[RE-wrenches] More on AC coupling - SI and SB

Wed Nov 26 08:57:45 PST 2008

Hi Geoff,

Nice heads up on the SI needing to be “set up” prior to commissioning.

We are getting closer to a similar design ourselves. We have a SB7000US being fed by 36 Sanyo Hit Power 200’s on the drawing board that we are going to feed into a grid tie inverter system. Right now I am convinced that the SI5048’s will need to be paired up in order to feed this amount of current back through them to the grid if there aren’t any loads on in the residence, unless someone can let me know that this is not the case. 

I envision each SI requiring its own manual transfer switch between it and the grid, feeding the dedicated loads AC subpanel in case we need to pull it off the wall for servicing. Is this typical in your designs? Rethinking this if one SI is down for repairs the entire AC sub panel will need to be fed by the grid so there is a balanced 240VAC signal to it.

We are looking into the new East Penn Deka Unigy ll sealed batteries. They seem to be a good deal less money than the GNB’s.  Anyone have any experience with these? 

With two SI5048’s sucking on this battery bank there is the possibility of some serious current transfer taking place. We are proposing an absolute minimum battery size that can go full load draw down for three hours, to 50% DOD, my inclination is to make this 6 hours. At 3 hours we would need a 500 amp hour battery. What are others doing about battery sizing in this scenario? (our client hasn’t revealed what loads he wants to back up unfortunately so we are approaching this in this manner)

Right now we are still in the dark as to whether or not there will be a gen set involved. 

I do know a WebBox will be interfaced between the SI’s and the SB’s.

Thanks for the continuing discussion on this thread and Happy Thanksgiving to one and all.

Sincerely,

Chris Worcester
NABCEP Certified PV Installer
Phone: 530-582-4503
Fax: 530-582-4603
www.solarwindworks.com <http://www.solarwindworks.com/> 
chris at solarwindworks.com
"Proven Energy Solutions"

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Geoff Greenfield
Sent: Wednesday, November 26, 2008 7:28 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] More on AC coupling - SI and SB

Matt-

What is your prefered/recomended way to address the 240 VAC SB series (we typically dont want to use a bunch of 700s or 1800s) and the 120 VAC SI series?  We used a pair of Outback PSX-240s but that was extra work/cost.  Other (larger) transformers? Torroid coil? Eaton? I'm surprised SMA doesnt have a nice interface worked out for the North American market...

Also wrenches... if you go down this route, invest the time ahead of time on learning/preping for the set up etc for SI in this application.  It is not out of the box ready to go, but involves a software upgrade, laptops and the right patch cord (an issue if you are 5 hours away...).

For a brighter energy future,

Geoff Greenfield
Founder and CEO
Third Sun Solar & Wind Power Ltd.
340 West State Street, Unit 25
Athens, OH 45701

740.597.3111     Fax 740.597.1548
www.Third-Sun.com

Clean Energy - Expertly Installed

----- "Tump" <tump at hughes.net> wrote: 
> 

Matt, I have long been interested in installing the SMA SI & SBs but I have a VERY tough time selling $9ks worth of inverters, just to get things started.

In the system below I would not of hesitated in installing the SMA SI & SB! I too agree that w/this type of scenario described below, I  would have given quite a bit of thought to using the SMAs. Can't beat the battery charging, no charge controllers & expandability.

 Please if there is someone out there that has had experience w/ the SMA SI & SB let us know if it is all that it is cracked up to be!

With passport in hand, I offer my help if someone out there  has a large system like this, that will be using the SI & SB/WB  type of set up.

TUMP

> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Matt Tritt
> Sent: Tuesday, November 25, 2008 9:21 PM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] More on AC coupling
> 

I am curious as to why OutBacks were used for this system instead of using SunnyIslands and SunnyBoys? From what I can tell about the SI system, virtually no aspect of battery charging, auto gen-start/stop, and interactive inverter control has been overlooked - or remains to be engineered in the field by the installer. Because SunnyIslands have the ability to "talk" to Sunny (or Windy)Boys, excess energy is taken care of by "integrated load shedding" - no need for multiple relays, dumpoads and voltage sensors. :-) The only limitation to these systems (and only in 60 Hz land) is a maximum of 20 kW single, and 15 kW three phase per autonomous load. I really like the flexibility of being able to connect all AC inputs on the same line, as well as having the option to do direct battery charging from a DC source (as long as you use a shunt to measure current).
> I know this doesn't answer your questions, but for similar applications in the future it would be good to take a close look at the SunnyIsland system. They're cool.
> Matt T
> Mark Dickson wrote: 

> 

Hello Wrenches,

On the heels of the previous thread:

We just got finished installing a system that utilizes an Outback Quad stack and a 5.2kW array coupled to the AC panel via a Fronius IG5100--due to a long home-run.  The VFX’s are wired into the home in their traditional manner, providing the “grid” for the Fronius.  As the solar comes in, excess power not used in the home back feeds the batteries through the VFX’s.  I have a series of relays operating dump loads and finally a power cut-off for when the batteries reach critical level.  We installed the system yesterday and turned it on for a test run (then back off to power it up in 2009 for the ITC’s)—it worked great!

I have a couple questions for you all:

*	Seems how we are back feeding the inverters and forfeiting their charge control, where would you set the dump loads to kick on? 

*	For now I have them set at: 1st load to kick on at float voltages, 2nd to kick on at bulk voltages and 3rd to kick the solar power off at the EQ voltages.  Does this make sense?  The bank is made up of Rolls 4ks-25ps batteries. 

*	Following a recent discussion on the Wrenches list with a similar system:  Do I need to worry about back feeding the generator if it is runnin in the morning when the sun comes up?  Do I need a relay that will shut it down when solar comes on line? 
*	I plan on setting the Absorb and Float set times to a miimum.  Would you recommend this? 

Thanks for your input!

Mark Dickson

Oasis Montana Inc.

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