[extropy-chat] Solar math (was: Nuke 'em)

Dirk Bruere dirk.bruere at gmail.com
Wed Oct 26 20:17:26 UTC 2005

On 10/26/05, Russell Wallace <russell.wallace at gmail.com> wrote:
> On 10/26/05, Eugen Leitl <eugen at leitl.org> wrote:
> >
> > So we don't even need those 1.2%. Can you crunch through
> > the numbers, assuming 100 kWh for 1 m^2/year (at 10% efficiency,
> > half that at 5% efficiency)?
> Let's take 10%, solar panels or heat engines give you maybe 20-30% but
> much of it will have to be stored and recovered so you'll take losses there.
> 100 kWh/year works out to average 12 watts delivered, which sounds like a
> plausible figure for cloudy northern climates. Say 5 kW/person (I've seen it
> quoted that Americans use 10 kW, but presumably they do that because it's
> cheap, and would cut back if it stops being cheap). That's 400 m^2, or a
> square 20 m on a side. You won't get it all from rooftops alone (though
> rooftops might supply a lot of domestic usage), but it's not a huge amount
> compared to total land use, so at the end of the day switching everything to
> solar looks doable (though not cheap) with present day technology.
> Depends what 'cheap' means.
Given our present 'uneconomic' PV tech, how much would five years worth of
half the US military budget buy (say, round about $1t)?

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