General > General Technical Chat
EV-based road transportation is not viable
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tautech:

--- Quote from: Miyuki on February 21, 2023, 09:57:07 am ---
--- Quote from: tautech on February 21, 2023, 01:32:53 am ---
--- Quote from: tggzzz on February 21, 2023, 12:00:49 am ---
--- Quote from: tautech on February 20, 2023, 11:31:35 pm ---
--- Quote from: tggzzz on February 20, 2023, 11:16:36 pm ---
--- Quote from: tom66 on February 20, 2023, 10:44:25 pm ---For a train, the biggest risk is a derailment. You could probably reduce the risk of a hazardous hydrogen leak by placing the tank towards the rear of the vehicle.

--- End quote ---

Or being rear-ended, or rear-ending.

--- End quote ---
The same concerns have been aired for decades about CNG powered vehicles.
History has shown us it's no more unsafe than liquid fueled vehicles.

--- End quote ---

Hydrogen 700 bar. LPG 25 bar. That's a significant difference.

--- End quote ---
CNG is NOT LPG !
https://www.diffen.com/difference/CNG_vs_LPG

~200 bar (~3000 PSI) is CNG tank pressure for automotive use.
It's primary disadvantage was low BTU in an ICE which translates to limited range.
LPG is better in many respects in an ICE.

Still, we had CNG and LPG powered cars in NZ for decades after the 70's oil shock.

--- End quote ---
And modern CNG systems going to rise that pressure even further, with new vessels rated up to 450 bar

--- End quote ---
Thanks, that's interesting as it will rekindle CNG in ICE in some parts where they have plenty of it.
tggzzz:

--- Quote from: tautech on February 21, 2023, 01:32:53 am ---
--- Quote from: tggzzz on February 21, 2023, 12:00:49 am ---
--- Quote from: tautech on February 20, 2023, 11:31:35 pm ---
--- Quote from: tggzzz on February 20, 2023, 11:16:36 pm ---
--- Quote from: tom66 on February 20, 2023, 10:44:25 pm ---For a train, the biggest risk is a derailment. You could probably reduce the risk of a hazardous hydrogen leak by placing the tank towards the rear of the vehicle.

--- End quote ---

Or being rear-ended, or rear-ending.

--- End quote ---
The same concerns have been aired for decades about CNG powered vehicles.
History has shown us it's no more unsafe than liquid fueled vehicles.

--- End quote ---

Hydrogen 700 bar. LPG 25 bar. That's a significant difference.

--- End quote ---
CNG is NOT LPG !
https://www.diffen.com/difference/CNG_vs_LPG

~200 bar (~3000 PSI) is CNG tank pressure for automotive use.
It's primary disadvantage was low BTU in an ICE which translates to limited range.
LPG is better in many respects in an ICE.

Still, we had CNG and LPG powered cars in NZ for decades after the 70's oil shock.

--- End quote ---

I wasn't aware of that; thanks.

It seems there are some CNG filling stations in the UK.
If my count is right there are 29 of them, and 13 are open to the public.
https://www.glpautogas.info/en/cng-stations-united-kingdom.html

LPG is far more widely available, and based on limited old experience, relevant to cars. (In the 80s I saw a car transition between LPG and petrol while moving).

Hence, in the UK at least, there is plenty of CNG in the ground but CNG in vehicles is a rarity for reasons I don't know (but can guess).  I would hesitate to draw general conclusions about its characteristics if widely employed.
tggzzz:

--- Quote from: Ice-Tea on February 21, 2023, 09:52:28 am ---Flamability range:



Activation energy:



--- End quote ---

Useful comparisons. Thanks.
nctnico:

--- Quote from: tggzzz on February 21, 2023, 11:20:30 am ---
--- Quote from: Ice-Tea on February 21, 2023, 09:52:28 am ---Flamability range:


Activation energy:


--- End quote ---

Useful comparisons. Thanks.

--- End quote ---
It is not at all. Just more fear mongering. Hydrogen is very light so it will move up quickly (out of the building) where gasoline, natural gas and LPG vapours will sink forming a blanket. So the chance you'll actually get an explosion or fire from hydrogen is far lower. Putting things further into perspective: you'll need a fairly small space to achieve a flammable hydrogen mixture. With 5kg (typical for a hydrogen car) of hydrogen you'll need less than 6 parking spaces worth of air volume. All in all a hydrogen leak from a car is far less of a problem compared to a car leaking CNG, LPG or gasoline.
tggzzz:

--- Quote from: nctnico on February 21, 2023, 12:19:23 pm ---
--- Quote from: tggzzz on February 21, 2023, 11:20:30 am ---
--- Quote from: Ice-Tea on February 21, 2023, 09:52:28 am ---Flamability range:


Activation energy:


--- End quote ---

Useful comparisons. Thanks.

--- End quote ---
It is not at all. Just more fear mongering. Hydrogen is very light so it will move up quickly (out of the building) where gasoline, natural gas and LPG vapours will sink forming a blanket. So the chance you'll actually get an explosion or fire from hydrogen is far lower. Putting things further into perspective: you'll need a fairly small space to achieve a flammable hydrogen mixture. With 5kg (typical for a hydrogen car) of hydrogen you'll need less than 6 parking spaces worth of air volume. All in all a hydrogen leak from a car is far less of a problem compared to a car leaking CNG, LPG or gasoline.

--- End quote ---

Nobody claimed it is the whole story.
Nobody claimed it is the only story.

Nonetheless, it is a useful quantitative starting point for stories.
And a better starting point than adjectives.
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