outback-generator-on grid [RE-wrenches]

Matt Tritt solarone at charter.net
Fri Apr 6 10:35:27 PDT 2007


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OK, Sunny Island. The new US version will accomplish what you want to 
do, but you will need a grid-tied inverter on the output of the PV to 
feed the input buss of the SI.

Matt T

Eric Youngren wrote:

>Somebody correct me if I am wrong but it seems to me that the underlying
>problem here is that we have good battery based (voltage source) inverters
>and good grid-tied (current source) inverters but it is difficult to do both
>jobs effectively with a single unit.  Yes the GTFX is capable of it but the
>problem with generators, limit of 2 in a stack and the lower conversion
>efficiency for grid-tie makes it a problematic choice.
>
>I am designing a good sized GT w/batt system right now and I am leaning
>towards an AC coupling approach using two different inverter types to
>accomplish the different goals (grid-tie and battery back-up).  I have not
>done this yet, however, so I am hoping to throw it out for discussion and
>advice from those that have been there.
>
>My thinking right now is to use a quad stack of FX3048 on a ~1600 AH
>industrial battery and approx 8 kW of PV on two Sunny Boy 3800s.   The Sunny
>Boys will be wired into backfed breakers in a 200A panel that will be fed by
>the Outback stack.   During normal operation the Sunny Boys will synch with
>the grid and pass current through the Outback stack and out through the
>utility meter.  When the grid fails the Outbacks will take the load and use
>any surplus incoming AC from the Sunny Boys to charge the batteries.  The
>existing 15kW diesel standby generator will be there on its currently
>installed auto transfer switch to feed the main panel and the chargers in
>the Outbacks when battery voltage drops. I know that I'll need a diversion
>controller and dump load to prevent overcharging by the unregulated charging
>from the Sunny Boys.  Is there anything else I should be thinking of?
>
>It seems to me that this could be a relatively elegant, efficient and robust
>way to accomplish multiple goals. (The Sunny Island is another option that
>may be a bit more elegant, but I do like those Outback inverters.) There is
>also a long distance wire run between the array location and the battery
>room which makes this arrangement appealing.  
>
>Am I correct in my thinking that it will be more effective and efficient to
>use a grid-tied inverter for selling PV power to the grid and a battery
>based inverter to back up loads and keep the batteries charged? Will they
>play together well?  Or can both of these jobs be done effectively with a
>single machine, like the GTFX?  Or is the GTFX a product that the market
>wants but basic inverter topology makes difficult to accomplish?  Or is it
>the UL listing required tolerances for grid-backfeed that make it difficult?
>
>Thanks,
>
>Eric Youngren
>Rainshadow Solar
>Orcas, WA 
>
>
>-----Original Message-----
>From: Todd Cory, Mt. Shasta Energy Services
>[mailto:toddcory at finestplanet.com] 
>Sent: Thursday, April 05, 2007 5:58 AM
>To: RE-wrenches at topica.com
>Subject: Re: outback-generator-on grid [RE-wrenches]
>
>
>IF you get the Outback to accept the power from an inverter generator, 
>you will still need an external transfer switch to change the AC input 
>to the inverter from grid to gen and someone (the customer) to manually 
>(using the mate) change the AC input from grid to gen.
>
>An AC battery charger plugged into the generator will not produce much 
>current due to the lower peak to peak power output of most traditional 
>generators. There is also the possibility of selling the generator 
>output (via battery charger) to the grid if you continue to leave it 
>running after the grid has been restored.
>
>To my knowledge, there is no elegant way out of this as of yet.
>
>Todd
>
>Brad Bassett wrote:
>
>  
>
>>If one of the inverter generators doesn't do it for you, it's easiest to 
>>just use a separate AC battery charger plugged into the generator (or 
>>two of them if they are 120v and the gen is 240v). A lot easier than 
>>most DC generators, except maybe one of those small auto generator 
>>setups. 
>>
>>Brad Basset
>>   
>>
>>    
>>
>
>
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