amorphous pv & high voltage arrays [RE-wrenches]

[Matt Lafferty]

Joel / Wrenches:

Joel Davidson wrote:

> I installed 688 kW AC of single crystal PV in SMUD territory between
December
> 1994 and September 1996. I think single crystal annual energy production
is
> equal or better than amorphous if you compare DC STC single crystal
"apples to
> apples" of DC STC amorphous (not DC PTC or AC). What have you seen?


Wow!  What a perfect question!  You know what?  I don't honestly
know.....yet.  We are going through the whole process of complete
documentation, data compilation and then analysis right now.  (Quite an
undertaking, as you especially can imagine)  I don't know when all this will
be complete, but it will be quite interesting to read, for sure.

Our answers will be based on annual AC kWh yield per rated kWAC installed at
what orientation or combination of orientations, what slope, with how much
annual shade.  The data will be further broken down into which modules were
installed with which inverters.

I can tell you that we have done "out of the box" and "installed for 6
months" and "installed for 3 years" testing on a number of single crystal
modules....In general, most met the spec sheet fine print stating "plus or
minus 10%"....Sorry to say, none of them were "plus".  Most results were
more like 7 -8% below nameplate.  No significant degradation over the time
periods tested.

Our comparable testing of amorphous has shown sharp wattage degradation in
the first 6 months then stabilized to about 15% max below the "out of box"
initial IV curves.  Post stabilization results have been level.  The
advantage to the amorphous has been that the "out of the box" results have
been high enough above the nameplate ratings to compensate for this.

We will have some Real World comparative data in the not too distant future.
By this fall, I hope.  Will be happy to share when it's done.

-Matt Lafferty
pvpro at attbi.com

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