<br><font size=2 face="sans-serif">Hi,</font>
<br><font size=2 face="sans-serif">That is correct...the XW does have a
frequency shift (Batt V=Bulk) that causes grid-tie inverter to disconnect.
Remember, the </font>
<br><font size=2 face="sans-serif">total kW of the grid-tie unit cannot
exceed the rating of a single XW, even in a multi-unit system.</font>
<br><font size=2 face="sans-serif">Eric<br>
</font><font size=3 color=#008000>_____________________________________________________________________________________</font><font size=3>
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</font><font size=1 face="Arial"><b><br>
Eric Bentsen</b> | </font><font size=1 color=#008000 face="Arial"><b>
Schneider Electric </b></font><font size=1 face="Arial"><b> | Solar
Business</b> | <b>UNITED STATES</b> | <b>Technical
Support Representative</b> <b><br>
Phone:</b> +(650) 351-8237 ext. 001# | <b><br>
Email:</b> </font><a href="mailto:eric.bentsen@schneider-electric.com"><font size=1 color=blue face="Arial"><u>eric.bentsen@schneider-electric.com</u></font></a><font size=1 face="Arial">
| <b>Site:</b></font><a href="http://www.schneider-electric.com/solar" target=_blank><font size=1 color=blue face="Arial"><u>
www.schneider-electric.com/solar</u></font></a><font size=1 face="Arial">
| <b>Address:</b> 250 South Vasco Rd., Livermore, CA 94551
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<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">From:</font>
<td><font size=1 face="sans-serif">Ryan <ryan@kb1uas.com></font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">To:</font>
<td><font size=1 face="sans-serif">re-wrenches@lists.re-wrenches.org</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Date:</font>
<td><font size=1 face="sans-serif">07/31/2013 11:16 AM</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Subject:</font>
<td><font size=1 face="sans-serif">Re: [RE-wrenches] Outback AC coupling
Sunpower?</font>
<tr valign=top>
<td><font size=1 color=#5f5f5f face="sans-serif">Sent by:</font>
<td><font size=1 face="sans-serif">re-wrenches-bounces@lists.re-wrenches.org</font></table>
<br>
<hr noshade>
<br>
<br>
<br><font size=3>Ray<br>
You did not mention the XW, it frequency dithers so it is a pretty straight
forward setup. It also comes in 4, 4.5 and 6KW<br>
<br>
Ryan<br>
</font><img src=cid:_2_0FF159C80FF15650006CA59D88257BB9><font size=3><br>
</font>
<br><font size=3>On 7/31/2013 2:04 PM, Ray Walters wrote:</font>
<br><font size=3>Hi Kelly;<br>
<br>
I agree the Radian system is appealing. Its basically uses a circuit
breaker that can be controlled like a relay as well, and just disconnects
the GT inverter.<br>
I'm going to offer a brief table of what I've found for my choices:<br>
</font>
<table border width=100%>
<tr valign=top>
<td width=9%><font size=3>Brand</font>
<td width=24%><font size=3>Control Method</font>
<td width=27%><font size=3>Pros </font>
<td width=38%><font size=3>Cons</font>
<tr valign=top>
<td><font size=3>SMA Sunny Island</font>
<td><font size=3>Frequency shift to disconnect GT inverter</font>
<td><font size=3>simplest wiring, Trusted GT industry player</font>
<td><font size=3>most expensive, Freq shift can cause other problems</font>
<tr valign=top>
<td><font size=3>Outback Radian</font>
<td><font size=3>Remote controlled Circuit breaker disconnects GT inverter</font>
<td><font size=3>fairly simple wiring, relay and breaker are combined,
better control of battery charging</font>
<td><font size=3>still expensive, not available in smaller than 8 kw model</font>
<tr valign=top>
<td><font size=3>Magnum</font>
<td><font size=3>Diversion load controls for battery regulation (soon
to offer AC load control)</font>
<td><font size=3>lower cost, proven technology, freq shift control offered
as fail safe</font>
<td><font size=3>most complicated wiring, diversion loads not always
reliable or available</font>
<tr valign=top>
<td><font size=3>Modsine Backup system</font>
<td><font size=3>no AC coupling, just an old fashioned backup system</font>
<td><font size=3>low cost</font>
<td><font size=3>complicated, needs customer interaction, not as efficient,
GT PV not used, dedicated PV modules only charge backup system</font>
<tr valign=top>
<td><font size=3>Generator</font>
<td><font size=3>No AC coupling, generator runs backup loads</font>
<td><font size=3>lowest cost, backup power available for as long
as outage (no batteries)<br>
best for week long outages that only occur every few years</font>
<td><font size=3>Not Renewable, fuel storage issues, doesn't switch fast
enough to maintain computers, etc.</font></table>
<br><font size=3><br>
<br>
I'm still pricing out the options, but the SI and Radian seem a bit overkill
for smaller systems. Backup inverter power of just a couple thousand
watts is all that most people need. The Magnum is appealing, but
I have quite a bit of experience with load diversion controls from wind
and Hydro systems, and I really feel that its overly complicated for the
less than 1% of the time that the grid is out. Keeping the battery
from being damaged is what's important, but maintaining full 3 stage charging
for a couple of days a year is not. The batteries can be properly
charged once the grid returns. May be able to use Outback's ROCB
with the Magnum? That might get the best of both worlds.<br>
If I was building the entire system to start, I'd just use a single Outback
GVFX with its own PV array, and add GT inverters and array that were independent
for the rest of the GT requirements. This project however is retrofitting
an existing GT system. <br>
I've done many backup systems in the days before Grid Tie, and they work
fairly well. Basically either the modules are not used much of the
time, or the customer has a few circuits that are on the backup system
(off grid) all the time. They operate it just like an off grid system,
the only difference is that when its time to run a generator, they can
just switch to the grid. These are not for your average customer,
but can work well for someone that likes to save money and tinker.<br>
Another consideration is that if the battery bank is large enough relative
to the array, over charging becomes less of an issue; especially with flooded
cells that can stand a bit of over charging ("equalization")
every now and then. However, I can see that the average small sealed
battery bank hooked up to several KWs of PV could get ruined in a day.<br>
I'll close with a quote from Joe Swartz in his 2012 Solar pro magazine
article : <br>
<br>
"AC coupling is still the Wild West of renewable energy applications"<br>
</font>
<br><tt><font size=3>R.Ray Walters<br>
CTO, Solarray, Inc<br>
Nabcep Certified PV Installer, <br>
Licensed Master Electrician<br>
Solar Design Engineer<br>
303 505-8760</font></tt>
<br><font size=3>On 7/30/2013 11:37 PM, Kelly Keilwitz, Whidbey Sun &
Wind wrote:</font>
<br><font size=3>Ray, </font>
<br><font size=3>The battery-based inverter in an AC-coupled system should
not be grid-interactive. The grid passes through the BB inverter to the
grid-direct inverter(s). The BB inverter is there to create a stable grid-like
signal for the grid-direct inverters when the grid is not present, and
to manage the batteries. Thus, the pass-through AC capability of the BB
inverters normally (there is a complicated work-around) must be able to
handle all of the PV AC output, when loads are low.</font>
<br><font size=3>You probably are aware, but to make it clear in this thread:
the system needs to have some method to protect the batteries from overcharging,
as a result of the grid-direct inverter output when the grid is down and
loads can't use all the solar energy available. With the Sunny Islands
it's done by a signal that reduces output from the Sunny Boys without disconnecting
them. With Outback and others it's done with a installer-designed relay
that disconnects the grid-direct inverter when the battery voltage gets
to a set point. We haven't done an AC-coupled system with the Radian, yet.
Sounds like the remote controlled breaker is Outback's approved and listed
way to do it. About time.</font>
<br>
<br><font size=3>-Kelly </font>
<br><font size=2><br>
Kelly Keilwitz, P.E. <br>
Principal<br>
Whidbey Sun & Wind<br>
Renewable Energy Systems<br>
NABCEP PV Installation Professional<br>
WA Electrical Administrator</font><font size=2 color=blue><u><br>
</u></font><a href=mailto:kelly@whidbeysunwind.com><font size=2 color=blue><u>kelly@whidbeysunwind.com</u></font></a><font size=2><br>
PH & FAX: 360.678.7131</font><font size=3><br>
<br>
</font>
<br>
<br><font size=3>On Jul 30, 2013, at 4:23 PM, Ray Walters <</font><a href=mailto:ray@solarray.com><font size=3 color=blue><u>ray@solarray.com</u></font></a><font size=3>>
wrote:</font>
<br>
<br><font size=3>The Outback rep got me some good info, and I'm liking
the Radian with the Remote controlled breaker to control the GT inverter
when the grid is out. I've heard of quite a few problems related
to the Sunny Island frequency controlled system.<br>
My question is can off grid inverters like the Magnum be AC coupled? I'm
trying to get the price down, and still handle the 240 vac input from the
GT inverter.<br>
I penciled out the Radian and I was topping $10k before installation.
This customer is hoping for a solution under $10k, and closer to $5k if
possible. I think an elegant lower cost solution for Grid tie with
battery back up is in order. A Radian Lite?<br>
For backup, it could even be mod sine, as it wouldn't be much worse than
generator power or the average UPS setup.<br>
<br>
<br>
R.Ray Walters<br>
CTO, Solarray, Inc<br>
Nabcep Certified PV Installer,<br>
Licensed Master Electrician<br>
Solar Design Engineer<br>
303 505-8760<br>
<br>
On 7/30/2013 2:59 PM, Ray Walters wrote:</font>
<br><font size=3>Hi All;<br>
<br>
I know AC coupled systems have been covered before, but I have a new issue:
positive grounding. A customer with an existing 8kw Sunpower
system wants to add backup. He was put off by the high cost the
Sunny Island, so I was steering him towards a single Outback VFX coupled
to just one of his 3 inverters. The issue is how will the VFX work
with positive grounded inverters. I'm assuming that since the two
inverters will only be connected by AC, that the positive vs negative grounding
of their separate DC systems will not matter. Any experience with
this particular scenario: Sunpower system AC coupled to an Outback?<br>
Also, would I even need a GVFX, since the inverter would only be used during
outages (which might allow a generator to be used later as well)
A VFX should still AC couple to the GT inverter during an outage,
right?<br>
<br>
Thanks as always,<br>
</font>
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