I looked at an article by DOE
http://www.hydrogen.energy.gov/permitting/pdfs/45408.pdf
and they concur with you about burning vertically, there are other
factors to consider.
- is flammable in a much wider range of air mixture
- flame spreads 10x faster
- unburned gas diffuses 4-6x
These factors would dramatically increase the danger in enclosed spaces
such as garages and tunnels and inside a vehicle. Unlike a propane
torch, where the gas coming out the nozzle is in high concentration and
won't ignite, hydrogen will - easily. In an enclosed space, a leak of
gas can spread very quickly and find an ignition source quicker.
Because the flame spreads fast and the diffusion would provide plenty of
O2, the burning would be almost instantaneous, creating an explosion
beyond imagination.
Also, the flame is invisible so, if there's a burning leak, it's very
hard to detect.
Peri
------ Original Message ------
From: "Ben Goren via EV" <ev@lists.evdl.org>
To: "Russ Sciville" <rustyb...@yahoo.co.uk>; "Electric Vehicle
Discussion List" <ev@lists.evdl.org>
Sent: 24-Apr-15 8:16:25 AM
Subject: Re: [EVDL] Toyota FCV runs on Musk's bull$$it
On Apr 24, 2015, at 6:03 AM, Russ Sciville via EV <ev@lists.evdl.org>
wrote:
Who would wish to drive around with a hydrogen tank in the back
pressurised to 10,000 psi?
There's lots of insanity associated with FCVs, but fuel safety isn't
part of it. Hydrogen is much safer than gasoline in that regards. Not
that gasoline is especially safe, of course, but it's a well-accepted
and well-managed risk, and hydrogen is a lesser risk than that.
Gasoline vapors are heavier than air and tend to pool. Liquid gasoline
wicks very easily into fabric. Gasoline fires stay close to the ground
and in your clothes.
Hydrogen is the most buoyant gas there is. An hydrogen leak is going
straight up and isn't going to collect anywhere in enough volume to
sustain combustion. If you started an hydrogen fire, the flames are
going to shoot right up rather than spread laterally. And, unlike
gasoline fires which are excellent at sustaining themselves, the
slightest interruption of an hydrogen flame is going to extinguish it.
Indeed, even creating a sustaining flame in the first place is going to
be a bit of a challenge -- think of how careful you have to be to light
a propane torch; hydrogen will be even more challenging.
Pressurized tanks can be scary, yes, but, in practice, it takes either
malicious intent or something spectacularly catastrophic to set off one
built to automotive specs.
Where hydrogen falls flat is first in terms of pollution. Hydrogen is
commercially sourced from mined hydrocarbons and thus is as much of a
CO2 pollutant as the coal, oil, or gas it's produced from. Because it's
the lightest and most highly possibly refined form of those
hydrocarbons, it next loses out on efficiency (for the same reason
gasoline loses to diesel) -- especially compared with electric
vehicles. It loses out in a really big way in terms of the distribution
network which doesn't exist for hydrogen but does for everything else
-- and which would be much more challenging and expensive and less
efficient to build than anything else we've already built. And it loses
out to gasoline and diesel in terms of practicality because...well,
while hydrogen has far and away the greatest energy density per unit of
_mass,_ it's also got the _least_ energy density per unit of _volume._
A fifteen gallon tank of hydrogen gas, under any form of compression
you'd want to be anywhere n
ear, contains _far_ fewer hydrogen atoms than a fifteen gallon tank of
gasoline.
Hydrogen is a great fuel...for rocket ships in space. Here on Earth?
Forget it.
Cheers,
b&
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