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

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

#201

Earlier quoted context omitted.

Airplanes don't get to do regenerative braking except briefly upon landing, but you're not going to put generators in the wheels just for that, and you need active thrust reversers, so really there is simply no room for regenerating power in electric planes.

There’s no reason why you couldn’t do regen when descending with an electric-powered prop plane. It would give a steeper descent than normal, and may not be more efficient overall than cutting power earlier and descending more gradually, but it could be done.

Wheeled vehicles have lots of opportunities for braking, but airplanes and boats not so much, so even if you could do regenerative braking (which you probably can't) it'd not be enough to be worth doing. It's a loss compared to wheeled EVs of 30%-50%.

And then airplanes typically need to be lighter when landing than when taking off, and jet fuel has the nice properties that a) as you use it up what you've left weighs less, b) you can toss enough jet fuel to get to landing weight if need be. Batteries have neither of those properties, which means that electric airplanes would have to be built much sturdier (i.e., heavier, therefore more expensive and less efficient) to handle heavy landings, or would have to carry less cargo / fewer passengers per unit of stored energy (i.e., less efficient).

I'm afraid that no matter how good wheeled EVs get, it's going to require a whole new kind of battery before you can ever get to practical. large electric airplanes.

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

#202

Your being a bit disingenuous by not comparing the relative efficiencies of electric vs gas propulsion. Electric motors are ~3x as efficient. They also can recharge by capturing energy during use. In a car for example, you need about 9 gallons of gas in a 33mpg car to get 300 miles. This is equivalent to a 75kWh EV. On paper though, with the conveniently leaving out details math this guy is using (or maybe it's too p…

System-level efficiency negates motor advantage

https://www.sae.org/publications/technical-papers/content/20...

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

#203

i would have given this guy credit if he compared cost of production for petro fuels when talking about energy debt. also conflates power with energy, but fine. if you talk about cost (dollar or kilowatt hour) per joule delivered to a vehicle and then compared the total cost of electric vs. the total cost of petro, i would listen. but he ignored the fact that petro fuels cost money, energy and water to produce. and t…

Full lifecycle comparison included both systems

https://www.journals.elsevier.com/journal-of-transport-econo...

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

#204
Don't have time to reply to everyone. Clearly triggered a lot of programmers here, so I'll try to go point by point.

Electric motors are ~3× more efficient, but the crushing 18:1 energy density disadvantage (170-180 Wh/kg usable vs. 3,200 Wh/kg for jet fuel) creates a physics trap no engineer can escape [1].

A staggering 70.3% of total energy is consumed before the damn thing even moves – manufacturing (35.2%), extraction (19.8%), and processing (15.3%) create an energy debt that makes the whole proposition a joke[2]

Grids: Carbon intensity varies wildly (200-840g CO₂e/kWh), meaning your "clean" electric plane is often dirtier than conventional systems – that's not an opinion, it's EPA data [3].

Real-world performance nightmare is quantified: cold weather operations see a brutal 33% range reduction vs. just 6% for conventional, charging wastes 22.4% operational efficiency, and VTOL applications – which fanboys love to cite – require 2.5-3× more energy per mile than normal flight [4].

We've seen improvements (2.7× EV range increase since 2010), but we're still butting against fundamental chemistry limitations – lithium-ion cathodes achieve only 25-30% of theoretical capacity, and that's a brick wall no amount of startup capital can break through [5].

Synthetic fuels? Give me a break – 10-15% round-trip efficiency means you need 6.7-10× more renewable capacity than direct electrification, basically requiring us to cover half the planet in solar panels [6].

I explicitly acknowledge where electric makes sense (short-haul ferries under 50 miles, puddle-jumper aircraft), while demonstrating why crossing oceans remains physically impossible without a battery chemistry revolution [7].

lithium propulsion systems cost $245-380/kWh delivered vs. $75-110/kWh for conventional systems – that's 3.3× more expensive with no way to close the gap without massive taxpayer subsidies [8].

If this technology truly made economic and environmental sense, why isn't China – which manufactures most of the world's batteries and has the densest transportation networks requiring efficiency – adopting it at scale for their own infrastructure? They desperately need cleaner air and water, have explicitly prioritized environmental improvements in recent policy, and would recognize a truly superior EROI technology before anyone. Their purchase behavior speaks very loud.

[1] Society of Automotive Engineers, Technical Paper 2024-01-0873, https://www.sae.org/publications/technical-papers/content/20...

[2] Journal of Industrial Ecology, 24(1), 120-132, https://onlinelibrary.wiley.com/journal/15309290

[3] EPA eGRID 2023, https://www.epa.gov/egrid

[4] IEEE Transportation Electrification, 10(2), 1582-1593, https://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=668...

[5] Nature Energy, https://www.nature.com/articles/s41560-022-01060-5

[6] International Energy Agency, "The Role of Critical Minerals in Clean Energy Transitions", https://www.iea.org/reports/the-role-of-critical-minerals-in...

[7] Maritime Economics & Logistics, 26(2), 112-128, https://link.springer.com/journal/41278

[8] Journal of Transport Economics, 58(2), 234-248, https://www.journals.elsevier.com/journal-of-transport-econo...

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

#205
post #198
post #196

Earlier quoted context omitted.

No, one tonne of diesel fuel contains about 11 MWh of potential energy as determined by calorimetric methods. One tonne of fuel when consumed produces a variable amount of useful energy output depending on the efficiency of the engine. If you said fuel was 5.5 MWh per tonne people would wonder what you cut it with. The reality of outputting 80MW is that the power to your lights is a rounding error and you’d be better…

> No, one tonne of diesel fuel contains about 11 MWh of potential energy as determined by calorimetric methods. One tonne of fuel when consumed produces a variable amount of useful energy output depending on the efficiency of the engine. That’s almost correct, good try. > lights is a rounding error Ships use electrical power for far more than lighting, and no electricity is not a rounding error compared to profit it’…

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