amorphous pv & high voltage arrays [RE-wrenches]

[Joel Davidson]

Matt,
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?
Best regard,
Joel Davidson

Matt Lafferty wrote:

> 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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