Live data from Hacker News

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

kumarletter.com

121–130 of 205 posts

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

#121

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…

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.

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

#122
This post seems to either be misinterpreting facts or deliberately skewing them to argue for a specific conclusion. For example, it claims that "According to Gruber et al. (2021), a single ton of lithium extraction guzzles about 500,000 gallons of water." But the source link[1] is an abstract to a different paper titled Oil import portfolio risk and spillover volatility, which has no author named Gruber. So I have no idea if the claim is true or not. What I do know is that lithium is extracted from brine that is pumped out of the ground, then evaporated. It isn't useful for anything else, as it's far too salty for irrigation or drinking. And there are plenty of other ways to get lithium. Brines are just the most economically feasible option right now.

Another claim is, "The International Energy Agency documents that producing battery-grade lithium compounds demands 50-70 kWh of energy input per kilogram." but again, if I follow the link[2], I can't find that information anywhere. Maybe he's deriving the figure from some graph in one of the sections of the report. But assuming it's true, a typical 80kWh battery contains around 10kg of lithium, which would be 500-700kWh of electricity. If we pessimistically assume retail consumer prices, that's $50-100 worth of electricity embodied in the lithium. This is a tiny fraction of the total cost of the battery. It's 5-10 charge cycles out of the >1,000 that is expected of an EV battery.

And both of these claims neglect the fact that lithium in batteries is not destroyed over the life of the battery. It can be recycled once the battery has failed or degraded.

After that he says, "Here's the uncomfortable truth from EPA's eGRID database: the carbon intensity of our electrical grid varies by a factor of 4× depending on where you are." and links to the EPA's Emissions & Generation Resource Integrated Database.[3] Again, the link is to a general site and not the specific information he's referencing. I did find CO2 emissions per megawatt hour in the data explorer.[4] The most carbon-intense subregion I could find in the continental US was SRMW, which corresponds to most of Illinois and Missouri. Its CO2 emissions are 1,238lbs/MWh, which is 562g/kWh. Typical EV efficiency is around 250 watt-hours per mile, but let's assume 300 watt-hours per mile to account for losses in transmission, charging efficiency, etc. In that case, traveling one mile will have used electricity that emitted 168 grams of CO2. Burning a gallon of gasoline emits 8.9kg of CO2, so a gas car would need to get over 52mpg to emit less than 168 grams of CO2 per mile. Again, that's in the most coal-heavy subregion on the EPA map. I don't know where he gets the "carbon break even point" from, as it would require incredibly inefficient EVs or incredibly efficient gas cars.

There's also a claim that 70% of the energy consumption of EVs happens before they ever move. This claim is both misleading and false. To understand why it's misleading, consider a steam powered vehicle. Compared to a gas vehicle, it requires much less energy to construct than to run. But that's because steam powered vehicles are incredibly inefficient and need many times more energy to travel the same distance as a gas vehicle. EVs do require more energy to construct than gas vehicles, but they quickly make up for that by being more efficient to run. Battery production uses approximately 30-35kWh per kWh of battery capacity.[5] So an 80kWh battery will require 2,400-2,800kWh to produce. If the battery is used for 100,000 miles and then thrown away (not recycled so some of the embodied energy can be recovered), then at 300 watt-hours per mile, the battery will have stored and discharged 30,000kWh over its life. Even using these pessimistic assumptions, the battery's embodied energy is less than 10% of the energy used by the vehicle over its lifetime.

In summary, the whole post is poorly reasoned and based on information that is either misinterpreted or nonexistent. If its conclusions are correct about anything, it's by accident.

1. https://www.sciencedirect.com/science/article/abs/pii/S03014...

2. https://www.iea.org/reports/the-role-of-critical-minerals-in...

3. https://www.epa.gov/egrid

4. https://www.epa.gov/egrid/data-explorer

5. https://www.mdpi.com/2076-3298/12/1/24

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

#123

For the marine uses specifically, the use of hydrofoils promises to dramatically reduce the amount of energy needed for movement at any decent speed. Previously hydrofoils weren't used because they rely on complex feedback mechanisms to maintain ride height despite waves etc. Sure, someone could pair hydrofoils with gasoline engines, but I suspect they won't, and that means hydrofoil+electric will win out over conven…

Probably not. Hydrofoil boats work OK, but few applications need the speed. The US Navy went through a period of hydrofoil enthusiasm, and built some.[1] Boeing built a hydrofoil ferry, and some are still in service. The Navy version used 10x as much fuel per hour in hydrofoil mode, running off a gas turbine. Of course, it was going fast in that mode.

[1] https://www.youtube.com/watch?v=zQ2sSRBMPqs

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

#124

This is a really nice article, in that its long and provides a good example of knowing everything yet nothing. Setting aside individual problems with it, this is because it suffers from a broad and blindingly obvious problem: investment is occurring in this area b/c it will be absolutely politically unpalatable in 20 years to still be emitting CO2. A long analysis showing lithium is more expensive than just using gas…

Sulfur Hexafluoride and Nitrogen Trifluoride proliferate under a CO2 minimization regime. Nobody is arguing with Arrhenius proofs. Nitrogen trifluoride (NF3) is a potent greenhouse gas with a global warming potential (GWP) of 17,200 over a 100-year period, meaning it's 17,200 times more effective than carbon dioxide (CO2) in trapping heat in the atmosphere. This GWP value is used to calculate the CO2 equivalent of NF…

Who said CO2?

Who came up with the idea that someones arguing with Arrhenius proofs?

What does our proof showing the existence of other greenhouse gases help us with?

Does any of this shed any light on whether it will be politically palatable to be doing fossil fuels i 20 years?

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

#125
post #85
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 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 commonly available) while BYD is promising 1MW charging soon. A 350 fold increase with more to come.

Prices for EV batteries exceeded $1000 per kWh in 2010, down to $111 per kWh in 2025 - a 90% drop.

The technology has improved dramatically.

[1] https://www.iea.org/data-and-statistics/charts/evolution-of-...

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

#126

I recently read The Ministry for the Future by Kim Stanley Robinson, and one of the ideas in it that I thought was very good was replacing our cargo ships with wind-powered ships, basically giant sailing ships. In the book, they were incredibly slow, with shipments taking months to complete, but if supply lines were set up correctly, that wouldn't matter for a lot of cargo. Cargo ships are a massive CO2 contributor,…

Currently, ships need human sailors. They perform maintenance aboard ship as well as have legal oversight of the craft. We are not yet able to replace the crew with automation. It's difficult to find skilled crewmembers willing to sign up to extremely long rotations away from home.

But, ships need far smaller crews than they did in the past. A tall ship takes a larger crew than a steamship back in the 1980s. (I've crossed the Atlantic both ways.) Today, with automation, we have unattended engine rooms (unattended machinery spaces or UMS). You'll never totally eliminate a crew, for hte reasons you mention; but, we've reduced the size significantly.

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

#127
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…

There is a cute little two-seater electric airplane used as a trainer.[1] Gets about 50 minutes on a charge. EHang has demonstrated 48 minutes of flight with their flying car (a 16-rotor drone). Expect to see those at the 2028 Olympics, ferrying VIPs around Los Angeles. But energy density is too low for long trips.

[1] https://www.pipistrel-aircraft.com/products/velis-electro/

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

#128
post #60

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.

Also some napkin math using common examples gives a range of 0.2 - 1.2 horsepower / kg for gasonline motors, and 8 - 21 horsepower / kg for electric. So even though the batteries weigh more, the motors weigh less.

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

#129

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?

> My understanding is that drag is more about the "front-on" view of a craft than how long the craft is.

Drag (fluid mechanics generally) is... ludicrously complicated. For the typical shapes of ships, I believe you are correct that the main factor is cross sectional area perpendicular to the direction of travel, but that’s not universally true. i think that for a floating raft of panels, it would be proportional to the panel area, similar to how for winged aicraft its the wing area and not the cross section perpendicular to direction of travel.

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

#130

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…

The energy required to extract, process and manufacture lithium batteries (70% of total lifecycle energy occurs before the vehicle moves) Grid transmission losses (5-8% average, up to 15% in extreme conditions) Battery charging/discharging efficiency losses The dramatic efficiency reductions in adverse conditions (33% range loss in cold weather) For aircraft and marine applications specifically (which was my focus),…

[deleted]
Post reply on HN