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Ray,<br>
<br>
The balancing transformer isn't allowed with the GVFX inverters. In
a dual FX inverter system, using the balancing transformer or not
using it is nearly a wash. I think you save 15 watts when the
inverter is asleep but the transformer losses are 10 or 12 watts.<br>
<pre class="moz-signature" cols="72">Kent Osterberg
Blue Mountain Solar, Inc.
<a class="moz-txt-link-abbreviated" href="http://www.bluemountainsolar.com">www.bluemountainsolar.com</a>
t: 541-568-4882</pre>
<br>
On 1/5/2012 1:33 PM, Ray Walters wrote:
<blockquote cite="mid:4F061734.3030805@solarray.com" type="cite">
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I have a related question to this. Does setting up a pair of
Outback GVFXs with the balancing transformer and allowing one
inverter to go to sleep at lower AC output improve efficiency? It
seems we would be reducing electronic loads, but adding
transformer losses. Any comments? I have a recently commissioned
double Outback system with 200 AH @48v battery bank. He's
reporting efficiency at 77% DC in to AC out. I'd love to improve
that, as his aging array of Sharp modules seems to be under
performing as well, (4.08 KW STC rated, 3 Kw actual out) I
haven't gone back and done testing with my insolation meter, so
I'm not sure exactly what is happening, but his overall efficiency
(STC rated to AC out) is only 56% .<br>
<br>
Ray<br>
<br>
On 1/4/2012 7:55 PM, Maverick Brown [Maverick Solar] wrote:
<blockquote cite="mid:A4F08B3A7C2746219FA24FD632D8CB46@MSE002"
type="cite">
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<meta name="GENERATOR" content="MSHTML 8.00.6001.19170">
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">Please use the 90%
of the CEC or PTC rating of the PV module at most.</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">Among
several systems that I monitor daily, I have an
example 11.760kw (STC) system that has a 500Ah battery
bank and it peaks at 77-80% of the STC rating each day.</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">Peak is defined as
the top of the bell curve that forms from the graphing
watts output versus nameplate watts.</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">If I use the CEC
rating (10.54kw), it peaks at 86-90% of the CEC rating
each day.</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">If I go to the CEC
list and copy & paste into a spreadsheet and enter the
values for the STC versus PTC, I <em>might</em> find I
would loose 10% (or more) in the PV rating.</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2"><a
moz-do-not-send="true"
href="http://www.gosolarcalifornia.org/equipment/pv_modules.php">http://www.gosolarcalifornia.org/equipment/pv_modules.php</a> (go
ahead, find your modules and divide PTC by Nameplate).</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">I also have a
grid-interactive system that has a very large battery bank
(2600Ah @ 48V, with 9kw STC Array) and it only has a peak
efficiency rating of 69% because of the load of the
batteries. The larger the battery bank, the happier
customers are for outage situations, but the larger the
battery bank, the more current goes into "Floating" the
batteries during selling. For that system, I may lower
"Grid Support/SellRE" and use Auto EQ to keep the
batteries fresh...</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">Anyway, keep in mind
that you cannot simply assume:</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">12kw Array x 6 hours
of sun = 72kwh of generation each day. The brand of PV,
the size of the battery bank and even the charge
controller's Absorb & Float settings can greatly
reduce what the inverter thinks it can sell. With multiple
inverters and charge controllers it gets even more
complicated (worse).</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span><span
class="683282302-05012012"></span><span
class="683282302-05012012"><font color="#0000ff"
face="Arial" size="2">Good luck,</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"><font
color="#0000ff" face="Arial" size="2">Maverick</font></span></div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<div dir="ltr" align="left"><span class="683282302-05012012"></span> </div>
<br>
<div dir="ltr" class="OutlookMessageHeader" align="left"
lang="en-us">
<hr tabindex="-1"> <font face="Tahoma" size="2"><b>From:</b>
<a moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]
<b>On Behalf Of </b><a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:boB@midnitesolar.com">boB@midnitesolar.com</a><br>
<b>Sent:</b> Wednesday, January 04, 2012 5:14 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] DC to AC derate<br>
</font><br>
</div>
On 1/4/2012 3:01 PM, All Solar, Inc. wrote:
<blockquote
cite="mid:B5CBE3E26B764CC9987DB55BA8FD7972@SrvcTagGV13VB1"
type="cite">
<meta name="GENERATOR" content="MSHTML 8.00.6001.19088">
<style></style>
<div><font face="Arial" size="2">Wrenches,</font></div>
<div><font face="Arial" size="2">Once again I am trying to
size a grid tie w/battery system and I struggle a little
with the efficiencies of them.</font></div>
<div><font face="Arial" size="2">With PV Watts (v.1), is
changing the DC to AC derate an accurate method for
getting the output?</font></div>
<div> </div>
<div><font face="Arial" size="2">Thanks in advance!</font></div>
<div> </div>
<div><font face="Arial" size="2">Jeremy</font></div>
</blockquote>
<br>
<br>
If you keep the batteries charged to a voltage just above their
resting voltage,<br>
say, 52 volts for a 48V system, and the battery bank isn't too
large, (~225 A-hours,<br>
maybe a bit more), about 90% PV to grid AC efficiency is in the
ball park.<br>
<br>
That's what we figured in the early days of GFX inverters at
OB. That's giving<br>
5% for the electronics and 5% for keeping up the batteries.<br>
Different and/or more accurate information may have come along
since<br>
that time.<br>
<br>
boB<br>
<br>
</blockquote>
<br>
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