[extropy-chat] Nuke 'em

[Eugen Leitl]

On Sun, Oct 23, 2005 at 04:12:19PM -0700, Damien Sullivan wrote:
> On Sun, Oct 23, 2005 at 11:01:39PM +0200, Eugen Leitl wrote:
> 
> > I don't see why everyone is hypnotised by efficiency. It's just a yet
> 
> Because for the whole human population we're talking about coating much of the
> planet with power collectors and while there may not be a huge difference
> between .1 and 1% there's a big one between 10% and 100%.  Or 30% and 300% of
> the planet...

http://www.eere.energy.gov/solar/pv_cell_light.html says it's about 6 kWh/m^2/month 
insolation, for U.S. June. At 5% efficiency, a 60x60 m would be about enough for
the average 2005 household http://www.eia.doe.gov/emeu/reps/enduse/er01_new-eng.html
(notice that's *one third* of that in Germany at 333 kWh/month, so 30x30 m should 
have been enough -- something is running quite wrong on your side of the pond).

12% of Germany land area is covered with artificial structures, that's about
42843 km^2. At 5% efficiency that's 257058000000 kWh, or enough energy for
771251125 people. As there are only 82.5 Mpeople, it would be enough to use
1.2%, one tenth of the entire covered area. At 5%, which is current efficiency
for anorganic and hybrid organic solar cells. 

--> The planet needs not to be paved more than it is already, a fraction
of area covered converted will already do.
 
> > > And what are the thermodynamics of getting CO2 from 300 ppm to 100,000 ppm
> > > or whatever the C concentration in biomass would be?
> > 
> > Plants are nanotechnology, so it works for them. Unfortunately, trees have
> > no power sockets in them, nor do they grow on demand whatever you just
> 
> Uh, hybrid system, Eugene.  Hydrocarbons were for transportation purposes.

My point was that plants don't directly produce hydrocarbon fuels.

> Things which need power sockets would be fed directly from the photovolatic
> grid, ideally, except of course that needs buffers of some sort for when the
> sun don't shine.

Electrolysis/fuel cell and pressurized storage would be about ideal here.
 
> > minimum. Can you imagine an evolutionary process resulting in nonprotic 
> > photochemistry? Why are plants not velvet black in the first place?
> 
> Perhaps they're already using all the energy they can limited by other factors
> and they don't want to cook?

Can you imagine an evolutionary process resulting in a plant that can operate
at 130 C, normal pressure?
 
> > > Which is why a solar heat engine can produce electricity better than a
> > > photovoltaic, at least in direct light.
> > 
> > Uh, I'd like to see your Stirling beat 35% efficient (theoretical
> > plateau around 55%) solar cell.
> 
> I'd heard 50% for heat engines and 30% for PV.  If it's the other way around,
> fine.

http://www.visionengineer.com/env/fc_efficiency.shtml
Solar-heated medium for Stirling is cold, so your efficiency is low.
Adding mirrors and tracking makes the problem actually worse. Won't 
work with diffuse daylight, either.

-- 
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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