Re: Solar-hydrogen home power system?

From: George William Herbert (gherbert_at_retro.com)
Date: 10/26/04 

Date: 26 Oct 2004 04:48:02 GMT

Don Lancaster <don@tinaja.com> wrote:
>George William Herbert wrote:
>> Don Lancaster <don@tinaja.com> wrote:
>> > [...]
>> >A common misconception.
>> >The latest of modern multicycle power plants with bottom cycling
>> >routinely approach 60 percent thermal efficiency.
>>
>> Still 10% lower than SFOC fuel cells.
>
>You are confusing the theoretical lab efficiency with the fully burdened
>amortization efficiency.
>
>The latter is NEGATIVE for SFOC fuel cells today.

And the fully burdened amortization efficiency of growing
plants, burying them under silt for tens of millions of
years of process time, and then having to dig them up is?
Do you have any concept of what a hundred and eighty
million years of internal rate of return does to your
amortization calculations? You're killing accountants
just posing the problem.

The interesting comparisons are what cycles can we do
when (a) the petroleum eventually runs out or
(b) we finally stop using (or at least, releasing)
fossil carbon fuels.

Your analysis is not more insightful. You are merely
using a different boundary condition, and cheating on
how you describe the problem to puff yourself up.

I am not rabidly enthusiastic about hydrogen vehicles
in any sense. My personal favorite renewable fuels
are either (methanol/ethanol) or thermally depolymerized
plant materials turned into diesel fuel. Those are a
lot easier to handle and probably cheaper cycles to set
up and use.

But unlike you, I have worked with hydrogen, and I have
paid enough attention to what it really can and can't do,
and I don't think you have any sort of vaguely useful
approach to criticizing it at all.

I frankly cannot respect anyone who spends their time
changing boundary conditions to make fraudulent debating
points and who is so afraid of liquid hydrogen and the
safety concerns of hydrogen fuels.

In the San Francisco / San Jose area (SF Bay Area) you see
just about as many tanker trucks full of LH2 (about ten
cubic meters per trailer) as you do propane out on the
freeways. Hydrogen is used in bulk in semiconductor
processing. I can't recall hearing of any accidents with
hydrogen tankers. Several propane tankers have blown up
for one reason or another in the last 20 years. Hell, we
had a gasoline tanker explode in one of the bores of the
Caldecott Tunnel a couple of decades ago, killing a couple
of dozen people if I recall right.

I know a bunch of fire personnel and hazmat team people.
None of them are more afraid of liquid hydrogen than
they are of gasoline or propane. None. They are frankly
more afraid of LOX, which also is transported in large
quantities. Or large quantities of fluorine compounds.

Spilling hydrogen causes a flammability hazard and
possibly a low energy fuel-air explosion. The low
density of LH liquid and low boiling temp makes it
boil off rapidly, and the gas dissipates rapidly
and effectively.

Spilling LOX causes an equal or worse flammability
hazard and can lead to substances as inert as asphalt
and rubber tires out and out detonating, not just
deflagrating. It boils much more slowly and the
vapors typically stay near the ground, in clouds
of high oxygen concentration that will burn organics
and vehicles and buildings to ash and rust in
short order if there's an ignition source nearby,
such as a vehicle motor running.

You need perspective. Spend time where LH2 is
handled routinely and actually get to know what
its risks and hazards are.

-george william herbert
gherbert@retro.com

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