[extropy-chat] Nuke 'em
Robert J. Bradbury
bradbury at aeiveos.com
Sun Oct 23 15:22:17 UTC 2005
On Sun, 23 Oct 2005, Dirk Bruere wrote:
> If an efficient energy storage method could be developed eg electricty to
> methanol with >80% efficiency, then totally renewable becomes feasible. Even
> so, an electricity to hydrogen scheme coupled with a gas distribution grid
> may be sufficient.
I very much doubt you are going to be able to produce methanol from anything
with 80% efficiency. The obvious reaction would be something like methane
(natural gas) and water (CH4 + H2O --> CH3OH + H2). However methanol is a rather
nasty molecule to work with which is why ethanol is used as a fuel source
currently (Ford is actually pushing the fact that many of its vehicles will
currently run on gas or ethanol).
Someone would have to sit down and do the thermodynamics to see how much
energy would be required to drive the above reaction. It may simply be
that we don't have catalysts or enzymes that can drive this reaction.
There are *real* problems with an electricity to hydrogen scheme (which
can obviously be done through the electrolysis of water). The problem
is that hydrogen embrittles metal [1,2]. The entire current natural
gas pipeline system could probably *not* carry hydrogen without significant
safety risks and would have to be rebuilt/duplicated with pipes designed
to carry hydrogen. The last number I saw for that, and I think it was
a significant underestimate, was $100 billion.
The correct solution is solar ponds which produce methane (natural gas).
That uses the existing natural gas pipeline system and avoids the metal
embrittlement problem that hydrogen entails. Methane is *not* bad so
long as it is produced in a sustainable fashion. That requires that one
take the carbon out of the atmoshere (as CO2) and not out of underground
stores of natural gas (or methane derived from coal). There is nothing
wrong with burning methane so long as it is being done in a sustainable
fashion (i.e. any carbon you release back into the atmosphere came from
the atmosphere in the first place). It would take some large fraction
(~20% I think) of the land currently used for cattle grazing (note I
did not say farming) in the 7 SW U.S. states converted into solar
ponds (containing bacteria engineered to use sunlight to produce methane)
and you would have the energy equivalent of all U.S. oil consumption
(domestic production + imported). The construction of solar ponds is
very much a low-tech activity that could be done in a widely distributed
fashion. The income derived from methane producing solar ponds is also
significantly higher (probably by orders of magnitude) than that derived
from cattle grazing. The interesting thing is that all of the genes
required for methane producing photosynthetic bacteria are currently
sitting in public databases (though some clever engineering is required
to put them together properly... :-)).
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