4 ms·

Neat. One thing that isn't addressed however is the sustainability of the energy source. Until we have electric airplanes, trains will continue to have a lower

by kepano 11y ago

Neat. One thing that isn't addressed however is the sustainability of the energy source. Until we have electric airplanes, trains will continue to have a lower carbon footprint.

etep 11y ago
It isn't clear that electric is a lower carbon footprint, right? What if the electricity is generated at a coal plant? Intuitively the train should be more efficient, right? So the question imo is why does the data say otherwise: Is there less market pressure to make efficient trains? Is this data wrong? Is this intuition wrong? (edit to include questioning the intuition itself, i.e. based on the reply comment)
- msandford 11y ago
  Everything else equal I agree, but everything else is not equal. The FRA says that all passenger trains have to be built crazy heavy duty in case of derailments. To the substantial detriment of fuel economy.
  - deleted 11y ago
    [deleted]
  - etep 11y ago
    Thank you. I didn't know about that requirement; and it would obviously be ridiculous to stipulate that airframes be made heavy.
    - jzwinck 11y ago
      Planes are made heavy, for the same reasons as trains: safety enhancement and cost reduction. Ever notice how every wheelie cart on a plane has not one but two locking handles to secure it? How about the ram air turbine [1] which is used almost never but weighs hundreds of pounds? Seat frames are still made mostly of metal, whereas if weight were the only consideration they would probably be carbon fiber. [1] https://en.wikipedia.org/wiki/Ram_air_turbine https://en.wikipedia.org/wiki/Ram_air_turbine
      - etep 11y ago
        Yes, I would not dispute your statement, but that does not contradict the fact that airframe weight is minimized to increase efficiency. I did notice the seats were mostly metal, but I also noticed their (essentially) honeycombed design: they are mostly the rigid frame, rather than solid metal. I'm sure if they could reasonably remove the ram air turbine, they absolutely would (both for cost and efficiency).
    - sabj 11y ago
      One reason for these tough requirements is that a very large portion of U.S. passenger rail routes go over track owned (and used) by freight rail companies. Therefore, passenger train collisions and other such risks are weighed not only against other passenger trains, but also heavier freight trains. This is one reason why U.S. trains have (relatively) 'harsher' requirements than other countries where track is not shared to such a high extent. Separately, this degree of track-sharing is one of the reasons why average passenger rail journey speed has decreased in many places over a 100-year time period! Obviously, in both cases, there are many many factors involved - but, an important element.
- kepano 11y ago
  Obviously electricity doesn't necessarily come from a clean source, but it at least has the potential to.
- Zardoz84 11y ago
  It's the same pitfall that Hydrogen powered vehicles. Yeah they clean, but everybody forgot form where we get the hidrogen. You need to use electric energy to get it from water or get it from hydrocarbon fuels. How ever, moving all to electric powered, at least allow us to replace a single thing (electric generation stations) to something more clean, like a mix of solar/wind/geo/hydro power sources + nuclear)
ars 11y ago
> One thing that isn't addressed however is the sustainability of the energy source. You can make hydrocarbon fuel for airplanes if you have electrical power. There is no risk of running out, you can make it literally from thin air! All the atoms necessary are in air (although obviously there are easier sources). On top of that we could save our oil for airplanes and use other fuels for land vehicles - doing that we'd have effectively unlimited amounts. > Until we have electric airplanes, trains will continue to have a lower carbon footprint. Being electrical does not automatically mean less CO2. I'm not following your logic.
icanhackit 11y ago
Until we have electric airplanes While I believe battery-powered cars like the Tesla S make more sense than hydrogen/fuel-cell based cars, perhaps fuel cells make sense in airplanes. For cars, the weight of batteries are an advantage as they provide down-force and can be readily charged by virtue of being close the ground where there's infrastructure, in stark contrast to flying at 36,000ft where infrastructure is non-existent. Addendum: The infrastructure issues that come with fuel-cell distribution and refueling would be eliminated thanks to the centralized nature of airports.
- kepano 11y ago
  Good point, but we don't have commercial fuel-cell planes either. Swap "electric" with "clean fuel".
- danielbarla 11y ago
  I've seen a number of back of the napkin calculations involving electric airplanes, but even when compared with fuel cells, traditionally fuelled airplanes have the advantage that their weight greatly decreases as they use fuel. Apparently a significant portion of the range of an airplane comes from when the tanks have < 50% fuel. This shifts the economics even further in their favour, aside from simple energy density calculations (as you're lugging the now useless, yet still very heavy batteries / fuel cells all the way to the destination). While I'd love to see a shift in a more sustainable direction, I wonder if we're going to be close to that anytime soon.
- thedrbrian 11y ago
  On the other hand weight is the enemy of everything good in cars. Weight makes them worse , use more energy to move accelerate slower.
Zardoz84 11y ago
We have electric planes. How ever we have a problem of energy storage/generation density that actually make unviable beyond drones and experimental planes that don't carry cargo.

by kepano 11y ago

Neat. One thing that isn't addressed however is the sustainability of the energy source. Until we have electric airplanes, trains will continue to have a lower carbon footprint.

etep 11y ago

It isn't clear that electric is a lower carbon footprint, right? What if the electricity is generated at a coal plant? Intuitively the train should be more efficient, right? So the question imo is why does the data say otherwise: Is there less market pressure to make efficient trains? Is this data wrong? Is this intuition wrong? (edit to include questioning the intuition itself, i.e. based on the reply comment)

msandford 11y ago
Everything else equal I agree, but everything else is not equal. The FRA says that all passenger trains have to be built crazy heavy duty in case of derailments. To the substantial detriment of fuel economy.
- deleted 11y ago
  [deleted]
- etep 11y ago
  Thank you. I didn't know about that requirement; and it would obviously be ridiculous to stipulate that airframes be made heavy.
  - jzwinck 11y ago
    Planes are made heavy, for the same reasons as trains: safety enhancement and cost reduction. Ever notice how every wheelie cart on a plane has not one but two locking handles to secure it? How about the ram air turbine [1] which is used almost never but weighs hundreds of pounds? Seat frames are still made mostly of metal, whereas if weight were the only consideration they would probably be carbon fiber. [1] https://en.wikipedia.org/wiki/Ram_air_turbine https://en.wikipedia.org/wiki/Ram_air_turbine
    - etep 11y ago
      Yes, I would not dispute your statement, but that does not contradict the fact that airframe weight is minimized to increase efficiency. I did notice the seats were mostly metal, but I also noticed their (essentially) honeycombed design: they are mostly the rigid frame, rather than solid metal. I'm sure if they could reasonably remove the ram air turbine, they absolutely would (both for cost and efficiency).
  - sabj 11y ago
    One reason for these tough requirements is that a very large portion of U.S. passenger rail routes go over track owned (and used) by freight rail companies. Therefore, passenger train collisions and other such risks are weighed not only against other passenger trains, but also heavier freight trains. This is one reason why U.S. trains have (relatively) 'harsher' requirements than other countries where track is not shared to such a high extent. Separately, this degree of track-sharing is one of the reasons why average passenger rail journey speed has decreased in many places over a 100-year time period! Obviously, in both cases, there are many many factors involved - but, an important element.
kepano 11y ago
Obviously electricity doesn't necessarily come from a clean source, but it at least has the potential to.
Zardoz84 11y ago
It's the same pitfall that Hydrogen powered vehicles. Yeah they clean, but everybody forgot form where we get the hidrogen. You need to use electric energy to get it from water or get it from hydrocarbon fuels. How ever, moving all to electric powered, at least allow us to replace a single thing (electric generation stations) to something more clean, like a mix of solar/wind/geo/hydro power sources + nuclear)

ars 11y ago

> One thing that isn't addressed however is the sustainability of the energy source. You can make hydrocarbon fuel for airplanes if you have electrical power. There is no risk of running out, you can make it literally from thin air! All the atoms necessary are in air (although obviously there are easier sources). On top of that we could save our oil for airplanes and use other fuels for land vehicles - doing that we'd have effectively unlimited amounts. > Until we have electric airplanes, trains will continue to have a lower carbon footprint. Being electrical does not automatically mean less CO2. I'm not following your logic.

icanhackit 11y ago

Until we have electric airplanes While I believe battery-powered cars like the Tesla S make more sense than hydrogen/fuel-cell based cars, perhaps fuel cells make sense in airplanes. For cars, the weight of batteries are an advantage as they provide down-force and can be readily charged by virtue of being close the ground where there's infrastructure, in stark contrast to flying at 36,000ft where infrastructure is non-existent. Addendum: The infrastructure issues that come with fuel-cell distribution and refueling would be eliminated thanks to the centralized nature of airports.

kepano 11y ago
Good point, but we don't have commercial fuel-cell planes either. Swap "electric" with "clean fuel".
danielbarla 11y ago
I've seen a number of back of the napkin calculations involving electric airplanes, but even when compared with fuel cells, traditionally fuelled airplanes have the advantage that their weight greatly decreases as they use fuel. Apparently a significant portion of the range of an airplane comes from when the tanks have < 50% fuel. This shifts the economics even further in their favour, aside from simple energy density calculations (as you're lugging the now useless, yet still very heavy batteries / fuel cells all the way to the destination). While I'd love to see a shift in a more sustainable direction, I wonder if we're going to be close to that anytime soon.
thedrbrian 11y ago
On the other hand weight is the enemy of everything good in cars. Weight makes them worse , use more energy to move accelerate slower.

Zardoz84 11y ago

We have electric planes. How ever we have a problem of energy storage/generation density that actually make unviable beyond drones and experimental planes that don't carry cargo.