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Solar power direct to home?
Posted by: anonymouse1
Date: August 09, 2022 11:21PM
A buddy installed a massive array of solar power. He doesn't have any batteries; just sells to the grid and get credits to use when it's dark.

Is there any way to have some kind of interlock to send the power directly to his house if/when the grid goes down?

Thanks!
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Re: Solar power direct to home?
Posted by: testcase
Date: August 10, 2022 12:06AM
I'd be VERY surprised if there wasn't a way to do that.
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Re: Solar power direct to home?
Posted by: davester
Date: August 10, 2022 12:11AM
The only way to do it is with a battery bank and charge controllers/inverters. It's extremely expensive, so much so that a battery backup system typically rivals the cost of a grid-tied solar system, thus doubling your cost.



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Re: Solar power direct to home?
Posted by: TheTominator
Date: August 10, 2022 07:04AM
Quote
davester
The only way to do it is with a battery bank and charge controllers/inverters. It's extremely expensive, so much so that a battery backup system typically rivals the cost of a grid-tied solar system, thus doubling your cost.

agree smiley


Quote
anonymouse1
Is there any way to have some kind of interlock to send the power directly to his house if/when the grid goes down?

No, not really. His grid-tie system does not provide the type of power that can be used directly.
But it can be done by spending a lot more money.

The solar industry calls this capability a "hybrid solar" system.
When you install solar panels, you generally have a choice of two designs: "grid-tie" or "off-grid battery".

The "grid-tie" systems are engineered to feed all of the power to the power company. There is no provision for powering the house. All of the components and wiring are optimized for this task. There is no usable energy storage and the grid-synchronized 60Hz AC power generated has unregulated voltage (using grid-tie inverters). The dirty power is pushed to the grid trusting that larger pool of regulated power will not be affected by the over or under voltage of this small source. (That may change as more grid-tie systems are added to feed the grid.). This type of grid-tie inverter is designed to require an active power grid and will not provide power when the grid is down. There may be many small grid-tie inverters installed each connected to an independent string of solar panels so that some may be shaded or face a different direction and not bring down the others.

The "off-grid" system is engineered to store power in an on-site battery bank. The solar wiring and components are optimized to feed the battery design. The DC battery bank would then power an Inverter to provide AC power to the site. This big and centralized inverter must provide stable and regulated power with enough capacity (and surge capability) to power the site's needs. The battery and the inverter are very large costs and are specific to the off-grid design. This type of inverter must never feed power to the grid (both legally and for safety reasons).

The hybrid systems combine elements of both systems but largely have only the solar panels in common. Even that is a compromise since usually the solar panels are set up differently and are often of different construction in the two types of systems. Hybrid systems are very expensive since you are essentially buying both a grid-tie and an off-grid system.



Edited 1 time(s). Last edit at 08/10/2022 07:09AM by TheTominator.
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Re: Solar power direct to home?
Posted by: mrbigstuff
Date: August 10, 2022 08:31AM
Also, battery back up systems have not been approved in many localities, so the permitting required is a real fuster cluck.
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Re: Solar power direct to home?
Posted by: kj
Date: August 10, 2022 01:37PM
I just wish I could charge my EV with solar, but it's a lot more complicated than I would have thought.
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Re: Solar power direct to home?
Posted by: Article Accelerator
Date: August 10, 2022 02:52PM
Quote
anonymouse1
Is there any way to have some kind of interlock to send the power directly to his house if/when the grid goes down?

Yes, you would need a "Black Start Capable" system:

[basc.pnnl.gov]
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Re: Solar power direct to home?
Posted by: btfc
Date: August 10, 2022 06:28PM
Battery options abound:


[www.amazon.com]


[solarmetric.com]
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Re: Solar power direct to home?
Posted by: GGD
Date: August 10, 2022 07:34PM
Quote
btfc
[solarmetric.com]

Interesting table from that article, and their conclusions about "expensive".

Quote

Pricing Showdown (Excluding Professional Installation Costs)

Tesla Powerwall – $7,500 for 13.5kwh
LG Chem RESU – $5,900 for 9.8kwh
Sonnen Eco – $9,500 for 10kwh
Panasonic – $1,976 for 2.9kwh

If you break it down to cost per kwh, Tesla is the cheapest and virtually tied with LG, the other two are more expensive for what you get.

Tesla Powerwall – $7,500 for 13.5kwh $600.00 / kwh
LG Chem RESU – $5,900 for 9.8kwh $602.04 / kwh
Sonnen Eco – $9,500 for 10kwh $950.00 / kwh
Panasonic – $1,976 for 2.9kwh $681.38 / kwh
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Re: Solar power direct to home?
Posted by: RAMd®d
Date: August 12, 2022 02:18AM
Hybrid systems are very expensive since you are essentially buying both a grid-tie and an off-grid system.


Some I knew who had a solar installation with the array and batteries.

He stated that once his batteries were charged, any 'excess' went back to PG&E for credit.

I neglected to ask what happens at night or on a sunless day.

Would his house then run on PG&E current, and with the batteries tapped only when AC and solar weren't available?

Or with solar off line, would the house run on battery power until it was low enough that the system then switched to AC?

Battery capacity might affect either scenario, assuming both are possible.






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Re: Solar power direct to home?
Posted by: Bill in NC
Date: August 12, 2022 04:20PM
You can solar power a room (A/C, lighting, outlets) with battery storage for a fraction of the price of installing a whole-home system:

Solar power for your office



Edited 1 time(s). Last edit at 08/12/2022 04:22PM by Bill in NC.
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