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

[Bill Brooks]

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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