Re: [energyresources] Re: PV modules made from scrap silicon
>The computer chip industry makes silicon or SiAs crystals with highI think in the past the size of the photovoltaic industry compared to
>precision and low tolerances for flaws. Further, you end up with a chip
>that is the size of a postage stamp or a small tile. So the total amounts
>of silicon produced by the computer industry is actually not that large.
>In order to have large scale PV generation we are talking about a net area
>on the order of square kilometers of wafers. If PV production becomes
>large it simply could not rely upon the seconds from the INTELs et. al..
>So ultimately a PV industry would have to generate its substrates from raw
>Lawrence B. Crowell
the semiconductor industry was small so that there were comparatively
a lot of sliced wafers that were not up to the very demanding chip
making specs, and its pretty easy to make efficient PV cells out of
these -- until the supply of junk wafers is tapped out.
But there is a whole new range of possibilities for polycrystalline
and ribbon based silicon cells that are pretty good -- but that don't
take all the effort of making large silicon boules and slicing them
up to make the large perfect crystals needed to make conventional
chips. But in this realm, the techniques have not been perfected
through research and manufacturing experience to optimize the various
possible approaches. The best thing about variations on this
technique is that crystalline silicon is formed at a high temperature
and thus the doping impurities are locked-in to a rigid, stable
crystal structure, meaning that such cells are unlikely to degrade
over time, and could last for centuries if shielded by glass.
On the other hand the evaporated thin film silicon-germanium
multi-layer cells like those recently produced by Ovshinsky's Energy
Conversion Devices are cleverly engineered multi-layer, multi-bandgap
amorphous cells and these amorphous structures are efficient and
potentially cheap and thus promising but tend to degrade somewhat
over time. But this is still a leading approach for making acres of
cheap cells for covering roofs, etc.
I think that copper/cadmium indium selenide cells have a weakly
bonded crystal structure formed at lower temperatures in which dopant
diffusion over time might well also cause ageing problems. But such
thin layer cells tend to be cheap to make due to the small amounts of
exotic materials used.
I would guess that any cells that have an organic dye sensitizer and
liquid electrolyte component like the TiO2 cells would be be likely
to degrade over time.
Few organic dye molecules are very resistant to prolonged exposure to
UV, although I think phallocynanine (sic) dyes are. -- Roger
Don't know if my reply to the person who asked about long-term effects
and dangers of geothermal development in NW N. America got through.
Just in case it did not -
Close at hand, Yellowstone/Old Faithful predictablilty has been
recently altered. This may be due to underground nuclear blasts,
or movements of plates, or other factors.
Iceland has used geoth without a halt, and with few reported problems,
for a looooong time.
I will CC this to the International Geothermal Assoc., and members
of considerable knowledge and experience may address the question
by replying back (to me svp).