Nested Hybrid Inverters (or combining PV from multiple buildings).

longbedbob

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Aug 23, 2020
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Perhaps these seem simplistic questions. My only professional solar experience comes from installing and maintaining remote automated weather stations many years ago. More recently I've added a 12V PV system to my camper. Stepping up to whole house solar requires knowledge of more complicated puzzle pieces.

But back to the topic.

The missus and I recently completed a detached shed with electrical. A subpanel in the shed is tied to the main electrical panel in the house. While I was digging, I ran a second conduit for future expansion, if it's relevant.

Between the house and the shed, we have plenty of unobstructed south facing roof space.

I'd like to start with a small system in the shed. The idea is that, initially, ~ 2kw of solar, some used 48V battery packs and a hybrid inverter could prevent the weekly power "burps" that power cycles everything in the house that needs to be reset. I'd also initially like to have a half day or so of standby power with needing to roll out my multifuel generator.

It would be nice to just route the cabling from my shed to the house in the spare conduit that buried and then install the inverter/charger and battery bank near the main power panel. However, from solar panel to break would be a 150' wire run. That would require some serious expenses in wire and I'm not sure that my 1" conduit could accommodate it.

Complicating matters is that my generator outlet is at the shed. When the grid is down, I roll out the generator to the gas riser I had installed and backfeed power into the house.

As I understand it, a dual AC input hybrid inverter would allow me to use PV on the roof of the shed to charge a small battery bank. It would be wired into the shed's subpanel as would a regular 220v breaker. When the bank was full, the excess power would be backfed to the house without me needing to reconfigure any wiring at the main breaker panel in the house. This excess would be used to lower my monthly electric bill. But when the power blipped or grid went down the battery bank in the shed would be a household UPS for a while. The assumption being that it would safely and automatically return to charging the battery when grid power was restored.

This would also allow me to leave the existing generator outlet where it is without needing to install yet another expensive natural gas riser or the need to make substantial modifications to the wiring.

The problem, however, comes in the future should I expand to add solar to the roof of my house. I'd like to be able to combine the power from both roofs.

Would I be able to use another dual AC input hybrid inverter to do this? Could they both function with one "nested" to create multiple levels of inverters?

I thought that perhaps using a microinverter/small string inverter system for the shed power to then feed AC to the house where it would charge a centrally located battery bank (as opposed to two separate banks). It would make use of the spare conduit and bypass the existing AC house wiring. But wouldn't this be inefficient?

Or perhaps there there is another method for providing short term UPS functionality while keeping longer term expansion in mind?

Thoughts.

Thanks.
 
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