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

[Eugen Leitl]

On Wed, Oct 26, 2005 at 03:46:17PM +0100, Russell Wallace wrote:
> > http://www.eere.energy.gov/solar/pv_cell_light.html says it's about 6
> > kWh/m^2/month
> > insolation, for U.S. June.
> 
> 6 kWh/m^2/month? That can't be right. Suppose average insolation is only 100

Hey, I saw it on the internets, so it must be true.

> W/m^2 (probably an underestimate for June); there are 720 hours in a month,

In vacuum with 100% insolation at 1.35 kW/m^2 a m^2 receives some 1000 kWh/month.
Best case Earth surface (no clouds, vertical insolation) is 1 kW/m^2,
so with a 6 h day you'd get some 190 kWh.
September in Germany is about 100 kWh/month according to 
http://www.solarserver.de/service/strahlungsdaten.html 
so http://www.eere.energy.gov/solar/pv_cell_light.html is
bogus, and all my data based on it. In fact http://www.solarserver.de/pvrechner/index.php
even gives 97 kWh for 1 m^2 for a year at 10%, which makes me think that
those 6-8 kWh/month cited are real output of a PV panel at 10% efficiency,
and not just insolation.

Good catch, somebody is actually reading these mails.

> so that would make the monthly insolation 72 kWh/m^2/month.

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)?

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a>
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