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255Wh/kg? That’s not true. About 300Wh/kg has been available for over a decade. The next Gen lithium metal anode and lithium sulfur batteries can do 400-500Wh/k

255Wh/kg? That’s not true. About 300Wh/kg has been available for over a decade. The next Gen lithium metal anode and lithium sulfur batteries can do 400-500Wh/kg, up to 650Wh/kg in the lab.

walrus01 4y ago
I'm referring to li ion cylindrical cells in the 18650, 20700 and 21700 formats which are commercially available right now. Which I can buy online in 5 minutes with my visa card from a battery wholesaler. If you can find me the pdf datasheet for one that's above that I'd love to see it! And even better a vendor link. Note I am also referring to something like the actual usable watt hours from a battery before you discharge it below "permanently damaged" state, in the range starting from 100% SOC standard full voltage and manufacturer's do-not-exceed floor voltage. Such as on the NCR18650GA. I don't doubt there are specialty rare "ask us for a price" low volume 300Wh/kg in circulation if you have the right contacts.
- Robotbeat 4y ago
  Okay, but you can’t get a non-science-kit fuel cell of decent size online in 5 minutes with my visa card from a battery wholesaler. You need the right contacts.
  - allisdust 4y ago
    We can: https://www.fuelcellstore.com/ https://www.fuelcellstore.com/ Their max fuel cell stack goes up to 6kw so its no longer in hobby territory.
    - Robotbeat 4y ago
      Thanks! Still pretty expensive and heavy for just a 6kW fuel cell stack alone! $27,000 is the base MSRP for a Chevy Bolt, before incentives.
henearkr 4y ago
So we're down to only a 50% energy density compared to a fuel cell. But the fuel cell uses hydrogen, which leaks inevitably (it slowly diffuses through all materials), and is an extremely potent greenhouse effect gas.
- ema 4y ago
  How long does it take for hydrogen floating in the atmosphere to react with the oxygen?
  - henearkr 4y ago
    Your question would make sense only if it was a direct greenhouse effect gas, but H2 effect is indirect (but still huge), precisely in the way it disappears by combining with other molecules. The greenhouse effect of H2 is by reacting with the HO naturally present in the atmosphere (giving water vapour: 2 HO + H2 -> 2 H2O), thus reducing the concentration of HO, and thus modifiying the dynamics of atmospheric methane and ozone. From my understanding, in the atmosphere, HO has an important role in the decay of CH4. http://agage.mit.edu/publications/global-environmental-impacts-hydrogen-economy http://agage.mit.edu/publications/global-environmental-impac...
- semi-extrinsic 4y ago
  No, that is factually incorrect, hydrogen is not an "extremely potent" greenhouse gas in this context. Hydrogen has a GWP of 11, meaning it is 11 times worse than emitting CO2. Methane, for example, has a GWP of 34, which is starting to get kind of bad, but "extremely potent" is something like SF6 wich has a GWP of 22800. Furthermore, GWP is calculated on a mass basis, which skews things a lot for a light molecule like hydrogen. I'm kind of astonished at the fear mongering on this issue, because it means people cannot be arsed to spend 20 minutes on Google with a calculator to check the numbers before they spread something as a truth. Let's do the actual math. If you look at a Toyota Mirai, it needs 5 kg of hydrogen to get a 300 mile range. A comparable diesel car needs 28 kg diesel to get that range, and will emit 88 kg of CO2 when that diesel is burned (the O's in CO2 comes from the air). Even if the hydrogen car had an absurdly high leakage rate of 50% during that trip and the period it stood still before next trip, it would still emit only the equivalent of 27.5 kg of CO2. So at insanely high leakage rate, diesel is still 3x worse than hydrogen. If we are realistic about leakage rate, published numbers from actual measurements with the Toyota Mirai placed in a sealed container gives us 2 mL/min at 1 bar, so the time to leak the entire contents of the tank is more than 3000 days. So let's say this is a hobby vehicle (like a small aircraft) seeing infrequent use, you consume two tanks of hydrogen per month. That puts your leakage rate at 0.5%, giving an emissions equivalent of 0.56 kg CO2, while the diesel (avgas) powered equivalent would emit 166 kg CO2 - 300x worse. Note that this is all based on technology that is already here - you can go buy it today - not some hypothetical developments.

255Wh/kg? That’s not true. About 300Wh/kg has been available for over a decade. The next Gen lithium metal anode and lithium sulfur batteries can do 400-500Wh/kg, up to 650Wh/kg in the lab.

walrus01 4y ago

I'm referring to li ion cylindrical cells in the 18650, 20700 and 21700 formats which are commercially available right now. Which I can buy online in 5 minutes with my visa card from a battery wholesaler. If you can find me the pdf datasheet for one that's above that I'd love to see it! And even better a vendor link. Note I am also referring to something like the actual usable watt hours from a battery before you discharge it below "permanently damaged" state, in the range starting from 100% SOC standard full voltage and manufacturer's do-not-exceed floor voltage. Such as on the NCR18650GA. I don't doubt there are specialty rare "ask us for a price" low volume 300Wh/kg in circulation if you have the right contacts.

Robotbeat 4y ago
Okay, but you can’t get a non-science-kit fuel cell of decent size online in 5 minutes with my visa card from a battery wholesaler. You need the right contacts.
- allisdust 4y ago
  We can: https://www.fuelcellstore.com/ https://www.fuelcellstore.com/ Their max fuel cell stack goes up to 6kw so its no longer in hobby territory.
  - Robotbeat 4y ago
    Thanks! Still pretty expensive and heavy for just a 6kW fuel cell stack alone! $27,000 is the base MSRP for a Chevy Bolt, before incentives.

henearkr 4y ago

So we're down to only a 50% energy density compared to a fuel cell. But the fuel cell uses hydrogen, which leaks inevitably (it slowly diffuses through all materials), and is an extremely potent greenhouse effect gas.

ema 4y ago
How long does it take for hydrogen floating in the atmosphere to react with the oxygen?
- henearkr 4y ago
  Your question would make sense only if it was a direct greenhouse effect gas, but H2 effect is indirect (but still huge), precisely in the way it disappears by combining with other molecules. The greenhouse effect of H2 is by reacting with the HO naturally present in the atmosphere (giving water vapour: 2 HO + H2 -> 2 H2O), thus reducing the concentration of HO, and thus modifiying the dynamics of atmospheric methane and ozone. From my understanding, in the atmosphere, HO has an important role in the decay of CH4. http://agage.mit.edu/publications/global-environmental-impacts-hydrogen-economy http://agage.mit.edu/publications/global-environmental-impac...
semi-extrinsic 4y ago
No, that is factually incorrect, hydrogen is not an "extremely potent" greenhouse gas in this context. Hydrogen has a GWP of 11, meaning it is 11 times worse than emitting CO2. Methane, for example, has a GWP of 34, which is starting to get kind of bad, but "extremely potent" is something like SF6 wich has a GWP of 22800. Furthermore, GWP is calculated on a mass basis, which skews things a lot for a light molecule like hydrogen. I'm kind of astonished at the fear mongering on this issue, because it means people cannot be arsed to spend 20 minutes on Google with a calculator to check the numbers before they spread something as a truth. Let's do the actual math. If you look at a Toyota Mirai, it needs 5 kg of hydrogen to get a 300 mile range. A comparable diesel car needs 28 kg diesel to get that range, and will emit 88 kg of CO2 when that diesel is burned (the O's in CO2 comes from the air). Even if the hydrogen car had an absurdly high leakage rate of 50% during that trip and the period it stood still before next trip, it would still emit only the equivalent of 27.5 kg of CO2. So at insanely high leakage rate, diesel is still 3x worse than hydrogen. If we are realistic about leakage rate, published numbers from actual measurements with the Toyota Mirai placed in a sealed container gives us 2 mL/min at 1 bar, so the time to leak the entire contents of the tank is more than 3000 days. So let's say this is a hobby vehicle (like a small aircraft) seeing infrequent use, you consume two tanks of hydrogen per month. That puts your leakage rate at 0.5%, giving an emissions equivalent of 0.56 kg CO2, while the diesel (avgas) powered equivalent would emit 166 kg CO2 - 300x worse. Note that this is all based on technology that is already here - you can go buy it today - not some hypothetical developments.