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Hydrogen storage may have always been a problem, but it has never been the problem. Efficiency of conversion is. Until someone either comes up with a much bette

Hydrogen storage may have always been a problem, but it has never been the problem. Efficiency of conversion is. Until someone either comes up with a much better way to generate hydrogen or lithium becomes a thousand times more expensive, BEVs are superior to hydrogen vehicles and they're getting more superior every day. https://i.imgur.com/4YQfNgQ.jpg https://i.imgur.com/4YQfNgQ.jpg

tener 5y ago
Great graph. The proposed tech is aiming to replace non critical part which is already 90% efficient, but takes extra volume in the car.
- upofadown 5y ago
  Compression/liquefaction doesn't really have an efficiency. It is just a dead loss of energy. So you really need to know the assumptions to know what the 90%/65% is of. I suspect it is the same for the other percentages thrown around on that diagram. ... and why doesn't the H2 vehicle do regenerative braking?
  - shaded-enmity 5y ago
    Probably because you'd need a battery to store the energy generated via braking thus eliminating much of the environmental benefit.
  - SigmundA 5y ago
    Any loss means efficiency below 100%. If it takes 1kwh of electricity to compress 10 kWh of hydrogen (assuming 100% conversion back into electricity in the fuel cell, which its not) then your efficiency is 90%. This is applied to all steps, electrolysis, compression, transport, and fuel cell conversion back to electricity. Current fuel cells cannot put out enough burst power to acceleration nor can they accept electricity in reverse to generate hydrogen so all current fuel cell vehicles use a traction battery that is charged by the fuel cell, they are basically series hybrids. They also typically have lower acceleration because the small traction battery + fuel cell cannot supply as much power as a much larger full EV battery.
  - tener 5y ago
    Regenerative braking works for electric cars because it is super easy to convert movement into electric energy. This isn't true for most other sources of energy H2 and petrol included. Reversing combustion is kind of hard and takes up big chunk of the linked graph.
    - Gibbon1 5y ago
      Fuel cells are crappy in that the reaction isn't reversible. Where Batteries and electric motors are nearly fully reversible. And fuel cells are only efficient when compared to heat engines. But subpar when compared to batteries.
Youden 5y ago
There are criteria other than efficiency though. What's the environmenal impact of a hydrogen fuel cell versus a rechargeable battery with a comparable range? Doesn't making a battery require mining a ton of metals? How efficient is the recycling of spent batteries? And on the other hand, how long does a hydrogen fuel cell last?
- SECProto 5y ago
  > What's the environmenal impact of a hydrogen fuel cell versus a rechargeable battery with a comparable range? Battery-electric vehicles are about 2-3 times more energy efficient than hydrogen fuel cell vehicles, according to VW [0] > Doesn't making a battery require mining a ton of metals? Less, actually - a bit under half a tonne of metal in a Tesla battery pack, most of it nickle (as of 5 years ago) [1] > How efficient is the recycling of spent batteries? Roughly 92% [2] and improving. A car purchased today would have its battery recycled in ~10 years, so it'll be higher by then. [0] https://insideevs.com/news/406676/battery-electric-hydrogen-fuel-cell-efficiency-comparison/ https://insideevs.com/news/406676/battery-electric-hydrogen-... [1] https://electrek.co/2016/11/01/breakdown-raw-materials-tesla-batteries-possible-bottleneck/ https://electrek.co/2016/11/01/breakdown-raw-materials-tesla... [2] https://electrek.co/2021/08/09/tesla-battery-cell-material-recovery-new-recycling-process/ https://electrek.co/2021/08/09/tesla-battery-cell-material-r...
  - Youden 5y ago
    My point was that the environmental impact encompasses more than just the energy usage. What I wanted to get at with my questions was "what's the ratio of bad stuff produced per kilometer driven for hydrogen and for batteries?" How much more mining is needed to produce a battery pack than a fuel cell? How much more waste metal is there? Are there any chemical pollutants in either system? Both systems are going to have different ratios between Bad Stuff and efficiency and my unqualified guess is that hydrogen _might_ be better.
    - SECProto 5y ago
      > What I wanted to get at with my questions was "what's the ratio of bad stuff produced per kilometer driven for hydrogen and for batteries?" Right. When comparing objects of similar complexity, cost of the object is generally pretty proportional to bad-stuff-produced, with exceptions for unpriced externalities (carbon emissions being a big one, and mining or refining in low-responsibility jurisdictions being another). The carbon emissions of battery pack manufacturing are small[1] relative to lifetime emissions from an ICE car, not totally sure for FCEV. > Both systems are going to have different ratios between Bad Stuff and efficiency and my unqualified guess is that hydrogen _might_ be better. I couldn't find anything specific to FCEV, but my gut instinct is that FCEV would be dramatically worse - hydrogen is reformed from natural gas, necessarily entailing carbon emissions. If you're going to release the CO2 from natural gas anyway, might as well do it by burning in a high-efficiency turbine and use the energy to charge your BEV at high end-to-end efficiency. Or if you're going to consider "green" hydrogen, might as well use the renewable energy to directly charge a battery, at 3x higher efficiency. [1] https://theicct.org/sites/default/files/publications/EV-life-cycle-GHG_ICCT-Briefing_09022018_vF.pdf https://theicct.org/sites/default/files/publications/EV-life...
xorcist 5y ago
But storage is the main problem with efficiency. The fuel cell itself is pretty efficient. (The linked article offers very little actual information on the efficiency of these discs however, which isn't a good sign.)
- SigmundA 5y ago
  Current fuels cells like in the Mirai have a peak efficiency of around 65% all the way down to around 40% at full power. A lithium battery is nearly 100% efficient. They both run through an inverter and electric motor so those efficiencies are the same.
  - modshatereality 5y ago
    100% efficient? their capabilities degrade over time, and they are basically toxic waste when they are to be disposed of.
    - SigmundA 5y ago
      Their capacity diminishes not their efficiency and they are 80-90% recyclable. Efficiency is how much power is put in vs how much you get out.
  - xorcist 5y ago
    Well, of course. If you have a battery, then use the battery. Many practical uses keep a complementary battery for extra capacity for this reason. But the use cases are different. A fuel cell is efficient compared to pretty much every other form of generating electricity from energy stored in a fuel that we know of.
    - SigmundA 5y ago
      The point is if you have electricity then converting to hydrogen, compressing transporting and turning back into electricity in a fuel cell is much less efficient than just charging a battery. Why would you do that? You could argue energy density, but looking at current fuel cell vehicles like the Mirai shows the have only a slim advantage in range dues to the weight of the fuel cells, high pressure tanks and tractions batteries and extra structure to protect the tanks.
darksaints 5y ago
Efficiency has never been the problem. Cost has always been the driving factor behind technology adoption, and the highest efficiency solutions are rarely the cheapest. BEVs are winning at the momemy not because they're efficient, but because the cost/benefit is finally coming out ahead due to advances in battery technology. But BEVs don't fully cover all use cases. It is telling that the first commercial truck manufacturer to release a full electric truck has also invested billions into hydrogen. BEVs can certainly handle a lot of usecases, but continuous usage at high power levels isn't one of them, even at theoretical energy densities.
mrfusion 5y ago
What’s the issue with using fuel cells? We just could never get the cost down?
- Tagbert 5y ago
  It takes massive amounts of energy to generate the hydrogen if you split it from water. If you break it out of methane, it also take a lot of energy and secondary product is a lot of CO2. Then it takes more energy to compress the H2. for all that, it’s not clear that there are other significant benefits over batteries for most applications.
- SigmundA 5y ago
  This doesn't replace fuel cells, fuel cells convert hydrogen to electricity, these things store hydrogen for the fuel cells to use. They replace 10,000 psi hydrogen tanks.
toss1 5y ago
Moreover, it is not just the weight budget of storage >>The Plasma Kinetics founder said that his company’s solution weighs only one-third of batteries for the same amount of energy. To compare to battery storage, one needs to compare both the storage and electrical conversion solution, so in this case, is the [weight of the storage cassette] + [weight of fuel cell making electricity] less than [weight of batteries yielding same KWh of electricity]? If they can make that work, they are on to something. I hope they are, but we really need to know the full picture.

tener 5y ago

Great graph. The proposed tech is aiming to replace non critical part which is already 90% efficient, but takes extra volume in the car.

upofadown 5y ago
Compression/liquefaction doesn't really have an efficiency. It is just a dead loss of energy. So you really need to know the assumptions to know what the 90%/65% is of. I suspect it is the same for the other percentages thrown around on that diagram. ... and why doesn't the H2 vehicle do regenerative braking?
- shaded-enmity 5y ago
  Probably because you'd need a battery to store the energy generated via braking thus eliminating much of the environmental benefit.
- SigmundA 5y ago
  Any loss means efficiency below 100%. If it takes 1kwh of electricity to compress 10 kWh of hydrogen (assuming 100% conversion back into electricity in the fuel cell, which its not) then your efficiency is 90%. This is applied to all steps, electrolysis, compression, transport, and fuel cell conversion back to electricity. Current fuel cells cannot put out enough burst power to acceleration nor can they accept electricity in reverse to generate hydrogen so all current fuel cell vehicles use a traction battery that is charged by the fuel cell, they are basically series hybrids. They also typically have lower acceleration because the small traction battery + fuel cell cannot supply as much power as a much larger full EV battery.
- tener 5y ago
  Regenerative braking works for electric cars because it is super easy to convert movement into electric energy. This isn't true for most other sources of energy H2 and petrol included. Reversing combustion is kind of hard and takes up big chunk of the linked graph.
  - Gibbon1 5y ago
    Fuel cells are crappy in that the reaction isn't reversible. Where Batteries and electric motors are nearly fully reversible. And fuel cells are only efficient when compared to heat engines. But subpar when compared to batteries.

Youden 5y ago

There are criteria other than efficiency though. What's the environmenal impact of a hydrogen fuel cell versus a rechargeable battery with a comparable range? Doesn't making a battery require mining a ton of metals? How efficient is the recycling of spent batteries? And on the other hand, how long does a hydrogen fuel cell last?

SECProto 5y ago
> What's the environmenal impact of a hydrogen fuel cell versus a rechargeable battery with a comparable range? Battery-electric vehicles are about 2-3 times more energy efficient than hydrogen fuel cell vehicles, according to VW [0] > Doesn't making a battery require mining a ton of metals? Less, actually - a bit under half a tonne of metal in a Tesla battery pack, most of it nickle (as of 5 years ago) [1] > How efficient is the recycling of spent batteries? Roughly 92% [2] and improving. A car purchased today would have its battery recycled in ~10 years, so it'll be higher by then. [0] https://insideevs.com/news/406676/battery-electric-hydrogen-fuel-cell-efficiency-comparison/ https://insideevs.com/news/406676/battery-electric-hydrogen-... [1] https://electrek.co/2016/11/01/breakdown-raw-materials-tesla-batteries-possible-bottleneck/ https://electrek.co/2016/11/01/breakdown-raw-materials-tesla... [2] https://electrek.co/2021/08/09/tesla-battery-cell-material-recovery-new-recycling-process/ https://electrek.co/2021/08/09/tesla-battery-cell-material-r...
- Youden 5y ago
  My point was that the environmental impact encompasses more than just the energy usage. What I wanted to get at with my questions was "what's the ratio of bad stuff produced per kilometer driven for hydrogen and for batteries?" How much more mining is needed to produce a battery pack than a fuel cell? How much more waste metal is there? Are there any chemical pollutants in either system? Both systems are going to have different ratios between Bad Stuff and efficiency and my unqualified guess is that hydrogen _might_ be better.
  - SECProto 5y ago
    > What I wanted to get at with my questions was "what's the ratio of bad stuff produced per kilometer driven for hydrogen and for batteries?" Right. When comparing objects of similar complexity, cost of the object is generally pretty proportional to bad-stuff-produced, with exceptions for unpriced externalities (carbon emissions being a big one, and mining or refining in low-responsibility jurisdictions being another). The carbon emissions of battery pack manufacturing are small[1] relative to lifetime emissions from an ICE car, not totally sure for FCEV. > Both systems are going to have different ratios between Bad Stuff and efficiency and my unqualified guess is that hydrogen _might_ be better. I couldn't find anything specific to FCEV, but my gut instinct is that FCEV would be dramatically worse - hydrogen is reformed from natural gas, necessarily entailing carbon emissions. If you're going to release the CO2 from natural gas anyway, might as well do it by burning in a high-efficiency turbine and use the energy to charge your BEV at high end-to-end efficiency. Or if you're going to consider "green" hydrogen, might as well use the renewable energy to directly charge a battery, at 3x higher efficiency. [1] https://theicct.org/sites/default/files/publications/EV-life-cycle-GHG_ICCT-Briefing_09022018_vF.pdf https://theicct.org/sites/default/files/publications/EV-life...

xorcist 5y ago

But storage is the main problem with efficiency. The fuel cell itself is pretty efficient. (The linked article offers very little actual information on the efficiency of these discs however, which isn't a good sign.)

SigmundA 5y ago
Current fuels cells like in the Mirai have a peak efficiency of around 65% all the way down to around 40% at full power. A lithium battery is nearly 100% efficient. They both run through an inverter and electric motor so those efficiencies are the same.
- modshatereality 5y ago
  100% efficient? their capabilities degrade over time, and they are basically toxic waste when they are to be disposed of.
  - SigmundA 5y ago
    Their capacity diminishes not their efficiency and they are 80-90% recyclable. Efficiency is how much power is put in vs how much you get out.
- xorcist 5y ago
  Well, of course. If you have a battery, then use the battery. Many practical uses keep a complementary battery for extra capacity for this reason. But the use cases are different. A fuel cell is efficient compared to pretty much every other form of generating electricity from energy stored in a fuel that we know of.
  - SigmundA 5y ago
    The point is if you have electricity then converting to hydrogen, compressing transporting and turning back into electricity in a fuel cell is much less efficient than just charging a battery. Why would you do that? You could argue energy density, but looking at current fuel cell vehicles like the Mirai shows the have only a slim advantage in range dues to the weight of the fuel cells, high pressure tanks and tractions batteries and extra structure to protect the tanks.

darksaints 5y ago

Efficiency has never been the problem. Cost has always been the driving factor behind technology adoption, and the highest efficiency solutions are rarely the cheapest. BEVs are winning at the momemy not because they're efficient, but because the cost/benefit is finally coming out ahead due to advances in battery technology. But BEVs don't fully cover all use cases. It is telling that the first commercial truck manufacturer to release a full electric truck has also invested billions into hydrogen. BEVs can certainly handle a lot of usecases, but continuous usage at high power levels isn't one of them, even at theoretical energy densities.

mrfusion 5y ago

What’s the issue with using fuel cells? We just could never get the cost down?

Tagbert 5y ago
It takes massive amounts of energy to generate the hydrogen if you split it from water. If you break it out of methane, it also take a lot of energy and secondary product is a lot of CO2. Then it takes more energy to compress the H2. for all that, it’s not clear that there are other significant benefits over batteries for most applications.
SigmundA 5y ago
This doesn't replace fuel cells, fuel cells convert hydrogen to electricity, these things store hydrogen for the fuel cells to use. They replace 10,000 psi hydrogen tanks.

toss1 5y ago

Moreover, it is not just the weight budget of storage >>The Plasma Kinetics founder said that his company’s solution weighs only one-third of batteries for the same amount of energy. To compare to battery storage, one needs to compare both the storage and electrical conversion solution, so in this case, is the [weight of the storage cassette] + [weight of fuel cell making electricity] less than [weight of batteries yielding same KWh of electricity]? If they can make that work, they are on to something. I hope they are, but we really need to know the full picture.