Xantrex versus Sunny Boy [RE-wrenches]

Bill Brooks billb at endecon.com
Fri Aug 1 11:40:05 PDT 2003


Kent,

We will soon know what the transformer losses are since we will be testing
two PV20208 inverters next to 10 SB2500 inverters. The SunnyBoys have a
clear advantage with nighttime losses and the advent of the HU361RB being
able to handle three inverter greatly simplifies the installation. We will
be taking a close look at all these issues and if I'm wrong on the overall
energy conversion issue, I will gladly repent.

It is not a simple decision one way or the other. There are so many factors
that could sway the decision either way so I don't think Marco's question
has a clear right answer. I think he would do well with either a PV30208 or
12 SB2500 inverters.

Marco's original question dealt with the fact that he owns a PV30208--if it
were me, I would install it because there is not a clear enough benefit to
leave that inverter in stock and go out and buy a bunch of new inverters.
Maybe on his next project he can try a bunch of SunnyBoys and write up his
results for us all.

Bill.




-----Original Message-----
From: Kent Sheldon [mailto:kentsheldon at sbcglobal.net]
Sent: Sunday, August 31, 2003 10:14 AM
To: RE-wrenches at topica.com
Subject: Re: Xantrex versus Sunny Boy [RE-wrenches]


The SC125 was created for the very large PV systems being installed by
utility companies to fulfill their green power portfolios. They generally
install MW size plants in remote locations, so real estate, orientation,
access, etc. is not an issue. We also realize some installers prefer to use
one inverter to keep initial installation costs as low as possible, which
IMHO is a poor strategy.

Regarding the crossover point between SC and SB inverters, I think the SC125
will be better than Sunny Boys when you have a commercial installation with
500kW up to MW of PV in the same orientation and configuration. I have
always been a proponent of inverter redundancy, even when I was working at
X-Co. If any of you asked my opinion then, I would recommend 4-10X inverter
redundancy on any system for the same reasons stated previously in this
thread.

I disagree with Bill's positions that SB's cannot come close on cost. For
some reason the punch line from SNL's Point-Counterpoint with Chevy & Jane
comes to mind. Jane.... you are not considering the after-sales cost
benefits that the SMA products offer. Nor do I agree with his assessment of
overall system efficiency being equal. Instantaneous operating efficiencies
will be similar, but the external isolation transformer will consume the
equivalent of 6-10% (transformer dependent) of produced PV energy when the
inverter is off-line. Remember, VAR is current, being charged to the
customer, just like Watts. Figure out how much it would cost to add that
much more PV to offset the night-time transformer losses. I recently ran
some numbers on a 112kW system, and came to $45K worth of PV, installed
cost, using a relatively efficient external isolation transformer.

Best regards,



___________________________________
Kent Sheldon
Projects Manager, Industrial Power Systems
SMA America, Inc.
530 273 4895 ext 107

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