Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

kumarletter.com

Post reply on HN
Print view View original

141–150 of 205 posts

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

#141

Post by numpad0 »

derriz wrote: post #125
numpad0 wrote: post #85

Earlier quoted context omitted.

> 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 rec…

> The technology hadn't improved not much more than a quarter's worth so far in my lifetime as far as EV is concerned. Average EV range has increased 2.7 fold in the years 2010 to 2021[1] and has continued to increase - by 40% since then. Neary a 4-fold improvement in 15 years. Charging tech has improved from the initial Level 1 (1kW) and Level 2 (13kW) technology to fast charging (150kW) or 350kW (current fastest co…

> Average EV range has increased 2.7 fold

Don't dodge the question like that. I said efficiency hasn't improved. You basically said, the car got 2.7 fold bigger.

Consider that Gen1 Nissan Leaf already had 24kWh battery and 200km(125mi) rated range. Today's EV with 100kWh battery packs has at most 500mi - literally zero improvement.

CHAdeMO supported up to 62.5kW since 2009 or so. It can do 400kW now, that's still not even 10x improvement.

Battery cost did marginally decrease. Currency inflated a bit over time. Battery capacity increased accordingly from those. And you spun that into a "350 fold increase".

Shame on you.

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

#142

Post by numpad0 »

GaggiX wrote: post #60
MegaButts wrote: post #50

Earlier quoted context omitted.

> reduced weight in other parts of an aircraft The bigger problem is that the overall weight increases. Rearranging the COG doesn't really matter when most of your energy is spent literally fighting gravity. This is the first thing that popped up in google when I wanted to compare gravimetric density between gasoline and lithium ion batteries. Gasoline is still approximately 30x denser. That is at least one revolutio…

Considering the thermal efficiency of a modern jet engine, the usable energy compared to a lithium battery will be ~15 higher per kg, still bad, but not as bad.

Doesn't it compound since it costs fuel to carry fuel in a flying machine?

I'm not sure about math but isn't it like 1/15th Isp, even with that maximally optimistic value?

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

#143

Post by cagenut »

generalizations wrote: post #77
lukev wrote: post #65

Earlier quoted context omitted.

I chose those examples specifically because they were completely successful.

Those were; many were not. Someone who takes issue with the middle class of the USA might not be.

you're committed to the username bit

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

#144

Post by xbmcuser »

fragmede wrote: post #121
ChuckMcM wrote: post #63

Earlier quoted context omitted.

Was going to post something similar. I love me a screed where the author rails against some group saying they don't know what they are talking about, and then goes on to demonstrate that they don't know what they are talking about. :-) For a long time I didn't understand what 'talking past each other' meant but this article is a good example of that. Mostly it's bad form to make sweeping generalizations. But let's be…

In the larger discuss is of course, solar panels, and how they can be installed cheaply enough and with enough storage to make it feasible. Vertical integration is the key here and yes it's additional initial capital outlay, but if someone wants to run the numbers, I bet there's somewhere where it makes sense.

He is wrong on the price of electricity by a factor of 100. The LCOE of solar and Bess is below cost of coal in China already ie around $0.04-0.05/kwh. Recently UAE signed a contract for 1 Gwh 24 hour solar and BESS supply for 10 years at around $6 billion which is approximately $0.07/kwh but after 10 years the solar and batteries will still be working at 85-90% capacity cost 0.

I cant say about planes but as far as ocean freight shipping goes we are very close to the tipping point. Battery prices have already reached a point where it is cheaper to go battery electric for small voyages.

https://www.nature.com/articles/s41560-022-01065-y

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

#145

Post by Panzer04 »

0xbadcafebee wrote: post #100

I came to the comments hoping for lots of electric apologists not reading the article and I was not disappointed As a recap (for those who don't like to read) - 70% of EV cost comes before the vehicle ever moves and must be recouped over the life of the vehicle (and takes much longer than traditional fuels) - the energy density & cost of certain fuels is the only reason certain vehicles are able to be profitably oper…

What do you mean? Virtually no one is arguing that marine or air is viable given current tech.

The article author though demonstrates some clear lack of understanding about more viable tech though, given his absurd assertion about the profitability of EV scooter companies. Ground-based EVs like cars and ebikes are clearly here to stay and are going to replace almost all fossil-fueld based equivalents.

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

#146

Post by pfdietz »

lawrenceduk wrote: post #139
pfdietz wrote: post #118

Earlier quoted context omitted.

One possible path is the hybrid aircraft, where combustion turbines or fuel cells produce electric power that drives small ducted fans via electric motors. The enabling technology here is superconductors. Airbus is working on superconducting motors and generators for such hydrogen-powered aircraft. One can imagine regenerative braking in the fans, for example to recover energy as aircraft descend, and also with batte…

Pilot here, I don’t think this is right. Aircraft typically operate at 80-100% power output. It’s not the average 20% power output of your car. Weight is pretty much everything, the savings from regenerative braking in an aircraft are almost 0% but the cost of enabling it is some tons. This tech makes loads of sense in a car but I’ve never flown an aeroplane in stop-start traffic because that’s not how the sky works.

I don't see how that can possibly be correct, at least for commercial airliners.

An airliner will use maximum power at takeoff, somewhat less for climbing, and much less during cruise. The figure I see is takeoff fuel consumption/hour is like 3x cruise fuel consumption/hour. Power needed will also decline as fuel is burned off, since the required lift goes down.

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

#147

Post by Panzer04 »

kumarski wrote: post #110
philipkglass wrote: post #33

Earlier quoted context omitted.

I believe that by 2050 synthetic hydrocarbons made from carbon dioxide and clean electricity will be deliverable at a real (inflation adjusted) cost less than than 3x current oil prices, on an equivalent-energy-content basis. That could more than double the costs of a transatlantic flight, but still wouldn't price it out of reach of the upper middle class. Synthetic methanol made with renewable energy has already bee…

At 10-15% conversion efficiency, you're burning 85-90% of your energy just making the damn fuel, requiring 6-7× more renewable infrastructure than direct electrification. Current production costs are $15-25/gallon (not the fairy tale $2-3/gallon of jet fuel), and the physics won't magically improve to hit their "3× oil prices by 2050" fantasy. To replace global aviation fuel would demand a staggering 32,000 TWh of ne…

You've not actually addressed the cost points he makes. You seem to bediscounting the sheer cost effectiveness of renewable power because if an ideological opposition to it.

The wonderful thing about looking at how much something actually costs is you don't need to do all the work yourself - just look at the expense of the inputs and calculate your output. Solar panel electricity is absurdly cheap.

In any case it's obvious that current direct electrification is not feasible using current battery tech, so alternatives need to be explored. Unless we find a battery tech with 10x energy density batteries aren't likely to be viable in the air.

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

#148

Post by Panzer04 »

kumarski wrote: post #114
trhway wrote: post #43

Current lithium batteries Tesla - 270+Wh/kg, cheap AliBaba - 250+Wh/kg. Gasoline/jet fuel - 12KWh/kg, with 30% thermodynamic efficiency - 3.6KWh/kg. If one takes into account piston engines weight and their expensive maintenance or how expensive jet engines overall, the electric seems to have a very good niche of short range planes, and for multi-rotor VTOL it is unbeatable.

Factor in complete system requirements—cooling, casings, and safety systems—that 270 Wh/kg battery delivers only 170-180 Wh/kg of usable energy. Jet fuel still maintains an 18-19× energy density advantage (3.2 kWh/kg vs. 0.17 kWh/kg) at the system level, which explains the fundamental range limitations we're seeing in electric aircraft development. For VTOL applications specifically, it demands 2.5-3× more energy per…

I'm sorry, what? That is an absurd assertion. Batteries are incredibly efficient, like 95-99% discharge efficiency for capacity. They're already bad for this use case, exaggerating it just makes you look bad.

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

#149

Post by XorNot »

svnt wrote: post #106
MostlyStable wrote: post #25

Just going off the tweet about electric scooters being a scam: Nothing in that tweet is convincing. Let's just take at face value the assertion that a KWh of energy in an electric scooter costs $5 (as an EV owner: I'm skeptical). I'm going to use Lime (an SF based scooter rental company, chosen at random) as an example. I tried finding exact battery specs, and couldn't, but based on the range and some general scooter…

He is for some reason comparing the levelized cost of energy. This is a metric used to analyze energy generating devices, not energy consuming devices. His tweet says that if you wanted to buy electricity from an electric scooter and use it to run your house, it would cost the utility providing it $2 to $5/kWh, assuming that the sole function of the scooter is to provide its electricity to consumers directly. LCOE go…

Electric marine operations seems like it makes more sense if you plan to do something clever with solar panels to generate electricity as you go, rather then try to store it all up front (I don't know what, flexible solar panels on a big parasail maybe?)

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

#150

Post by XorNot »

staplung wrote: post #96
jmward01 wrote: post #9

This appears to ignore the new technology that electric brings in: Reduced maintenance, (for aircraft) reduced weight in other parts of an aircraft, new propulsion capabilities that increase efficiency of the energy used, new performance envelopes (like flying much higher because the physics are totally different), etc etc. Sure. Take an existing vehicle optimized for burning things and just swap that small part and…

Other than potentially reducing maintenance costs, I'm not sure any other part of this stacks up. I don't see how electrification would allow you to save weight in other parts of the aircraft. I don't think electrification adds any new propulsion capabilities that are more energy efficient, not for airplanes or boats anyway. For boats, the electricity would still be turning a screw and for airplanes the only method o…

Storing and producing aviation grade fuel is a considerable expense and logistics chain (unleaded AVgas replacements are still not generally approved - if you live near a small airport you've been getting dusted with lead fumes for decades).

An electric plane dispenses with that: it can functionally be charged up anywhere there's any sort of electric service.

Post reply on HN