Re: Congress Passes H-Prize

[email protected] wrote:
> 
> If I remember correctly the propaganda from many years ago, existing natural 
> gas pipes could be used for hydrogen, delivering similar energy at a similar 
> pressure with higher volumetric flow rate.

I'd be very cautious about actually attempting this.  Natural gas 
doesn't produce hydrogen embrittlement (or at least not in a big way) 
while hydrogen does -- in a BIG way.  The problem is that the hydrogen 
radical (an unbound single atom) is so small it can slither between the 
atoms of metals -- but not so small that doing so doesn't change the 
characteristics of the metal crystals ("grains") that largely determine 
the properties of the metal in bulk quantities.  Upshot is that metals 
(steels and aluminum alloys for certain, that I'm aware of) become 
brittle when exposed to hydrogen or some other materials that contain it 
in loosely bound form.  It's not a big problem with methane or coal gas, 
where the hydrogen has a nice, strong covalent bond -- but one of the 
reasons hydrogen gas is so flammable is that the bond between the two 
atoms is fairly weak; that lets the atoms split up and explore on their 
own, so to speak, which in turn renders the gas almost as invasive as 
helium (helium atoms are smaller than hydrogen radicals, but not a whole 
bunch smaller).

So, if you try to pump hydrogen through existing (steel) natural gas 
pipelines, you might run into huge problems with the pipeline, valving, 
infrastructure, etc., starting to literally crumble as the embrittlement 
proceeds to the point where a four foot diameter pipe will break from an 
impact comparable to a thrown rock -- releasing the gas with the widest 
known range of ignitable and explosive mixtures in air.

Further, attempting to use hydrogen as a replacement for natural gas in 
household applications has several other hazards -- first, the 
effectively invisible flame, second, the invasiveness of the gas, and 
third its extremely wide range of ignitable mixtures.  It's almost 
impossible to tell, by looking, if a hydrogen range burner is burning or 
not (possibly solvable by incorporating platinum etc. refractory wire 
that will glow in the flame -- platinum could also serve as a catalytic 
igniter, or as a resistance assisted igniter), but more importantly, the 
gas leaks through valves easily, collects at the ceiling, and forms an 
ignitable mixture in almost any proportion in air (something like 4% to 
94% hydrogen in air is ignitable, IIRC).  It has no odor (and adding 
odorants introduces many of the problems pumping hydrogen was intended 
to alleviate -- the mercaptans currently used with hydrocarbons would 
produce far more pollution than the hydrogen even in miniscule 
proportions), so leaks are hard to detect.

And if you ban hydrogen for household use (heating water and spaces, or 
cooking), then you obsoleted millions of home appliances when you switch 
natural gas pipes to hydrogen, even if you solve the problems with 
pumping hydrogen through steel pipes.

And in the end, hydrogen is an energy loss technology, just like ethanol 
(though with smaller losses, probably).  Electricity is used at point A 
to generate hydrogen, the hydrogen is shipped at some energy cost to 
point B, where it's burned (or, better, used in a fuel cell) to recover 
some portion of the energy used to generate it at point A.

Fuel cells and electric motors are pretty efficient (modern field coil 
motors routinely exceed 96% conversion, and I hear fuel cells are around 
90% these days if you have hydrogen to run them on).  Electrolysis 
isn't.  Reforming hydrocarbons uses energy, and the reformed hydrogen 
produces less than the original hydrocarbon would have (by at least the 
heat of combustion of the sequestered carbon) -- though it's possible 
the increased efficiency of fuel cells and electric motors vs. internal 
combustion or steam will offset this loss, and there's still the carbon 
cycle benefits to count in.

Bottom line, though, plain electricity is what we really need -- and a 
way to operate private vehicles on it without trying to store it 
chemically.  IOW, better batteries.

-- 
After you use everything you know and can find out to make what you're 
certain is the right decision, and it's too late to change things or 
back out -- you'll find out something that would have reversed the whole 
thing for you, if you'd only known in time.

Donald Qualls, aka The Silent Observer   http://silent1.home.netcom.com

Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.