[RE-wrenches] More on AC coupling

Matt Tritt solarone at charter.net
Wed Nov 26 16:40:46 PST 2008


UB right, Tump. These things aren't exactly something you will ever find 
at Home Depot! BUT, and it's a big one, if you count all the %$!#& time 
and energy usually required to design, fabricate and re-design a really 
good off grid system, the extra money might just be woth it. ;-)

Matt T

Tump 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?
>>               o For now I have them set at: 1^st load to kick on at
>>                 float voltages, 2^nd to kick on at bulk voltages and
>>                 3^rd 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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