[RE-wrenches] Grid-Tied, PV by AC or DC

Sun Mar 4 08:12:56 PST 2012

Jay,

We have installed a number of AC Coupled systems using Sunny Boys and Sunny Islands.  One important consideration in this approach is to connect the inverters (Sunny Boys and Sunny Islands) together with a communication cable and Communication Cards and to upload new software into the Sunny Boys that let them know when the grid is down to operate in off grid mode. In this way when the grid is down the Sunny islands can limit the output of the Sunny Boys to meet the demand of the loads in the protected loads sub panel. Without the communication between the inverters, if the grid is down and the output of the Sunny Boys exceeds the demand of the loads in the protected load sub panel, then the Sunny Island will phase shift and the Sunny Boys will completely disconnect and then wait five minutes to try and connect again and will continue to do this until the output of the Sunny Boys does not exceed the demand of the loads.   So it is all or nothing without  communication between the inverters.  This would seem to hold true as well for Sunny Islands mixed with any other Grid Tied inverters that are not of the SMA family and can not effectively talk to each other.

Larry

Larry Brown
Sun Mountain
NABCEP Certified PV Installer

On Mar 4, 2012, at 10:25 AM, jay peltz wrote:

> HI Darryl,
> 
> Is this a UL listed application for the Radian/Outback?
> 
> And in following this thread about AC coupled:
> Given the higher efficiency of the batteryless inverter and fantastic MPP, vs the relatively high losses with the 600v xantrex or standard CC/inverter losses, I would use the AC couple technique.
> 
> Jay
> 
> peltz power
> 
> 
> On Mar 3, 2012, at 8:06 AM, Darryl Thayer wrote:
> 
>> A few years back I made some year long measurements on an outback GVFX and a sunny boy for net energy to the grid I got only a few percentages not 10%  I think one of the problems is the battery selection, these new batteries from Outback seem to have very low self discharge so very little energy should be expended to keep them charged.  I am trying to close on a system where the distance from the solar array to the house is far, so I am planning to AC couple to a Radian to the grid, and I have been sucessful with AC coupleing on GVFXs and Outback assures me it will workas well with theRradian.  This install is very sensitive to LOL (loss of load) and has the generator ready to go, but for the short outages that he has it is a hassel.  (he has worn out one generator all ready, it was a construction grade genny) 
>>  
>> I am hoping if this system is a go to consider a Xantrex 600 volt charge controller, but it depends upon the customer
>> thanks for the patence
>> Darryl
>> 
>> From: Drake <drake.chamberlin at redwoodalliance.org>
>> To: RE-wrenches <re-wrenches at lists.re-wrenches.org> 
>> Sent: Friday, March 2, 2012 9:31 AM
>> Subject: Re: [RE-wrenches] Grid-Tied, PV by AC or DC
>> 
>> I think the AC coupled approach would be the best.  For the 10KW system, a pair of Sunny Islands fed by Sunny Boys would make an efficient system.  Since there is no generator, the system should be fairly straight forward. 
>> 
>> At 02:06 AM 3/2/2012, you wrote:
>> 
>>> i think mark was asking more about ac coupling to get away from the horrible inefficiencies of battery based, grid-tied inverters.
>>> 
>>>  
>>> 
>>> as an experiment, i have been thinking about ac coupling one (or more) of my arrays on my outback system to gain 10% over having the gvfx do the selling.
>>> 
>>>  
>>> 
>>> stc to ptc usually costs about 20%, then losing another 10% in the inverter is a real performance hit. i advise customers about phantom loads and conservation, when actually the battery based inverter is itself the big lump under the carpet!
>>> 
>>>  
>>> 
>>> todd
>>> 
>>>  
>>> 
>>>  
>>> 
>>>  
>>> 
>>>  
>>> 
>>>  
>>> 
>>> On Thursday, March 1, 2012 7:07pm, "Maverick Brown [Maverick Solar]" <maverick at mavericksolar.com> said:
>>> 
>>> My two cents:
>>> "battery-based inverter w/ PV on the DC side via charge controllers"
>>> Simply replace the GT inverter with a Xantrex 600V Charge Controller plus the 48V Grid Interactive Inverter of your choice and added battery bank, etc.
>>> Until the market is saturated with unneeded GT Inverters, you will be ok. ;-)
>>> Try your best to provide enough battery for at least 24 hours of outage at 50% DOD. You may have add a Sub-Panel or Manual Transfer Switch.
>>> Thanks
>>> Maverick
>>> Maverick Brown
>>> BSEET, NABCEP Certified Solar PV Installer Â® # 091209-26
>>> President & CEO
>>> Maverick Solar Enterprises, Inc.
>>> Billing:  PO BOX 1229, Dripping Springs, TX 78620
>>> Office:       512-919-4493
>>> Fax:           512-607-6398
>>> Cell:          512-460-9825
>>> Corporate: http://www.mavericksolarenterprises.com/
>>> 
>>> From: re-wrenches-bounces at lists.re-wrenches.org [ mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of toddcory at finestplanet.com
>>> Sent: Thursday, March 01, 2012 5:46 PM
>>> To: RE-wrenches
>>> Cc: 'RE-wrenches'
>>> Subject: Re: [RE-wrenches] Grid-Tied, PV by AC or DC
>>> 
>>> excellent question mark... and one which has been on my mind as well, being most of my work is bbgt.
>>> 
>>>  
>>> 
>>> todd
>>> 
>>>  
>>> 
>>>  
>>> 
>>>  
>>> 
>>> On Thursday, March 1, 2012 11:37am, "Mark Frye" <markf at berkeleysolar.com> said:
>>> 
>>> Folks,
>>> 
>>> I have a residential grid-tied customer in a net metered utility with a favorable TOU rate.
>>> 
>>> They could use about 10 kW of PV to offset 100% of their usage.
>>> 
>>> But, they also complain about regular power outages in their neigborhood. They don't want a generator.
>>> 
>>> With reliable AC coupling now available, do we yet know which is the more advantagous architecture; grid-tied, battery-based inverter w/ PV on the DC side via charge controllers, or grid-tied, battery-based inverter w/ PV AC coupled via grid-tied, utility-based inverter?
>>> 
>>> Your thoughts? 
>>> 
>>> Mark Frye 
>>> Berkeley Solar Electric Systems 
>>> 303 Redbud Way 
>>> Nevada City,  CA 95959 
>>> (530) 401-8024 
>>> www.berkeleysolar.com 
>>> 
>>> 
>>> 
>>> Sent from Finest Planet WebMail.
>>> 
>>> 
>>> 
>>> Sent from Finest Planet WebMail.
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>> Drake Chamberlin          
>> ATHENS ELECTRIC LLC
>> OH License 44810         
>> CO license 3773
>> NABCEP Certified PV
>> 
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