Debate Summary - SPS vs. Wind/Solar/Hydrogen

Arthur-

Thanks for the numbers!

I'll admit to handwaving on the costs of a complete hydrogen based
system for home use; I'm assuming costs will drop greatly in the next
decade or so if the technology is mass adopted and new R&D breakthroughs
come into production (like carbon nanotubes for hydrogen storage). I'm
kind of also expecting whatever becomes popular for hydrogen powered
cars like the "HyperCar":
http://www.rmi.org/sitepages/pid446.php
will be adapted for home use. One of the reasons I'm holding out on a
new car is I'm kind of hoping for one of those upcoming hybrids that can
also be used as a backup generator for a house (our car mostly sits
unused as we work from home mainly) once they get the bugs out. The
convergence of automotive and household technology is quite fascinating.

For your cost estimates projected forward ten or twenty years (the SPS
timescale), the real issue then is how fast are these costs going to
come down? No one knows for sure obviously -- there are just hints of
breakthroughs in various technologies using better materials science for
PV and fuel cells / nanoturbines and hydrogen storage (such as the
STMicroelectronics, announcement, which may yet turn out to be hype).
http://www.cnn.com/2003/TECH/biztech/10/02/solar.cells.reut/
"Thursday, October 2, 2003 ... A major European chip maker said this
week it had discovered new ways to produce solar cells which will
generate electricity twenty times cheaper than today's solar panels."

I think in the end it comes down to in part a question of will
incremental R&D on these issues over the next twenty years result in
better earthly solutions or better SPS solutions. Also, in making
projections, it is always a question of whether the growth is linear or
exponential.
http://www.kurzweilai.net/articles/art0134.html
In PV, I suspect the cost reductions will be exponential,
same as with computer technology. But, it is just a gut feeling there.
Certainly though process R&D is more likely to happen on Earth, and
those sorts of process innovations may not be directly applicable to use
in space given a simpler industrial infrastrucuture likely available in
using lunar or asteroidal ore, so PV cells may be cheaper and more
efficicient than what could readily be manufactured in space.

By the way, I think gas turbine costs burning Hydrogen may be much lower
than that fuel cells -- but may have higher operational costs for
maintenance and lower efficiency? I thought gas turbines were more
around $350/kW capital cost for larger installations.

For home use, cost might of course be higher for hydrogen storage and
electricity production.

For hydrogen storage one might look at this as a starter example:
http://www.hydrogenappliances.com/hydrogengeneration.html
who quote a 250 gallon Hydrogen generation and storage unit at $5495.95.

How much energy does that amount of Hydrogen store?

Some figures for a calculation:
http://evworld.com/databases/storybuilder.cfm?storyid=502&subcookie=1
"Typically, a match has about one Btu, whereas a gallon of gasoline has
about 115,000 Btus. A gallon of liquid hydrogen has 30,000 Btus, which
explains why a liquid hydrogen tank is about 4 times larger by volume
than a gasoline tank. It is also worth noting that a kilowatt hour of
electricity has 3,412 Btus."

http://mb-soft.com/public2/hydrogen.html
"Hydrogen does have some more significant drawbacks. One of the most
difficult to deal with is that it is such a light gas! A pound of
Hydrogen contains around 61,000 Btus of latent energy in it, which seems
like a lot! For comparison, a pound of regular gasoline only contains
around 20,500 Btus in it! Sounds good! However, a pound of Hydrogen is
HUGE! At standard atmospheric pressure and temperature, it takes up
around 190 cubic feet of space. In contrast, that pound of gasoline only
takes up about 1/50 of a cubic foot. We can say this same thing in terms
of "gallons". A gallon of gasoline contains around 6 pounds, or 125,000
Btus of energy in it. A gallon of hydrogen (gas) only contains around 40
Btus in it. Quite a difference!"

So, that storage system can store around 250 X ~40 Btu = ~10000 Btu =
about 3 kWh. So this is a capital cost of around $1850 / kWh for
storage. Much more expensive than the figure you quote (and stil not
includign installation or delivery)! But that storage unit works at
about normal atmospheric pressure and is small scale, and I would think
that a tank plus an electrolyzer should be much cheaper than that in
mass production (or if higher pressures are used)?

Note, if you look at:
http://www.thesolar.biz/Cost_Table_batteries.htm
lead acid batteries seem to have an initial purchase cost of around
$100-200/kWh but must be replaced (recycled) every 4-20 years (Depending
on the battery type). The advantage of hydrogen storage presumably is
that it does not have to be recyclced periodically -- although
realistically any tank might rust (although this is less of a recyling
problem than with batteries).

The big hopes for hydrogen storage seem to be things like carbon
nanotubes and metal lattices and so on.

The only gas turbines I've seen so far ("microturbines") seem desinged
to produce on the order of 100s of kW which is way to big for home use
(but not for a small community). Still I know research is underway to
make turbines on a chip and these will change the economics of this yet
again if put into production.

I think one of the biggest issues that I see remaining for SPS after my
discussion with TangoMan is that no matter how low the SPS operational
or capital cost can be made, SPS generated electricity still incurs the
grid operational and capital costs (now about $0.06 / kWh for around me)
which might even increase substantially if everyone uses the grid 3X
more than now (for home and industrial process heating needs) as then
the grid needs to be expanded in capacity. I don't see those costs going
down much because of the large amount of grid to be maintained in the
face of bad weather etc. But perhaps a better grid design or automated
underground cable laying might reduce such grid costs to SPSs benefit?

If you get more on operational cost figures for SPS I'd love to see
them! People keep implying they are near zero... Also, capital costs for
a grid expansion using today's technology to handle 3X or whatever more
power as likely if everyone uses SPS power exclusively would be nice to
know.

--Paul Fernhout