4 ms·

Completely agree. I had a thermodynamics teacher in college say “in the history of transportation we’ve never switched to something powered by lower energy dens

Completely agree. I had a thermodynamics teacher in college say “in the history of transportation we’ve never switched to something powered by lower energy density [than the previous mode of transportation]" in other words “energy density wins the day".* That was running through my head when I read they were switching to technology with lower energy density but, to your point and to the article's point, it’s really about systems level energy density and not cell level energy density. * with Tesla we have now seen that there is another factor, convenience, that my professor did not account for. I own a Tesla and the primary selling point… OK it was acceleration… But the secondary selling point was never having to go to a gas station again when I am just barely going to make the meeting and forgot to fill my gas tank the night before.

deleted 5y ago
[deleted]
cinntaile 5y ago
He said that before we had EVs I presume.
- MrDunham 5y ago
  Before we had good EVs (If I remember right electric vehicles at the time had something like 60 miles of range... I might be off, though. That was about 14 years ago)
dnautics 5y ago
Exactly how many data points did he have in this thesis? Running, horse, bike, car, train (coal, electric, diesel), plane? There's lots of places which have flip flopped, e.g. Italy going from train -> Alitalia -> high speed rail
- onion2k 5y ago
  Wouldn't it be more like running, horse, better horse because of improved diet, better horse because of improved medicine, bike, better bike because of gears, better bike because of better gears, car, better car because of better fuel, better car because of better fuel, better car because of better fuel, better car because of better fuel, better car because of better fuel, better car because of better fuel...
  - fullstop 5y ago
    At some point economical aspects are also important. If fuel was available for gas engines but it was rare, it doesn't matter how energy-dense it is if it's expensive.
    - dnautics 5y ago
      yep. The Soyuz was supposed to run on Syntin but then they reverted back because the added energy density and payload capacity (something like 30%) was not worth the manufacturing cost. https://en.wikipedia.org/wiki/Syntin https://en.wikipedia.org/wiki/Syntin Edit: Soyuz U2 (Syntin version) launched 72!! rockets. Then they reverted back.
api 5y ago
Energy density must be calculated from useful energy (work) after conversion loss. By that metric gas burned in an ICE is not much better than lithium batteries. The latter store less energy but it’s extraction is over 90% efficient. Most of the energy you buy with a tank of gas goes to heat the air around and behind the car as you drive.
- andruby 5y ago
  The weight of a full gas tank that can drive you 1000km is a lot less than the weight of batteries that can do the same. even if you include the ICE engine. In other words: even when you take conversion into account, energy density (both by weight and volume) is better in gasoline than battery. (I love BEV, and I see it will win over most of the market, but gas wins on energy density)
jjav 5y ago
> But the secondary selling point was never having to go to a gas station again when I am just barely going to make the meeting and forgot to fill my gas tank the night before. Curious example since that's one of the drawbacks of an EV. If you forgot to fill the gas tank and have to stop, you'll be 5 minutes late. But if you forgot to charge the EV, now you're looking at several hours late (or give up and call a cab).
- MrDunham 5y ago
  So I have actually been in (close to) this situation. i’ll address a couple of things though… First, since you plug-in every day at home it is very very rare for me to forget. Second, the total available range is still close to my old gas cars which means I need to have forgotten for many days in a row which in the last nine months has never happened. BUT, I did say that I was low on energy on a day I needed to make a long drive… Backstory was I was intentionally draining my battery over a period of about a week without charging (trying to recalibrate the gauges... very rare to do). In the morning on a day I needed to make a three hour round-trip drive I realized I was at 20% power. So I hightailed it to the nearest Tesla supercharger, plugged in, pulled out my laptop (I'm sitting on a giant battery... powering a MacBook is no issue) to get some work done, and 20 minutes later I was at 80% (enough for 200 miles - or my entire round trip). So the power issue was caused semi-intentionally and entirely my fault but also it took very little time to solve it. It would be a bigger issue for somebody who isn’t near a supercharger (and no 220 line at home as they'll go 0->full overnight) but again it is very very easy to remember to plug-in at night and many/most people would generally need to forget to charge for at least three or four days before it becomes an issue.
  - jjav 5y ago
    > Second, the total available range is still close to my old gas cars If the range is so huge, I see it might not be an issue. We have a Fiat 500e, so forgetting to charge overnight (or if the timer didn't go on as intended for whatever reason) means a guaranteed crisis in the morning as there's no way to get to work.

deleted 5y ago

[deleted]

cinntaile 5y ago

He said that before we had EVs I presume.

MrDunham 5y ago
Before we had good EVs (If I remember right electric vehicles at the time had something like 60 miles of range... I might be off, though. That was about 14 years ago)

dnautics 5y ago

Exactly how many data points did he have in this thesis? Running, horse, bike, car, train (coal, electric, diesel), plane? There's lots of places which have flip flopped, e.g. Italy going from train -> Alitalia -> high speed rail

onion2k 5y ago
Wouldn't it be more like running, horse, better horse because of improved diet, better horse because of improved medicine, bike, better bike because of gears, better bike because of better gears, car, better car because of better fuel, better car because of better fuel, better car because of better fuel, better car because of better fuel, better car because of better fuel, better car because of better fuel...
- fullstop 5y ago
  At some point economical aspects are also important. If fuel was available for gas engines but it was rare, it doesn't matter how energy-dense it is if it's expensive.
  - dnautics 5y ago
    yep. The Soyuz was supposed to run on Syntin but then they reverted back because the added energy density and payload capacity (something like 30%) was not worth the manufacturing cost. https://en.wikipedia.org/wiki/Syntin https://en.wikipedia.org/wiki/Syntin Edit: Soyuz U2 (Syntin version) launched 72!! rockets. Then they reverted back.

api 5y ago

Energy density must be calculated from useful energy (work) after conversion loss. By that metric gas burned in an ICE is not much better than lithium batteries. The latter store less energy but it’s extraction is over 90% efficient. Most of the energy you buy with a tank of gas goes to heat the air around and behind the car as you drive.

andruby 5y ago
The weight of a full gas tank that can drive you 1000km is a lot less than the weight of batteries that can do the same. even if you include the ICE engine. In other words: even when you take conversion into account, energy density (both by weight and volume) is better in gasoline than battery. (I love BEV, and I see it will win over most of the market, but gas wins on energy density)

jjav 5y ago

> But the secondary selling point was never having to go to a gas station again when I am just barely going to make the meeting and forgot to fill my gas tank the night before. Curious example since that's one of the drawbacks of an EV. If you forgot to fill the gas tank and have to stop, you'll be 5 minutes late. But if you forgot to charge the EV, now you're looking at several hours late (or give up and call a cab).

MrDunham 5y ago
So I have actually been in (close to) this situation. i’ll address a couple of things though… First, since you plug-in every day at home it is very very rare for me to forget. Second, the total available range is still close to my old gas cars which means I need to have forgotten for many days in a row which in the last nine months has never happened. BUT, I did say that I was low on energy on a day I needed to make a long drive… Backstory was I was intentionally draining my battery over a period of about a week without charging (trying to recalibrate the gauges... very rare to do). In the morning on a day I needed to make a three hour round-trip drive I realized I was at 20% power. So I hightailed it to the nearest Tesla supercharger, plugged in, pulled out my laptop (I'm sitting on a giant battery... powering a MacBook is no issue) to get some work done, and 20 minutes later I was at 80% (enough for 200 miles - or my entire round trip). So the power issue was caused semi-intentionally and entirely my fault but also it took very little time to solve it. It would be a bigger issue for somebody who isn’t near a supercharger (and no 220 line at home as they'll go 0->full overnight) but again it is very very easy to remember to plug-in at night and many/most people would generally need to forget to charge for at least three or four days before it becomes an issue.
- jjav 5y ago
  > Second, the total available range is still close to my old gas cars If the range is so huge, I see it might not be an issue. We have a Fiat 500e, so forgetting to charge overnight (or if the timer didn't go on as intended for whatever reason) means a guaranteed crisis in the morning as there's no way to get to work.