From: Eugene Leitl (eugene.leitl@lrz.uni-muenchen.de)
Date: Sun Sep 03 2000 - 13:02:25 MDT
hal@finney.org writes:
> A quick web search found an article with interesting claims.
> http://whyfiles.org/041solar/main1.html is about the Sacramento Municipal
> Utility District installing a large photovoltaic system:
Large photovoltaic installations do not really make sense. Especially,
if one wants to avoid transforming the power to grid level, and use
the 12-24 V (which can't be transported beyond a few meters because of
high losses) directly (camping gear type small installations).
> One caution I've heard with regard to renewable energy, is that
> sometimes the energy costs to produce the equipment (the PV cells and
> such) are actually greater than the energy produced by the machinery
> over its lifetime. If the initial manufacturing costs are supplied by
> nonrenewable sources then the net effect is negative.
Of course, this is an old argument, often brought forward against
nuclear energy by polemical types.
Let's assume a 1 m^2 PV panel, with the average insolation of 0.5
kW/m^2. Let's say the efficiency is 10%, so it generates 0.05 kW (50
W) on the average. Let's say we do get 10 years effective life time
out of it, with ~10 h hourly insolation. We're getting 10 y * 365 d
*10 h =36500 hours, at 0.05 kW. This is rougly 2 kWh, right?
Hmm, unless I made a mistake, that's a bit low. Anyone has real world
numbers, both for mono and polycristalline (and amorphous) cells?
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