Adding separate DC coupled storage in addition to existing Micro-array.

[jcondemn]

In 2018 I installed 3kw of solar on my house. 12 X 290 watt panels, 12 IQ7 micros, back-fed breaker. It is a very simple system and I really enjoyed the design (simple) and install. This array is on a 10-year production incentive from my utility provider as well.

With current prices I would like to add 11 more panels to my system. Since the current array is on a production incentive contract with it's own dedicated production meter, I will be adding a separate system. I was thinking of adding a DC coupled battery storage with a critical loads panel.

If I went with an Outback Skybox hybrid inverter, LG chem battery and 11 (350w) panels. How would this system interact with the existing micro-inverter array I already have installed? Do I need to do anything special?

Thanks Jim,

House_Solar.JPGHouseLineDrawing.JPG

[Ampster]

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If I went with an Outback Skybox hybrid inverter, LG chem battery and 11 (350w) panels. How would this system interact with the existing micro-inverter array I already have installed? Do I need to do anything special?
.........

You have two basic options only one needs to interact with an Outback Skybox. I will try to describe the high level functionality of each and then you can describe your goals in more detail.

One option would be to just install the Skybox with a critical loads panel and have it support your critical loads and be available for backup in the event of power outages. Within that option, if your power company allows additional export , you could configure the Skybox for export. In either of these scenarios if the grid went down only the solar attached to the Skybox would operate. The GT micros and the Skybox would be independant of each other.
The second option would be if you want the additional production from your existing GT solar to run during power outages then you would want to AC couple the GT inverter to the Skybox. I can go into more specifics if that is your goal. Again the question of how much additional power you provider will allow to be exported may determine how the system is configured. I have a limit of 1kW additional power when I installed my Skybox so I set the export limit to the original permission plus 1kW allowed. The Skybox is flexible in that regard. The only thing special you would need to do with the existing system to get the benefits of AC coupling is to rewire your existing GT micros circuit to your critical loads panel. There are lots of details I can go into if you are familiar with electrical codes, otherwise that is the concept and you can leave the details to your installer or electrician.
The picture does not look like California so details of your power company requirements would help inform the conversation along with your goals.

[jcondemn]

Thanks for the response!!

I am in Minnesota and my power company is Xcel Energy. Not sure on the allowable export, I will have to do some more research. As far as my overall goals for the system:

• Maximize available roof space with more solar.
• Critical loads backup in case of power failure (refrigerator and lights are most important).
• Utilize TOU rate structure for cost savings (lowest priority).

Option #1,
I think I understand Option #1, please see the attached diagram.
Skybox.jpg

Option #2,
What would the setup look like for AC coupling the existing GT system to the SkyBox?
Skybox2.jpg

[Ampster]

Yes, that is what they would look like.

[jcondemn]

I see a definite advantage to option 2 since in the event of a power outage, the local grid would have the energy from the batteries plus both solar arrays. I would like to go with that option.

Any disadvantage or something I am overlooking? Seems pretty straightforward, adding a sub panel, switching the existing GT array to the sub panel.

[Ampster]

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Any disadvantage or something I am overlooking? Seems pretty straightforward, adding a sub panel, switching the existing GT array to the sub panel.

The sizing of bus bar of the sub panel is subject to a NEC rule that you need to plan for when you pull your permits or source the parts. Consult your local code for any other requirements. There are some good resources on the Outbackpower website and user forum regarding which modes to use based on your goals and size of batteries.

If you want to maximize self consumption you may want to purchase external CTs (current tranformers) so you can cover all your consumption before selling to the grid. More on that later if interested. There is a good thread on that subject on the Outbackpower user forum. The Skybox is very flexible.

It is important to understand the details of your current agreement with Xcel Energy to see if it is feasible to expand your capacity to export. Increasing export can be the optimum way to take advantage of Net Metering. You can still use batteries for backup and load shifting in that case. If no expansion is permitted by Excel, I am of the opinion that you can add capacity behind the meter without exporting. You most likely will need a building permit. That is what I have done. The regulations may vary by state, county or city so research is necessary and double check assumptions, especially ones made on advice from anonymous sources like me on the Internet.