PV Inverters module strings (Last Call) [RE-wrenches]

Joel Davidson joeldavidson at earthlink.net
Thu May 10 14:51:04 PDT 2001


Thanks for the input.

Bill Brooks wrote:

> Carl and Joel,
>
> >From their website:
>    US-64
> Rated Power (W)   64
> Operating Voltage (V)   16.5
> Operating Current (A)  3.88
> Open Circuit Voltage (V)   23.8
> Open Circuit Voltage (V)  @-10 deg. C and 1250 W/sq. m   27.1
> Short Circuit Current (A)  4.80
> Short Circuit Current (A)
> @ 75 deg. C and 1250 W/sq. m   6.30
> Series Fuse Rating (A)   8.0
> Weight (lbs/kg)  20.2/9.17
> Height (in) 53.78
> Width (in)   29.18
>
> This shows that max Voc is 27.1 Volts @-10 deg. C and 1250 W/sq.
>
> Dividing this number into 600V we get 22 modules in series. The voltage
> derating is not stated so I would guess, based on experience with these
> products that their Vmax will vary from 350-365Volts in the summer. This is
> on the low end of the Trace Tech inverter, but should work. I would feel
> much better with more data.
>
> Unfortunately, as arrays degrade, they lose voltage, so this array will
> eventually go to low enough voltage that it will be well off of the max
> power during hot weather.
>
> A better inverter for this module might be the SMA SunnyBoy. It has a wider
> input voltage. John Berdner might disagree with me on this, but I would
> suggest always putting the maximum number of modules in series on the SMA.
> The reason for this is all PV arrays degrade in Vmax, so it is better to
> start the array at the highest possible voltage so that as it degrades, the
> inverter can handle the lower voltages. If you put a lower number of modules
> in series, you may eventually have voltage problems.
>
> So, in places where it never goes below 0 degrees F during the day, 22
> modules in series is the maximum to stay under the 600 Volt limit of the
> module.
>
> Bill.
>
> > -----Original Message-----
> > From: Carl Emerson [mailto:freepower at freepower.co.nz]
> > Sent: Wednesday, May 09, 2001 6:53 PM
> > To: RE-wrenches at topica.com
> > Subject: Re: PV Inverters module strings (Last Call) [RE-wrenches]
> >
> >
> > Dear Joel,
> >
> > I have Emailed Qudrat Delawari at Unisolar for the data needed to
> > consider the
> > suitability or otherwise of the Unisolar roofing products and the US64.
> >
> > If someone else already has this, please speak up....
> >
> > Regards,
> >
> >
> > Carl Emerson
> > Manager
> > FREEPOWER LTD.  "Harnessing Natural Energy"  Auckland, NEW ZEALAND.
> >
> > Joel Davidson wrote:
> >
> > > Dear Carl,
> > > Thanks for the useful information which will be incorporated in
> > the compiled list.
> > > Perhaps someone from Uni-Solar or another designer using
> > Uni-Solar would like to add
> > > their perspective.
> > > Best regards,
> > > Joel Davidson
> >
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