ST versus Sunny boy [RE-wrenches]

[Solar Technologies]

This result is what we have also seen in the field, but without quite the
thorough regimen of testing that Bill used.  In our case, we're using a 24
panel string of Kyocera KC120s, which produced about 2100 watts max from the
Sunny Boy at solar noon in coastal California.  Noteworthy is that they also
were still producing 1000 watts at 4 PM under fairly heavy fog.  (Evidence
of good MPPT software.)  We would add one more observation of the comparison
of the ST to the SB:

The STs appear to produce a significant amount of RF interference in the
lower AM radio band
No such interference was noted in the SB

Roger DeNault
Solar Technologies

----- Original Message -----
From: "William Miller" <wrmiller at slonet.org>
To: <RE-wrenches at topica.com>
Sent: Monday, August 13, 2001 9:59 PM
Subject: ST versus Sunny boy [RE-wrenches]


> Pals:
>
> Earlier I had written about some ST inverters that I thought might be
> providing low output.  It was asked that I provide more information on
> array, location, etc.  I investigated more thoroughly, measuring
> insolation, input current and voltage versus output current and voltage.
> During this process I gained access to the Sunny Boy 2500 watt inverters.
> I had a chance to perform a "side-by-side" comparison today--at least as
> close as side to side as one can.  I had the Sunny Boy installed and was
> able to switch over to the ST in about 40 minutes.  Here are the results:
>
> Array: 24 Siemens SR100 panels on two fixed, top of pole racks.
> Azimuth: Approx. true south
> Tilt: Approx. 16 degrees
> Temperature: Approx. 70 degree F
> Output Amp measurements: Averaged over 5 minutes with a Fluke 87 on one
> pole of 2 pole output breaker.
> Input amp measurements: Averaged over 5 minutes with a Fluke 87 on input
DC
> lead (after combiner for ST)
> Array and AC voltage measurements: Beckman DVM
>
> Results:
>
> SB2500:
> 8/13/01 1:10 pm
> 7.00 avg @ 242 v ac (1, 694 watts)
> Insolation: 45 w/m2
>
> ST2500:
> 8/13/01 1:53 pm
> 6.31 @ 245 v ac (1, 545 watts)
> Insolation: 45 w/m2
>
> As you can see, the SB is about 10% better.
>
> I would note these other differences:
>
> The SB is quieter (no fan)
> The SB is string wired (smaller wire size, more flexibility where to
locate).
> The ST has input and output and GFI breakers built in.
> The ST has metering built in.
> The SB offers optional remote metering and free monitoring and control
> software.
> ST clients are complaining about the ST shutting down periodically
> throughout the day, even after installing the latest chip upgrade.  One
> client found that after the chip upgrade, his system stopped shutting
down,
> but the output dropped by about 10%.
>
> Any suggestions on testing procedures and any questions are appreciated.
>
>
> William Miller
>
> PS: I also checked efficiency of both inverters, comparing input watts
> against output watts.  They both range about 90%.  I can only surmise that
> the higher output on the SB is because it has a better MPPT circuit (loads
> the panels better).
>
>
> WM
>
>
>
> __________________________________________________________________
> William Miller
> SLO Communications: Communications and Power Systems Consulting
> PO Box 50, Santa Margarita, CA 93453
> Voice :805-438-5600 Fax: 805-438-4607 VMail: 805-546-4875
> email: wrmiller at slonet.org
> License No. C-10-773985
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> __________________________________________________________________
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