Re: H2

[Richard Tarara <rbtarara@SPRYNET.COM>]

Energy payback for current and proposed system seem to be on the order of
1-4 years.

http://www.azom.com/details.asp?ArticleID=1119

The advantage of using solar to produce H2 would be that you eliminate the
problem that solar is not 'energy on demand'.  The same goes for using wind
power.  Setting up large solar and wind farms to produce hydrogen which
would be piped (at great infra-structure expense--estimates of $5 trillion
from one of my class projects) either to fuel suppliers for transportation
or as a substitute for natural gas in all its uses.
In fact, using H2 to power electrical generation in urban areas might make
sense.

I would see the only advantage to using nuclear as the ability to locate
plants far from population centers.  On the other hand, the high-density
energy output of nuclear plants makes them perfect FOR population centers.
What would make more sense to me is to use off-hours production of nuke
plants to produce hydrogen (since nuke plants usually run near capacity
24-7).

The big problem with all of this is the overall efficiency of the process
of collecting energy by solar, wind, nuclear, etc.  then converting to
hydrogen then shipping the hydrogen and then reconverting the H2 to energy.
The overall cycle efficiency then requires considerably more primary
capacity.  This is where it starts to hit the fan!  Design a system for a
future population of say 500 million people at say 75% of today's energy
usage (reduction due to consumption efficiency and conservation) but
eliminate the use of oil and natural gas (throw in coal if you want to make
it really difficult) and do the numbers.  You need literally tens of
millions of 1 megawatt wind generators and tens of thousands of miles of
solar collection (compare to the area of _all_ paved roads).    Throwing
nuclear into the mix still would require maybe 1000 large plants.
Replacing the 90% of current energy use that is from fossil fuels in an
enormously complex and EXPENSIVE proposition.

Rick

see http://www.saintmarys.edu/~rtarara/ENERGY_PROJECT/ENERGY2100.htm

for more student generated projections.

****************************
Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu

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> [Original Message]
> From: Frohne, Vickie <VFrohne@BEN.EDU>

> Turns out that solar power isn't the cure-all and end-all of long-term
> energy shortages because the energy density, availability duty cycle, and
> collection efficiencies are all low. Furthermore, it's not clear to me
that
> the energy required to manufacture a photovoltaic cell, from raw materials
> to finished product, would be recovered over its operation lifetime. Does
> anyone have any data or insights on this?  IMHO, using sunlight to make H2
> will be a commercial success only if photovoltaics are not involved, and
> when, not if, the energy shortage becomes acute enough to drive the price
> way up.