Re: Congress Passes H-Prize

[email protected] wrote:

> Dear Donald,
> 
> Thanks for the tutorial.  You would have thought the people proposing a 
> "hydrogen economy" would have thought of some of these things...

Based on my (admittedly limited) reading of recent history, humans don't 
have a good record on this.  I'm sure there are engineers involved in 
making hydrogen work who have -- but the people who paint the rosy 
pictures they use to try to sell hydrogen to investors and consumers, if 
they know about problems like these at all, will try to sweep them under 
the rug.

> If I wanted a hydrogen flame to be visible, I'd use a gaseous additive.  
> Maybe 1% methane would do the trick?

Uncertain, but I'm doubtful it would be visible enough.  It's 
incandescent carbon in the flame that makes a flame bright.  Ethanol has 
a much higher carbon content than hydrogen plus 1% methane, and still 
has a flame that's quite hard to see (especially in sunlight).  Even 
pure methane (essentially, natural gas is pure methane plus some methyl 
mercaptan to make it smell) makes a flame that's faint enough to be hard 
to see in strong light, if it's well mixed with air, though it's visible 
enough indoors.  I'd expect, though, that you'd need 10% or more of 
methane to make a flame visible enough for safety, which is more than 
enough carbon to cause trouble with fuel cells -- at which point, why 
bother reforming the gas, when you can just pump the natural gas, cheaper?

> The amount of stinker chemicals needed to make the H2 noticeable would be 
> down in the parts per million, and need not be environmentally deleterious.

Commercially sold propane has, IIRC, around 100 ppm of butyl mercaptan 
added, which makes it adequately stinky -- that's about .01%.  Perhaps 
it wouldn't be a big deal environmentally (it's certainly no problem in 
natural gas and propane/butane products as commonly sold and used), but 
I don't think the mercaptan component would go at all well in a fuel cell.

> Embrittlement is certainly a problem. 

Yep, that's the big one.  If a crude oil pipeline cracks and leaks, you 
have a mess.  If a natural gas pipeline cracks and leaks, you have a 
major problem (just happened a few days ago, Nigeria, IIRC, killed 
several hundred people).  A hydrogen pipeline will be at least as bad as 
natural gas, and much more likely to break in the first place.

And all to pump gas that could be pumped more efficiently before 
reforming.  Please note: at the same temperature and pressure, there's 
twice as much hydrogen in a given volume of methane as in the same 
volume of hydrogen (this ratio is even more so for liquid hydrocarbons 
of any molecular weight).  Even if you NEED hydrogen as the end product, 
it's more efficient, as well as safer, to pipe the natural gas and 
reform at the point of consumption -- assuming you're reforming natural 
gas to get the hydrogen.  If you're using electricity to break down 
water, it's more efficient to transmit the energy as electricity and do 
the electrolysis at the "last mile".

Which is to say, our existing infrastructure is better for a hydrogen 
economy than an upgrade or replacement to handle hydrogen the way we now 
handle natural gas.

-- 
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.