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EV-based road transportation is not viable

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tom66:
Yes, I agree with nctnico.  Modern high pressure hydrogen systems are pretty safe.  The Mirai has a hydrogen leak detector and the most typical failure of a hydrogen tank would be a pinhole leak or a leaking valve, which would be readily detected by the sensor and alert occupants.  The bigger risks are filling stations which have to store hydrogen on site in compressed form, because it isn't usually produced on demand.  But even those are probably little more risk than propane tanks which are commonplace and the hazards are well understood - just position them well away from anything that could easily hit them and open sources of ignition.

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.

tggzzz:

--- Quote from: nctnico on February 20, 2023, 10:28:59 pm ---
--- Quote from: tggzzz on February 20, 2023, 05:15:19 pm ---
--- Quote from: tom66 on February 20, 2023, 04:56:22 pm ---Also I would have thought if hydrogen did have an application then train power would be a pretty good one - size of batteries vs a large hydrogen tank in place of diesel engine - but tank then needs to be sufficient to run for at least a significant part of the journey if the assumption is refilling hydrogen at a train station is not safe enough or too inconvenient.  (Diesel trains aren't refuelled at stations, either.)

--- End quote ---

Liquid hydrogen being transported on trains through towns?

--- End quote ---
Again: hydrogen isn't transported in liquid form. Only in gas form under high pressure. But it is not unsafer compared to any other fuel as it will also require oxygen to burn.

--- End quote ---

In terms of burning, yes. But there is also substantial energy stored when it is compressed, and if the container is punctured or a pipe severed, the pressure will make the gas escape in a jet. That might have different consequences to a puddle of diesel.

If you have solid references to what happens, I'm interested.


--- Quote ---I see people mentioning the Hindenburg: if you read a bit more about that accident you'll learn that the outer hull was made from extremely flammable material. Like a piece of cloth drenched in gasoline. It is not the hydrogen that caught fire, but the outer hull.

--- End quote ---

Indeed, but in such cases the perception of danger is important. Greenpeace knows that all too well :(

Recently conspiracy theorists and propagandists have learned how to use social media to spread their messages, often attached to "don't trust the experts, they are lying to you" statements. That complicates discussions, as evidenced by recent events in the UK and US.


--- Quote ---There is so much nitwitting going around. Last week I watched a documentary about Chernobyl. One of the interesting conclusions was that the huge increase of life threatening cancers (as predicted by Greenpeace et al) didn't happen.

--- End quote ---

Greenpeace has always been a bunch of twits that are prepared to use disreputable "explanations" and means to further their goals. Others are more reputable.

As to the number of cancers, I wouldn't trust any official figures from Russia or Belarus.

Covid has vividly shown how difficult it is to give accurate statistics for cause of death; the only statistic that is reliable is "excess mortality". Given that outside Belarus/Russia the radiation was much lower, it is to be expected that deaths "due to Chernobyl" can't be distinguished from other deaths. Hells teeth, there are some houses in towns near me where the radon causes as many lung cancers as smoking 20 fags/day! And then there's all the radiation emitted by coal burning power stations!

Certainly Chernobyl did cause noticable increases in radiation. It was only in the past few years that sheep in North Wales have been allowed back into the food chain. The radiation in Lapland was also of concern; I don't know what precautions were taken w.r.t. reindeer. In the aftermath of Chernobyl I remember once seeing a TV programme that showed a map of the radiation levels in the UK, and noting how the fallout from Chernobyl had made a beeline to Sellafield!

tggzzz:

--- Quote from: tom66 on February 20, 2023, 10:44:25 pm ---Yes, I agree with nctnico.  Modern high pressure hydrogen systems are pretty safe.  The Mirai has a hydrogen leak detector and the most typical failure of a hydrogen tank would be a pinhole leak or a leaking valve, which would be readily detected by the sensor and alert occupants.  The bigger risks are filling stations which have to store hydrogen on site in compressed form, because it isn't usually produced on demand.  But even those are probably little more risk than propane tanks which are commonplace and the hazards are well understood - just position them well away from anything that could easily hit them and open sources of ignition.

--- End quote ---

Er, no. Let's avoid using adjectives and look at the numbers...

Hydrogen is stored at 700bar/70MPa https://www.thechemicalengineer.com/features/hydrogen-in-vehicular-transport/
LPG release valves are at 25bar https://www.elgas.com.au/blog/1969-how-much-pressure-is-in-lpg-propane-cylinders-in-what-state/

700:25 is a good example of why "numbers not adjectives" is a good motto.


--- Quote ---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.

tautech:

--- 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.

PlainName:

--- Quote ---One of the interesting conclusions was that the huge increase of life threatening cancers (as predicted by Greenpeace et al) didn't happen.
--- End quote ---

Perhaps because everyone got evacuated?

I recall a documentary some time ago that postulated that some level of radiation was better than no, or low, level since it triggers the body's repair mechanism.

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