[extropy-chat] cheap alcohol

[Eugen Leitl]

On Thu, Sep 22, 2005 at 02:36:15PM -0700, The Avantguardian wrote:

> Well thermodynamics pretty much guarantees you will
> waste a lot of joules no matter what you do. The

Not really. Solar collector efficiency can be 
quantitative http://www.solarserver.de/wissen/sonnenkollektoren-e.html

Rectennas can fundamentally work in solar spectrum
range http://www.nrel.gov/ncpv_prm/pdfs/papers/54.pdf
and can achieve efficiencies close to quantitative 
(has nothing whatsoever to do with Carnot efficiency).

What this effectively means that (at least outside
of murky gravity well and high enough to be mostly 
unshaded) you can get ~1 kW/m^2 around the clock.
A km^2 buys you 10^9 J/s. Miscanthus is ~10^11 J/km^2/year.
A year has 10^7 seconds. (Check the math, I might
have dropped a zero or two).

> joules the bugs use to keep alive, I think would be
> pretty efficient compared to the heat loss in most
> chemical processes. Moreover, they should be able to

89% DIN wood pellet burner efficiency.
http://www.iea.org/textbase/papers/2005/ETOAltFuels05.pdf
claims 50% biomass conversion efficiency as energy.
Heat-electricity coal plants have 40-50% combined 
efficiency.

> extract all their energy needs right from the input
> biomass. The beauty of bioreactors is that they don't
> require lots of input energy to get over any
> activation energy humps. There will still need to be
> some though, to grind the biomass into tiny little
> bits to maximize surface area exposed to the bugs.

I like bioreactors. The problem is that the bugs
are finicky, and inefficient, and you'll get
plenty of liquid/solid waste.
 
> This sounds fairly cool, is it n-hexane or
> cyclohexane? The two extra hydrogens on n-hexane would
> make for slightly more energy output upon combustion. 

IIRC n-hexane, but I can't find the paper right now.
I think it was in Science.
 
> > A low-tech version would just pellet the straw,
> > and use a modern pellet burner. 
> 
> Well this doesn't sound very clean. I don't how you

No, new wood pellet burners are quite clean
http://hearth.com/what/pellet/pellet1.html

> would power an engine with a pellet burner except for
> a return to steam engines. And we would have a huge

Nondomestic use would be gasification or synfuel, and
gas turbine, or high-temp fuel cell.

> brown cloud hanging over our heads the way the Chinese
> do. 

No, though methane or hydrogen would be cleaner, of course.
 
> > Do you have a working process prototype, or are you
> > just thinking of starting to develop one?
> 
> No, although I have had the idea for years, it hasn't
> progressed much further than a few schematics in my
> notebook. Developing it further would require a bit
> more time and money than is afforded by being a
> graduate student. But things change and I may get a
> shot at building one in the next few years.

Good luck!

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a>
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ICBM: 48.07100, 11.36820            http://www.leitl.org
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