So if I understand you, your problem is that you have a grid tied battery backed system XW based system that ought to be exporting power. I have installed the same system near my office. You are finding that the customer's electricity cost has not decreased as expected.<div>
I know that when I stand in front of the utilities mechanical meter at noon, especially when the owners are not in residence, the meter spins backwards at a rapid pace.</div><div><br></div><div>In order to make that work, I programmed the inverter to a "Charge Off" setting. I let the batteries charge by solar only.</div>
<div><br></div><div>The XW is a pig to setup , I used the outback GFX seriesafter that installation.</div><div><br></div><div>The biggest issue is the hybrid setups like this have poor reporting so it is hard to know what is going on without moving in. In your case, I would put one of my eGuage metering units on the utility feeder and look at the export and import in real time. I would also put CTs on the inverter feed to measure the production and consumption. Let me know if you need help with that, I resell these devices.</div>
<div><br><br><div class="gmail_quote">On Mon, Apr 16, 2012 at 10:56 AM, William Miller <span dir="ltr"><<a href="mailto:william@millersolar.com">william@millersolar.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
Chris:<br><br>
I would willingly clarify but I am confused about what you are confused
about. I think we are saying the same thing about off-grid
systems: If you don't consume power, battery voltage stays high and
charge controllers reduce energy harvest.<span class="HOEnZb"><font color="#888888"><br><br>
William Miller</font></span><div class="im"><br><br>
<br><br>
At 06:57 AM 4/16/2012, you wrote:<br>
<blockquote type="cite">William,<br>
I must confess to being totally confused by your post.<br><br>
I am currently at my office writing to you using electricity from our
off-grid solar system. We only have the solar power, no grid
power.<br><br>
We get exactly as much power as I predicted we would, in fact a little
more. But, there is an intrinsic issue with off-grid systems that many
people miss. Unless you have a use for the power, it won't be
"harvested". If you allow the inverter to charge the batteries
from the grid, there will be nowhere for the PV power to go.<br><br>
To give you an example, our warehouse and office has 2,580 watts of PV on
a 60 amp charge controller and a 3.5KW outback inverter, with 250Ah of
VRLA batteries (4 x 12V).<br><br>
Each day, I read the amount of power the charge controller makes. It
averages about 12KWh, depending on how much we used that day and the
state of the batteries at the beginning of the day. We have found that
the loads did not adequately exploit the power product capabilities of
the system, so we moved our freezer from the house to the warehouse to
use up some more power.<br><br>
As we are in the Caribbean, the insolation levels are pretty continuous,
so it does make calculations easier.<br><br>
<br>
Chris<br><br>
<br><br>
On Mon, Apr 16, 2012 at 1:50 AM, William Miller
<<a href="mailto:william@millersolar.com" target="_blank">william@millersolar.com</a>>
wrote:<br>
<dl>
<dd>Friends:<br><br>
</dd><dd>There has been recent discussion on this forum about PV production in
grid-tied with battery systems. I have been faced with this same
problem in a 3 XW system installed in 2009.<br><br>
</dd><dd>The customer's power bill never went down. PV harvest was
abysmal. The system would create great short circuit current but
would not harvest into the batteries.<br><br>
</dd><dd>It is starting to appear the XW firmware was at fault. The
inverters would charge the batteries too high so the charge controllers
would back off. Upgraded firmware seems to be helping, but the data
set is still limited.<br><br>
</dd><dd>Remember this: just because a PV system can produce does not
mean it will. The charge controller knows only one thing:
battery voltage. If it is high, production is curtailed.<br><br>
</dd><dd>Off-grid production will also be reduced is consumption is
curtailed.<br><br>
</dd><dd>Charge controllers that can be set for grid-tied applications help,
but only if the inverter(s) do not keep the battery voltage too
high.<br><br>
</dd><dd>William Miller<br>
</dd></dl></blockquote></div></div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br>Chris Mason<div>President, Comet Systems Ltd</div><div><a href="mailto:masonc@cometsystems.co" target="_blank">masonc@cometsystems.co</a></div><div><a href="http://www.cometsystems.co" target="_blank">www.cometsystems.co</a></div>
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