7 ms·

As an example: transportation. More specifically, airplanes. Energy density is a bigger factor for some uses than others.

_aavaa_ 3y ago
Anything but the longest flights will end up electric, and everything else can go biofuels. No need for a hydrogen-centered Rube Goldberg machine. And if biofuels cost is a concern, synthetic fuels will be out of the question.
- goethes_kind 3y ago
  You are betting on a 20x improvement in mass energy density of batteries for that to become realistic. That would probably require entirely new chemistries and while I am not going to rule it out, there is really no good reason to believe that it will happen either. Hydrogen powered flight is on the other hand only a matter of incremental improvements. It is already feasible today.
  - _aavaa_ 3y ago
    Damn straight I am: https://www.energy.gov/eere/vehicles/articles/fotw-1234-april-18-2022-volumetric-energy-density-lithium-ion-batteries https://www.energy.gov/eere/vehicles/articles/fotw-1234-apri... Ain’t no incremental improvement going to improve the density of a gas or a liquid. On top of that you talk of energy per mass, but what kills you for flights is also volume. Hydrogen power flights are not feasible today. Even hydrogen busses are struggling to operate, to say. I thing of trains. For starters you’ll need hydrogen at any and all possible destinations (plus any nearby airports if you’re diverted) since nobody is going to buy a plane that will likely get stranded. Then: 1. Hydrogen’s energy/volume is far too low. 2. You can’t store it in the empty space in the fuselage due to pressure vessel geometry requirements. 3. You need heaters and coolers and all sorts of extra parts to operate something hydrogen power (hint: a hydrogen car is just an electric car with a small battery and a while separate hydrogen system frankesteined ontop). 4. Going back to that volume, you’ll need to store the hydeogren tanks inside the main fuselage, where the volume required is going to either eat into your available volume for cabin or cargo. OR, you’re gonna need a bigger cross-section, which will increase your drag. To top all that off. Nobody is using green hydrogen. They’re using hydrogen made directly from methane (or god help us coal). This hydrogen has more GhG emissions associate with it than the methane it’s made from. Hydrogen itself also has a GHG impact since it will interfere with the processes occurring that remove other GHGs.
    - goethes_kind 3y ago
      The bottom line is, the batteries that you would need do not exist yet. You just have faith that your extrapolation holds true. I cannot comment on that either way, because there is no way to tell when battery energy densities will stop improving. Synthetic kerosene is a technology that we have today and imho the most likely option because it is plug and play. Otherwise one would have to work out many modifications to fly directly on hydrogen, but that is also technically possible today, if one wanted to do it that way.
      - _aavaa_ 3y ago
        There is no way to know when it stops, but looking at the historical trend it isn’t slowly down yet. The technology for synthetic karosene is something we have today, expect it cost more 10x regular karosene and: A) what’s the path to scale to bring that number down? Who isn’t going to pay that 10x price while it’s that high. Batteries had cell phones, then laptop, then cars and storage. Now it’s trucks, ships and planes are next up. B) by continuing with combustions engines you keep the same operating costs that you have now. Whereas electrification gets rid of many of them (same way it did for cars).
    - _hypx 3y ago
      > Damn straight I am: https://www.energy.gov/eere/vehicles/articles/fotw-1234-april-18-2022-volumetric-energy-density-lithium-ion-batteries https://www.energy.gov/eere/vehicles/articles/fotw-1234-apri... Seriously, that claim is just bullshit. 55 Wh/L is worse than a lead-acid battery. That graph is straight-up lying.
      - _aavaa_ 3y ago
        That number is for the battery pack as a whole, not just the lithium ion cell.
        _hypx 3y ago
        And how did they fail so badly as to get a li-ion battery pack with worse energy density than lead-acid batteries? I'm sorry, but that is simply far too ridiculous to be taken seriously. It's blatantly some made-up number that no one can believe.
  - theshrike79 3y ago
    The biggest advantage of electric flight is the maintenance interval. Electric engines need next to no maintenance. Jet engines need to be maintained pretty much after every flight and that costs $$.
- ianburrell 3y ago
  Any commercial flights over 500mi will be too far for electric. There are a lot of regional flights that might work as electric.
  - _aavaa_ 3y ago
    There will be some X mi limit that will slowly increase. But the energy source that handles everything beyond that is much more likely to be biolfuels than hydrogen (or synthetics). The cost it much better and the infrastructure is already there.
- allannienhuis 3y ago
  the question I'm replying to was about why the need for fuels at all, not specifically Hydrogen. I'm not big on hydrogen. I like the ideas around ammonia based fuels. Biofuels have other environmental costs that concern some people. Synthetic fuels could serve a purpose, but yes energy cost has to be really low for that to make sense. But they might be the only viable option in some cases. Obviously costs change the demand side of the equation - it may be that we wind up with very expensive airfare, and have a lot more somewhat slower modes (say high-speed rail) that can more easily use the cheaper energy forms.
  - _aavaa_ 3y ago
    Ammonia based fuels are only pushed by people who don’t have to work with ammonia. It’s being pushed for ships. If anyone is insane enough to try it, there will be a lot of blood on their hands after the first accident. That biofuels have costs that concern people is letting perfect be the enemy of the good. Any of the synthetic fuels or hydrogen options require an incredible amount of energy. Energy that could have been available to decarbonize the grid, or energy that could have been used for making clean water or any other pressing issues. The thing is, those costs are more hidden.
ianburrell 3y ago
Another good example is cargo ships. Making those electric would be expensive and use a lot of cargo space. Hydrogen is lower density than bunker fuel but better than batteries. It should be possible to retrofit hydrogen engines to existing ships unlike using kites.
- _aavaa_ 3y ago
  Bunker fuel is used because companies basically have to pay to get rid of it. It’s 3.5% sufur for crying out loud. The idea that the shipping companies would pay for a premium gas like hydrogen is laughable. Even with bunker fuel, fuel costs make up a large percentage of shipping cost. There’s no way that’s happening.
- uncertainrhymes 3y ago
  I don't have first-hand knowledge of this, but my understanding is most cargo ships already have electric engines to drive the propellers. The fuel is only there to run the generators. Fuel aside, might be less of a retrofit than we think.
  - Gwypaas 3y ago
    Not true. They use hyper optimized two stroke diesel engines. Cruise ships, RORO, off-shore supply ships and vessels with similarly dynamic operating profiles have started to use diesel electric. Also starting to employ batteries to handle peak loads.
JumpCrisscross 3y ago
> an example: transportation. More specifically, airplanes Biology found an efficient solution to storing energy with hydrogen, and its hydrocarbons. I struggle to imagine why hydrogen-powered planes are superior other than on marketing merits.
- _hypx 3y ago
  That would be synfuels, aka e-fuels or SAF. The problem is that you need to make it in a carbon-neutral way. While this is not impossible, it is currently hard and quite expensive.
  - _aavaa_ 3y ago
    Synfuels are not the only option. We can continue letting nature do the hard part and use biofuels.
    - _hypx 3y ago
      You should read recent threads on ethanol here. That is almost certainly not a option.
      - _aavaa_ 3y ago
        I don't see the thread you're referring you.
        _hypx 3y ago
        There are several posts about ethanol recently on ycombinator. I did not participate in them. But if you read them, you'll find out that anything based on biofuels is pure greenwashing and not serious environmental policy.
        _aavaa_ 3y ago
        Corn based biofuels have problems yes. But they are not all of biofuels. The only pure greenwashing is hydrogen push by fossil fuel companies who wish to continue having something to do with their methane. See Germany recently with their “hydrogen-ready” boilers.

_aavaa_ 3y ago

Anything but the longest flights will end up electric, and everything else can go biofuels. No need for a hydrogen-centered Rube Goldberg machine. And if biofuels cost is a concern, synthetic fuels will be out of the question.

goethes_kind 3y ago
You are betting on a 20x improvement in mass energy density of batteries for that to become realistic. That would probably require entirely new chemistries and while I am not going to rule it out, there is really no good reason to believe that it will happen either. Hydrogen powered flight is on the other hand only a matter of incremental improvements. It is already feasible today.
- _aavaa_ 3y ago
  Damn straight I am: https://www.energy.gov/eere/vehicles/articles/fotw-1234-april-18-2022-volumetric-energy-density-lithium-ion-batteries https://www.energy.gov/eere/vehicles/articles/fotw-1234-apri... Ain’t no incremental improvement going to improve the density of a gas or a liquid. On top of that you talk of energy per mass, but what kills you for flights is also volume. Hydrogen power flights are not feasible today. Even hydrogen busses are struggling to operate, to say. I thing of trains. For starters you’ll need hydrogen at any and all possible destinations (plus any nearby airports if you’re diverted) since nobody is going to buy a plane that will likely get stranded. Then: 1. Hydrogen’s energy/volume is far too low. 2. You can’t store it in the empty space in the fuselage due to pressure vessel geometry requirements. 3. You need heaters and coolers and all sorts of extra parts to operate something hydrogen power (hint: a hydrogen car is just an electric car with a small battery and a while separate hydrogen system frankesteined ontop). 4. Going back to that volume, you’ll need to store the hydeogren tanks inside the main fuselage, where the volume required is going to either eat into your available volume for cabin or cargo. OR, you’re gonna need a bigger cross-section, which will increase your drag. To top all that off. Nobody is using green hydrogen. They’re using hydrogen made directly from methane (or god help us coal). This hydrogen has more GhG emissions associate with it than the methane it’s made from. Hydrogen itself also has a GHG impact since it will interfere with the processes occurring that remove other GHGs.
  - goethes_kind 3y ago
    The bottom line is, the batteries that you would need do not exist yet. You just have faith that your extrapolation holds true. I cannot comment on that either way, because there is no way to tell when battery energy densities will stop improving. Synthetic kerosene is a technology that we have today and imho the most likely option because it is plug and play. Otherwise one would have to work out many modifications to fly directly on hydrogen, but that is also technically possible today, if one wanted to do it that way.
    - _aavaa_ 3y ago
      There is no way to know when it stops, but looking at the historical trend it isn’t slowly down yet. The technology for synthetic karosene is something we have today, expect it cost more 10x regular karosene and: A) what’s the path to scale to bring that number down? Who isn’t going to pay that 10x price while it’s that high. Batteries had cell phones, then laptop, then cars and storage. Now it’s trucks, ships and planes are next up. B) by continuing with combustions engines you keep the same operating costs that you have now. Whereas electrification gets rid of many of them (same way it did for cars).
  - _hypx 3y ago
    > Damn straight I am: https://www.energy.gov/eere/vehicles/articles/fotw-1234-april-18-2022-volumetric-energy-density-lithium-ion-batteries https://www.energy.gov/eere/vehicles/articles/fotw-1234-apri... Seriously, that claim is just bullshit. 55 Wh/L is worse than a lead-acid battery. That graph is straight-up lying.
    - _aavaa_ 3y ago
      That number is for the battery pack as a whole, not just the lithium ion cell.
      - _hypx 3y ago
        And how did they fail so badly as to get a li-ion battery pack with worse energy density than lead-acid batteries? I'm sorry, but that is simply far too ridiculous to be taken seriously. It's blatantly some made-up number that no one can believe.
- theshrike79 3y ago
  The biggest advantage of electric flight is the maintenance interval. Electric engines need next to no maintenance. Jet engines need to be maintained pretty much after every flight and that costs $$.
ianburrell 3y ago
Any commercial flights over 500mi will be too far for electric. There are a lot of regional flights that might work as electric.
- _aavaa_ 3y ago
  There will be some X mi limit that will slowly increase. But the energy source that handles everything beyond that is much more likely to be biolfuels than hydrogen (or synthetics). The cost it much better and the infrastructure is already there.
allannienhuis 3y ago
the question I'm replying to was about why the need for fuels at all, not specifically Hydrogen. I'm not big on hydrogen. I like the ideas around ammonia based fuels. Biofuels have other environmental costs that concern some people. Synthetic fuels could serve a purpose, but yes energy cost has to be really low for that to make sense. But they might be the only viable option in some cases. Obviously costs change the demand side of the equation - it may be that we wind up with very expensive airfare, and have a lot more somewhat slower modes (say high-speed rail) that can more easily use the cheaper energy forms.
- _aavaa_ 3y ago
  Ammonia based fuels are only pushed by people who don’t have to work with ammonia. It’s being pushed for ships. If anyone is insane enough to try it, there will be a lot of blood on their hands after the first accident. That biofuels have costs that concern people is letting perfect be the enemy of the good. Any of the synthetic fuels or hydrogen options require an incredible amount of energy. Energy that could have been available to decarbonize the grid, or energy that could have been used for making clean water or any other pressing issues. The thing is, those costs are more hidden.

ianburrell 3y ago

Another good example is cargo ships. Making those electric would be expensive and use a lot of cargo space. Hydrogen is lower density than bunker fuel but better than batteries. It should be possible to retrofit hydrogen engines to existing ships unlike using kites.

_aavaa_ 3y ago
Bunker fuel is used because companies basically have to pay to get rid of it. It’s 3.5% sufur for crying out loud. The idea that the shipping companies would pay for a premium gas like hydrogen is laughable. Even with bunker fuel, fuel costs make up a large percentage of shipping cost. There’s no way that’s happening.
uncertainrhymes 3y ago
I don't have first-hand knowledge of this, but my understanding is most cargo ships already have electric engines to drive the propellers. The fuel is only there to run the generators. Fuel aside, might be less of a retrofit than we think.
- Gwypaas 3y ago
  Not true. They use hyper optimized two stroke diesel engines. Cruise ships, RORO, off-shore supply ships and vessels with similarly dynamic operating profiles have started to use diesel electric. Also starting to employ batteries to handle peak loads.

JumpCrisscross 3y ago

> an example: transportation. More specifically, airplanes Biology found an efficient solution to storing energy with hydrogen, and its hydrocarbons. I struggle to imagine why hydrogen-powered planes are superior other than on marketing merits.

_hypx 3y ago
That would be synfuels, aka e-fuels or SAF. The problem is that you need to make it in a carbon-neutral way. While this is not impossible, it is currently hard and quite expensive.
- _aavaa_ 3y ago
  Synfuels are not the only option. We can continue letting nature do the hard part and use biofuels.
  - _hypx 3y ago
    You should read recent threads on ethanol here. That is almost certainly not a option.
    - _aavaa_ 3y ago
      I don't see the thread you're referring you.
      - _hypx 3y ago
        There are several posts about ethanol recently on ycombinator. I did not participate in them. But if you read them, you'll find out that anything based on biofuels is pure greenwashing and not serious environmental policy.
        _aavaa_ 3y ago
        Corn based biofuels have problems yes. But they are not all of biofuels. The only pure greenwashing is hydrogen push by fossil fuel companies who wish to continue having something to do with their methane. See Germany recently with their “hydrogen-ready” boilers.