On grid w/battery and MPPT [RE-wrenches]

[Doug Pratt]

Travis,

  We've been running the 10kW of grid-tied PV arrays at Real Goods Solar
Living Center at 60v with nine 6-volt batteries in series since we first
opened it in...what?...I think it was about '95. Works fine. We have a
nominal 48v system with 4 SW4048 inverters. It was probably on
Christopher or Robin's advice we went to 60v. I don't recall what the
exact settings are, but we're running in the 60 to 64 volt range.

-Doug Pratt

-----Original Message-----
From: Travis Creswell, Ozark Solar [mailto:ozsolar at ipa.net]
Sent: Wednesday, May 29, 2002 12:21 PM
To: RE-wrenches at topica.com
Subject: Re: On grid w/battery and MPPT [RE-wrenches]


Christopher and others,

I had this idea several years ago and wondered what you thought about
it.
Assuming one was to use a grid tie battery based inverter and 6 volt
batteries.  Instead of the standard battery bank that floated @ 53.6
volts,
use a battery bank that floated @ 59.6 by adding one more 6 volt
battery.
This also assumes that you can appropriately adjust the parameters of
the
float and bulk voltages.  Would this system produce more kWh's annually
since you were running the array closer it's maximum power point?  I see
that I can adjust the Float and Bulk voltages on my SW4048 up to 64.0.

Travis Creswell
Ozark Energy Services
----------
>From: Christopher Freitas  -  OutBack Power <cfreitas at outbackpower.com>
>To: RE-wrenches at topica.com
>Subject: RE: On grid w/battery and MPPT [RE-wrenches]
>Date: Wed, May 29, 2002, 11:51 AM
>

>Even in the alternate universe called California the performance of a
>system without MPPT will be different if the batteries are located in a
>conditioned space versus an exposed location as in Bill Brooks example.
>
>
>Another factor affecting the performance will be the nominal system
>voltage - a 48 vdc system will benefit more from a MPPT than a 24 vdc
>system for several reasons, which we can discuss more if people are
>interested...
>
>I am very interested in seeing performance comparisons testing of
>products by a third party - as long as the raw data is made available
>for review and a way to publicly comment on the results is provided
>(hint-hint).
>
>Christopher Freitas
>OutBack Power Systems, Inc.
>cfreitas at outbackpower.com  www.outbackpower.com
>Tel 360 435 6030  Arlington WA USA

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