The question seems to be aimed at fuel cell technology.

> Hydrogen is not a source of energy -- it's a storage medium.

That's an appropriate response, but you don't go from there
to the hows and whys of fuel cells as energy transducers to
assist Drtrider34 with the professor's questions. Some pointer
to the issues of platinum vs nickel electrodes might have been
helpful, like a nickel-catalyzed cell has to be run hotter.

> SOLAR
> "Several studies indicate that to enjoy a relatively high
> standard of living, our optimum human population should be
> 200 million or less (Pimentel et al., 1994a)."
> http://www.envirolink.org/orgs/gaia-pc/Pimentel2.html

This one is the crux. The population studies you cite aren't primarily aimed at the solar energy issue, and their treatment
of solar considerations is quite inadequate.

> With 100 million being "ideal": http://dieoff.org/page136.htm

All the citations of this study are more than 10 years old.

> At that point, America's economic machine
> is "out of gas" -- permanently.
>

> The positive feedbacks of oil depletion are going to provide a
> lot of unpleasant surprises in the next couple of decades.
>
> Jay

You present an exhaustive survey of the main energy sources
available, with a well reasoned pessimism regarding fossil fuels,
currently the main energy source, and wind up with a bleak
overview of the energy future overall. Yet I want to call your
attention to some aspects which could turn out more promising,
if the cards fall right.

It's true there are too many people, and that's not getting any
better. What can't be cured, must be endured. That doesn't have
to mean that we must have a catastrophic population crash in the
near future. Our job in technology is to prevent that if we can.
the problem is a tough one. A factor you failed to discuss makes
it even tougher. There is too much oxidized carbon in the air,
largely because we burn too much carbon-containing fuel. That
is making the planet hotter, with unpredictable results which
likely include catastrophes, on the same time scale as exhaustion
of fossil fuels.

Thus this newsgroup. So many of our technologies rely on fuel use,
the answer to carbon-free fuel is hydrogen. Hydrogen produces no pollutants when burned in air, and specifically no oxides of carbon.
it has drawbacks we will have to work around, like its bulk. We can
live with that. What we cannot do is continue to put excess carbon
species into the atmosphere. That option is rapidly closing off,
and none too soon. Both poles are melting now. The general problem
with heating is that thermal effects tend to have positive feedback
mechanisms: when you cross a temperature threshold for some phenomonon, that phenomonon is very likely to be exothermic, or
heat-producing in its own right. You can't put the genie back in the
bottle. Thermodynamic irreversibility is not something I like to
hear about when it's being applied to where I live. Let's not delve
into this too deeply, but it's scary. Economics can go hang. We must
quit putting carbon in the air as soon as possible, if we have to
hang the economists to do it.

What I wanted to talk about was solar energy. As you said, hydrogen
is not an energy source. Solar energy is, and it has been
systematically underestimated. Should every south-facing roof in the
US be covered with photovoltaic cells at 5% efficiency, that would provide all needed energy. Every power plant and every petroleum
refinery could be scrapped, every coal mine and every nuclear reactor
shut down. The energy problem is not intractable for any technical
reason. The intractability lay with those economists, whom we left
swinging on ropes in the preceding paragraph.

No one proposes to cover the southern half of every roof with solar
cells. The reason is their lousy efficiency figures. To convert
sunlight to electricity, the most efficient way is to use tracking
concentrating reflectors, make steam and put the steam through
turbines, and use the turbines to drive generators. The efficiency
is five to ten times as good, but you can't put it on rooftops.
A tradeoff is that a tracking concentrator is a moving part, so
it requires maintenance. Boilers, turbines and generators do too.
yet it is quite possible to derive all needed energy from solar
energy in various forms, without dedicating prime land to the purpose. Orbital energy proposals require land only for power
downlinks, while floating energy farms use no land area. There
is no technical reason why all energy needs cannot be supplied
by the Sun. All that is lacking is the resolution to take this
course.

Hydrogen fuel may be provided by direct electrolysis of water,
but a more direct method is photo electric conversion using
semiconductor junctions submerged in water illuminated by the
sun. This gives an efficiency advantage, and efficiency is the
bottom line in energy production. Solar hydrogen production
needs to be put on line soon. The pricing advantage currently
attributed to thermal reforming of natural gas is an artifact
of the fossil fuel based economy, and will disappear when it
becomes necessary to stop the release of the byproduct carbon
gas. Like I said, that can stop any time we get around to it.

So it is inevitable that the future economy will be based on
solar energy and hydrogen fuel. That is a mathematical certainty,
for if it does not happen we will die. Even economists will
eventually pay attention to that ultimate logic.

Respectfully,
Johnny Thunderbird
heavyLight Books http://www.oocities.org/~jthunderbird
Re: Hydrogen is Not a Source of Energy - It's a Storage Medium sci.energy.hydrogen 980531