[RE-wrenches] Off Grid Optimizers

[Ray]

We've discussed AC coupled many times.   Aside from the issues Michael 
brought up, I need to remind that not having at least some DC  PV 
charging means that when the AC system shuts down for any reason, so 
does all the PV charging.  If Li+ batteries get discharged to their low 
voltage shut off:  Dark Starts anyone? With lead acid, DC coupled PV is 
just as critical to keep the battery from sulfating.

Which would you want?

Scenario 1:Come back to trouble shoot a system shutdown,  try to reboot, 
only to find no battery voltage to even test with. or

Scenario 2:  You will have a battery that is being charged, if not 
already at full charge.

For GTB?, you decide how important this issue is,  but for Off grid you 
are putting your customer in serious jeopardy without power. Unless they 
have a manual bypass, the generator won't pass through to the loads, or 
charge the battery either.  This is not theory, We've had to fix these, 
and in some cases replace the battery bank that was damaged after 
sitting dead too long.

My previous post in favor of AC coupling was only as a supplement to a 
solid DC PV system, or for module level optimization in partial shade 
conditions.

Ray Walters
Remote Solar
303 505-8760

On 11/1/19 1:08 PM, Michael Morningstar wrote:
> You know Murphy? That is Murphy of Murphy’s Law?  He’s gotta just love 
> the idea of AC coupled off-grid systems. The OB, SB, Li system Jay 
> described is going to keep him (Murphy) and the installer very busy at 
> some point. The further away the system is from civilization, the 
> higher the odds of chicanery and headaches. Systems that need backup 
> safety controls seem inherently risky too.
>
>
>
>> On Oct 31, 2019, at 11:06 AM, jay <jay.peltz at gmail.com 
>> <mailto:jay.peltz at gmail.com>> wrote:
>>
>> HI Drake,
>>
>> I was just talking with a colleague the other day about a project he 
>> did.
>> New Radian, AC coupling, lithium batteries, SB inverters.  Everything 
>> is working just as it should with the GT inverters tapering during AC 
>> coupling frequency shift mode.
>>
>>
>> I would say you are fine, and while I can’t say for sure if the 
>> Enphase will work that way, they should as they are all designed to 
>> the same parameters rule 21.
>>
>> I always do recommend a aux relay for backup/shutoff  should there be 
>> some kind of issue.
>>
>> With the Envoy you’ll be able to see that tapering as well.
>>
>> Seems like a good option for your application
>>
>> jay
>>
>>
>>
>>
>>
>>> On Oct 31, 2019, at 9:49 AM, Drake 
>>> <drake.chamberlin at redwoodalliance.org 
>>> <mailto:drake.chamberlin at redwoodalliance.org>> wrote:
>>>
>>> Hi Jay,
>>>
>>> Between 2160 and 2880 Watts of added array. We will be using a new 
>>> Radian.
>>>
>>> Drake
>>>
>>> At 11:49 AM 10/31/2019, you wrote:
>>>> How many watts are you adding as ac coupling?
>>>> And presuming its an older 8k radian?
>>>>
>>>>
>>>> Jay
>>>>
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>
> *
>
> *
>
> *Michael **Morningstar*
> *
> *
> */Morningstar Electric/*
> PO Box 1494
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