On Fri, 08 Jun 2007 06:13:22 -0700, John Smith I
wrote:

Roger (K8RI) wrote:

...
I doubt any one is arguing that Hydrogen is generated, the problem is
it is a very inefficient process both from how much hydrogen is
generated compared to how much RF it takes to generate that Hydrogen.
...

The most efficient solar cells are about 20% efficient, efficiency is in
the eye of the beholder. With an, almost, never ending supply of
sunlight--they suddenly begin to make sense ... a two fold increase in
efficiency would change everything, yet still be only 40% efficient.

The replacement of batteries with storage tanks is an economic advantage
of hydrogen over electric ... and an IMPORTANT one, well, until better
and more efficient batteries come along.

...
... Using microwaves they come off mixed
which is not a good thing. Looks spectacular but not very useful.

They come off in exactly the necessary ratio to burn at 100% efficiency.

Unfortunately they are mixed in that ratio and there is no safe way to
store much comprised of that ratio. They need to be separated to be
stored safely. Hydrogen can be stored in a metal sponge (Metal
Hydride) which is quite efficient. Expensive, but efficient.

Now, a way make lemonade from that "lemon" is only necessary ...

...
Trucking H2 is expensive and piping it much of any distance as a
liquid is out of the question.

Yeah, I'd pipe it as a gas ... allowing its' own pressure to "pump" it.

The problem with piping it as a gas is transferring sufficient volume
and then it'd have to be liquefied at the receiving end. Another
problem is keeping it liquid. You really can't carry a lot as a gas
under pressure and it takes a lot to develop much energy/power as the
stuff is so low in BTU content.


Taken out of context it is true that a Hydrogen spill dissipates much
more quickly that a gasoline spill, BUT while it is dissipating it is
far more explosive. OTOH a given volume of H2 has far less energy/BTU
than gas. Put in perspetive both dynamite and TNT also have less
energy per unit volume than does gas. The problem is the speed of the
combustion front. In the end it's not quite true that a liquid H2
spill is safer than a gas spill.

Depending on the speed of release/"moment of ignition", the bulk of the
hydrogen burn/explosion is going to be well above your head ... hydrogen

I've been around a couple of H2/air explosions. H2 by itself does rise
rapidly, but it is so active physically it mixes with the air and the
rise is not nearly as fast although it does dissipate relatively
quick. OTOH you have to get rid of almost all of it before it is no
longer dangerous from an explosive point. The lower explosive limit
(LEL) is only 4% while the Upper Explosive Limit (UEL) is 96% meaning
if it's present it's probably within the explosive range.

Another problem with H2 is it doesn't take much flow to create a
substantial electrostatic charge resulting in a spark and ignition. In
both cases I'm familiar that was the cause of the explosion. In the
one case a worker was standing within a couple of feet of the large
container which was at low pressure. Just a couple inches of water
pressure above atmosphere. He was looking at it when it blew. You
could see the imprint of his goggles and shape of his face in the
Aluminum. He did survive, but it was a couple of days before he could
hear again. Pretty amazing as it basically blew him through the
equivalent of a wall. In the other case it blew a worker through the
"blow out panels" in a wall plus about 30 to 50 feet. He was back to
work the next day.

In both cases there was enough air movement that the bulk of the force
was within a few feet of the floor.

snip