Solar Panels

[Ted de Castro <tdc@xrayted.com>]

While on the subject of Solar Panels - or Photo Voltaics (PVs) I'd like
to see if anyone has hard information to settle a long standing
question.

Of course we all know that the Si industry has somehow avoided general
knowledge of the extremely corrosive and hazardous chemicals they use. 
That has already been mentioned here.

BUT - I once read that it takes more energy to produce a PV than it will
EVER produce!

Does anyone have the hard numbers on this?

Currently I am persuaded this may be so.  10 or so years a ago I did a
simple calculation at the surplus price of solar panels and the time to
payback from the electricity they generated.  The idea was that if
energy cost was a major part of the cost of producing a solar cell then
the time to cost recover from electrical generation alone would be very
long.  This was NOT meant to be a definitive calculation - but just one
for plausibility - certainly other factors can raise the cost. 
Conversely if the payback time was short - then obviously they could NOT
consume more energy than they could produce.

The payback time calculated to about 60 years.  Thus I concluded that it
certainly is possible that they COULD require more energy to produce
than they could ever put out.

More recently I had a project for a remotely cited monitoring station
where a PV was THE answer for power!  It is a temporary project and the
cost to get power to the site was high.

BUT - to design the project to be SURE the PV and batteries where right
to carry the load year round I had to do some calculations.  So - I did
a spreadsheet using actual hourly solar data for our site from the
previous year and calculated the charge state of the batteries hour by
hour.  This allowed me to choose between panel and battery capacity and
minimize cost.

The panel we use is a $615 120w crystalline panel.  An amorphous panel
would have been about the same price but 50% larger.

This panel was bought from Wind and Sun in Arizona - I found their web
site and excellent source of information (www.windsun.com).

They made the observation that PVs really haven't come down much in 20
years - and as for the future ....Their opinion is to "not to hold your
breath".  Pretty frank talk for someone making a living selling this
stuff!!  They also say that PVs NOW do produce more than it takes to
make them (but no hard data).

Anyhow - seeing this thread on alternative power sources I realized that
my spreadsheet designed to calculate battery charge could also calculate
total power output and I could redo the time to payback calculations I'd
scratched out before AND with current industry pricing for the largest
single PVs I could find.

Guess what - once again the answer was 60 years!!!

The guarenteed life of a PV to 80% capacity is 5 to 10 years depending
on the make and type (amorphous has a shorter life).

So - it is still plausible in my mind that the power to produce a PV
could very well exceed its life time generating capacity - or be very
close to it.

The argument is often made that PVs are too costly now for "normal"
installations - but as power costs go up - this will change.  BUT it is
obvious that if power is a major cost to make PVs - then their price
will go up accordingly.

Of course we could always wish for a new break through process that
makes them better and cheaper and more efficient.  But that is NOT here
and now - or even in the visible future AND has been "promised" for
almost as long as nuclear power has been said to become "too cheap to
meter".

Ted de Castro
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