage figures for EVs is same 4mi/kWh, battery recycling still hasn't been figured out. They can't even recover Lithium out of Lithium ion batteries. wtf.

Meanwhile, computers had gotten like, up to petaflops per nation to per building to per node. Wireless Internet went from kilobits to gigabits. Everyone wears UNIX or Linux watches.

IMO, optimistic heuristics floating around EV is too shallow. The model just doesn't have enough parameters that it's expecting growth where it should not and vice versa. It just needs way more grounding to be meaningful.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#86

Post by sightbroke » Fri, Apr 18, 2025, 10:16 PM UTC

crote wrote: post #78

sightbroke wrote: post #53

Earlier quoted context omitted.

Or Nuclear Propulsion: https://en.wikipedia.org/wiki/Nuclear_marine_propulsion#Merc... > Nuclear ships are currently the responsibility of their own countries, but none are involved in international trade. As a result of this work in 2014 two papers on commercial nuclear marine propulsion were published by Lloyd's Register and the other members of this consortium.... > This is a small fast-neutron reactor using lead–…

Nuclear ships are technically possible, but have a massive number of downsides. - The construction cost would be significantly higher than a conventional ship. - Reactors are far from trivial, so you'd double or triple the crew required. - Shipbreaking would become even more of an issue than it already is. You can't just beach a ship like this in Bangladesh and have a bunch of untrained people attack it with plasma c…

> They are an attractive option for some military ships, but I doubt anyone would be willing to risk it for regular commercial shipping.

There's been a few built over the years, mostly for research.

Russia apparently still operates one.

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

Despite hurtles you've pointed to it is still being considered:

https://www.spglobal.com/commodity-insights/en/news-research...

> This source of power confers some advantages. "You will have ships going maybe 50% faster because the fuel is essentially free once you have made the upfront capex investment," Sohmen-Pao said.

You achieve ~0 emissions AND avoid increasing transit time going with pure sailing ships.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#87

Post by ben_w » Fri, Apr 18, 2025, 10:17 PM UTC

jauntywundrkind wrote: post #57

dragonwriter wrote: post #19

Earlier quoted context omitted.

Because floating solar panels add drag proportional to their area, and it takes a lot of area of panels to power a motor that is sufficient for a cargo ship even without the added drag of the panels. Also, because oceans and the things one runs into in them aren't easy on solar panels being dragged along by cargo ships.

My understanding is that drag is more about the "front-on" view of a craft than how long the craft is. Since solar panels are very thin and aimed up, it feels like they add minimal cross-sectional area to the craft. Your assertion seems trivially incorrect to me?

Oceans can be extremely rough, but even mild waves make it inappropriate to approximate PV as thin.

The requisite area to power a ship is huge, something like 1.4km^2 (ballpark estimate for 20% cells, reasonable capacity factor guess, 60 MW consumption requirement). If a ship is about 30m wide, it's trailing about 45 km of PV. You're not even into 4 digits of cargo ships before the combined length is longer than the circumference of the planet.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#88

Post by seszett » Fri, Apr 18, 2025, 10:18 PM UTC

toast0 wrote: post #38

I suspect that there's niches where battery electric boats and maybe planes do make sense. My state's ferry system is investing in electrifying, because they project it reduce operating costs. The 'easy' part is moving towards hybrid systems that can move with diesel or battery; this is projected to save fuel even without shore charging. The hard part will be making shore charging work. Our grid is mostly hydro, so s…

We also have electric ferries here in Antwerp and Ostend. I don't think they're hybrid, although it's not clear when they get charged, I would assume during the wait times (about 15 minutes wait and 5 minutes ferrying) but I have not noticed them actually connecting anywhere, maybe I just haven't noticed though. The communication says it can sail for three hours on batteries, so they must charge during the day while operating.

And at my other place around Nantes they're building a new ferry that is supposed to be hybrid electric/hydrogen. I'm not very optimistic on hydrogen though so I don't know. The latest info say the budget has tripled and the delivery has been reported from 2026 to 2030.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#89

Post by sitharus » Fri, Apr 18, 2025, 10:25 PM UTC

toast0 wrote: post #38

I suspect that there's niches where battery electric boats and maybe planes do make sense. My state's ferry system is investing in electrifying, because they project it reduce operating costs. The 'easy' part is moving towards hybrid systems that can move with diesel or battery; this is projected to save fuel even without shore charging. The hard part will be making shore charging work. Our grid is mostly hydro, so s…

Where I live companies are moving to electric ferries because they’re cheaper to operate, require less maintenance, and are much quieter for the passengers. Plus they don’t emit any exhaust fumes while idling at the dock.

The port also has an electric tug boat, which their reports say is very handy because it changes power output much faster than diesel tugs. Charging times are not a factor according to their reports.

Our power grid is 80+% renewable though.

Of course the article ignores that it’s easier to improve the emissions of a few large powerplants than every car, ferry and scooter, and that the minerals in batteries don’t disappear after use.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#90

Post by wkat4242 » Fri, Apr 18, 2025, 10:26 PM UTC

retrocryptid wrote: post #64

baq wrote: post #36

You don’t need to rant when it’s enough to show that a few dozen airliners consume a day’s worth of a nuclear reactor power production (for some size of an airplane and a nuclear reactor; we should be accurate within an order of magnitude). Imagine every single airport needing its own huge ass power plant and you get your point across in an HN comment. Not sure what’s the point in attacking physicists, either. They s…

but the metric the OP was using was power density. nuke fuels are MUCH more energy dense than hydrocarbon fuels. but putting a reactor on each plane would probably have negative externalities. but mixing your comment with a few others, maybe a nuke plant on the ground that cracks the co2 in the atmosphere to make carbon neutral hydrocarbon fuel.

> but putting a reactor on each plane would probably have negative externalities.

Probably? It would be a disaster every time one crashes, would carry a huge proliferation and terrorism risk. Oof.

In the 50's some countries were that crazy and they even put reactors in space. Two of which crashed and one contaminated a huge area in Canada. Luckily common sense prevailed and these things don't happen anymore. Though nuclear ships still exist, there's only a few icebreakers in the civilian fleet AFAIK.