amorphous pv & high voltage arrays [RE-wrenches]

[Matt Lafferty]

Wrenches:

Kent Sheldon wrote:
>
> > Some other things to watch out for
> > with amorphous is the larger Voc-Vpp voltage window and the larger
> > temperature derating than crystalline PV.
> >
Todd Cory wrote:
>
> I thought Asi performed better (less voltage degradation) when how over
> crystalline PV?
>
Kent is correct about the larger Voc-Vmpp window.   Asi also drops the
voltage in heat quite substantially.  The SB inverter does indeed have a
wide operating window and tracks amorphous very well.

Where Asi outperforms crystalline in the heat is in its Power Production.
Amorphous produces a significantly higher percentage of its rated power in
elevated temperature conditions than crystalline.  (I care a lot more about
Watts getting off the roof and into the grid than I do about Volts)

Here in the Sacramento Valley it gets quite warm.  I have done system
performance testing dozens of  times in the 105 - 108 degree F ambient
range.  I have never once had to factor in temperature correction to achieve
rated performance.

Crystalline, on the other hand, generally requires temperature correction
above about 87 degrees F.

If the array is configured correctly for the inverter voltage window in the
first place, the lower voltage under high temp conditions won't drop you out
of the operational window.

I would warn you about trying to configure an amorphous array for an
inverter with a narrow voltage window and also to calculate the true Vmpp at
about 8% lower than manufacturer rated for configuring your arrays.
Remember, the labels are at STC.  I'm still looking for my first STC
conditions in the field!

-Matt Lafferty
pvpro at attbi.com

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