Solar Ideas - long but hopefully informative

[Andreas Georgiades <AGeorgiades@Gain.com>]

I've been considering buying a PV (photovoltaic) solar panel system but I
was pretty shocked at how significant the initial cost would be...
I thought, oh well, once you buy it should pretty much pay for itself  in a
few years assuming it's virtually
maintenance free.
So, I visited the Tucson Electric Power website to get a rough estimate for
rates. The rates are frozen till 2008 after 3 consecutive
decreases in the past 2 years.
Roughly the rates for a home are about 10cents/kWh (more in the summer, less
in the winter)

Now, let's take a simple 100W PV Solar Panel:
In Tucson (virtually, the sunniest city in the US) I'll assume 6 hours of
full sun per day

Therefore, my single panel will produce 600Wh of power ( 0.6kWh a day, the
equivalent of 6 cents (!!!) of electricity.
A solar panel alone goes for roughly $5/W so my investment would be $500 for
a single 100W panel.
Not only that, but I'm also assuming 100% efficiency on the inverter side
(80% is more likely)

This tells me that it would take ( $500 / $0.06/day = 22 YEARS!) to
recuperate the panel cost alone not 
to mention the cost for storage batteries, inverters, cable runs, various
electronic systems that would track the sun,
limit any shorts, warn for low batteries, etc. etc. etc.)

Environmental Cost
----------------------------
Many people innocently assume that since a solar panel produces very clean
power (and it does) its
overall environmental cost is zero. On the contrary, the solar cells are
silicon wafers and are submitted to 
the same processing as semiconductor chips (I work in this field although
not in fabricating). There are dozens 
of noxious gases and substances that are used in processing of the solar
cells (arsenic is one that springs in mind, also
all sorts of acids (HCl , H2SO4, HNO3, etc. etc.)). Therefore, the
enviromental cost in producing these products is definitely not
zero and needs to be considered in the whole equation.

Any Si wafer gurus out there?

More Calculations
--------------------------

In order to power a decent size home off-grid (3bdr - 5 people) I'll assume
a daily need of 24kWh [that corresponds to ~$2.40/day, my family
unfortunately spends 3 times that...] per day (assuming it's evenly spread
over 24 hours which is definitely not). 

If you have not been lost yet in all the nested parentheses, I admire your
power of concentration... :)

Anyway, also assuming that we get only 6 hours of full sun per day, the PV
system needs to provide into storage (batteries) power for the 
remaing 18 hours of the day. therefore, the PV system needs to produce 24kWh
in 6 hours. That's a 4kW solar panel system!
It's 40 panels of 100W power ( 40 * $500 = gasp! $20,000) + inverter
=~$4,000 + batteries =~$500/$1000 + etc. etc.
It can be seen that  the initial cost can easily exceed $25,000

Say, a grid connected house was using power irresponsibly as opposed to an
off the grid house where people
will tend to be much more thrifty/responsible.
It is not unreasonable to assume that a grid connected house will spend
~$100-$150 a month (like ours).
Therefore, a $25,000 investment would pay itself off within 150-250 months
(12-20 years).
And that's assuming zero maintenance (highly unlikely)

After all these calculations, does a solar panel system even make sense
unless its initial cost
is dramatically reduced or grid-power rates are dramatically increased?
(hello California!)


Any ideas out there from all you supersmart people from all over the world?

Andreas 
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