[RE-wrenches] Solaredge AC-coupling revisited

[Kirk Herander]

John,

 

The time has come where I am about to install the Solaredge system w/
AC-coupling capability. The actual battery inverter & batteries will come
later as an add-on. Is the Sunny Island the only battery inverter that uses
the frequency shift algorithm? The Solaredge software allows the Sunny
Island to control it, backing off AC charging off like the Sunnyboy,
correct? How do I know the inverter I'm getting has the new firmware
installed? Thanks. Anyway I would be interested in your white paper on the
subject if it's available.

Although I have AC-coupled before I feel more and more uncomfortable using a
relay as an on/off charge controller, especially on large arrays vs.
relatively small battery banks. Aside from the stone-age regulation akin to
a Trace C-30, if the relay were to fail the battery bank could seriously fry
in a matter of minutes.

 

Kirk Herander

VT Solar, LLC

dba Vermont Solar Engineering

NABCEPTM Certified Inaugural Certificant

NYSERDA-eligible Installer

VT RE Incentive Program Partner

802.863.1202

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of John Berdner
Sent: Wednesday, December 19, 2012 1:35 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Solaredge AC-coupling

 

Kirk:

 

We have a new version of firmware (in production January 1, 2013) that
supports frequency shift power control, e.g. Sunny Island.

I am preparing a white paper on how to set it up but can walk you through it
or we can preprogram it for you here and drop ship it to you for your
distributor.

All of our recent product has an SD card slot so you can upgrade firmware in
the field to the latest version should you receive an inverter with older
firmware.

Feel free to contact me offline to discuss details on how to program.

 

We do not support ac coupling to other battery inverters that do not use a
frequency shift algorithm.

There are a couple of issues with AC coupling to inverters that just use a
relay to disconnect the grid tied inverter with a relay (ours our anyone
else's).

 

1)      Every time you open the relay you create a grid fault and the
isolation relays in the grid tied inverter cycle. Cycling on an off every 5
minutes is really hard on the relays and can lead to premature failure.

2)      The result of this relay cycling is that you end up with on/off
charge control which is not very effective.  On/Off charge means the battery
can never become fully charged (negative offset from the target set point).
If you increase the set point then you increase gassing which results in
higher maintenance for flooded batteries and possible damage for sealed
batteries.  It is a no win situation.

 

The magnitude or these downsides also depends on the intended application.
For a true off grid application I would never recommend AC coupling unless a
frequency shift algorithm is used.  An off grid system has the potential to
spends a lot of time in "regulation" and, because of the on/off charge
control, the batteries never really get charged - which is not good for
performance or longevity.  In a grid backup application these downsides are
less of an issue because the grid is rarely down and when it is down the
battery is normally discharging so the system is unlikely to spend much time
in "regulation".  In my experience folks that have grid backup systems do
not have the same energy awareness as those that live off grid and so they
use more power.

 

Best Regards,

 

John Berdner

General Manager, North America

 

Description: SmallBannerPictEngnew

 

3347 Gateway Boulevard, Fremont CA 94538 USA  (*Please note of our new
address.)
T: 510.498.3201 ext 747

M: 530.277.4894 

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kirk
Herander
Sent: Tuesday, December 18, 2012 1:16 PM
To: RE-wrenches
Subject: [RE-wrenches] Solaredge AC-coupling

 

Hello,

 

Anyone out successfully AC-coupled a Solaredge inverter with an Outback or
other battery-based inverter? Thanks. I may want to do it for an upcoming
job.

 

Kirk Herander

VT Solar, LLC

dba Vermont Solar Engineering

NABCEPTM Certified Inaugural Certificant

NYSERDA-eligible Installer

VT RE Incentive Program Partner

802.863.1202

 

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