Understanding microinverters

[pmeloy]

I'm researching adding solar to my home. I had some solar in my travel trailer years ago (simple 12V system) and I'm a former Marine Engineer/Civilian Operating Engineer (not the college boy but the ones operating machinery). So I have a good understanding of electrical (though nowhere near that of an actual electrician).

Putting in a single String inverter/charger system is pretty simple but I don't like having lots of large guage wiring and only 10 years warranty so I'm looking at microinverters but I'm just not understanding the grid tie/power outage functionality.

If I am grid tied it looks like the microinverters will isolate so no power is pushed onto the grid to electrocute any unwary electricians working on a powered down line. That is good BUT that would mean that on a sunny day when the grid is down (happens pretty much weekly here in the Philippines) Do I get no solar power at all?

 

[sunshine_eggo]

String inverters tend to be high voltage, so it's rare that you'll see more than 10awg on a string inverter.

Generally, for all grid tie w/o battery: grid down = no power.

SOME microinverters can be isolated and will work purely on PV. The IQ8 is the only one that comes to mind.

Note that your DC to AC inverters are on the roof under a hot solar panel. There is concern about their durability/longevity.

 

[fafrd]

String inverters tend to be high voltage, so it's rare that you'll see more than 10awg on a string inverter.

Generally, for all grid tie w/o battery: grid down = no power.

SOME microinverters can be isolated and will work purely on PV. The IQ8 is the only one that comes to mind.

Note that your DC to AC inverters are on the roof under a hot solar panel. There is concern about their durability/longevity.

Uh, I think you have that wrong.

Pretty much ALL modern Microinverters can function off-grid as long as there is a PSW / hybrid inverter providing a suitable grid signal.

Older PSW inverters that don’t support frequency shift will not work well since they either have to absorb 100% of Microinverter-generated power (charging a battery, for example) or shutting everything down with out-of-range frequency.

But any of the new-generation hybrid inverters supporting frequency-shift such as Victron Multiplus II, Schneider Conext XW+, or Solark can modulate Microinverter output power to match demand using frequency shift.

Another alternative is the Hoymiles Microinverters which use an energy meter rather than a hybrid inverter to command Hoymiles Microinverters to output just enough power to zero-out consumption without exporting any power to grid.

The magic is not in the Microinverter but rather whatever is controlling it’s output…

 

[sunshine_eggo]

Uh, I think you have that wrong.

Nope. When the IQ8 are paired with a IQ System Controller 2, they will form their own grid and provide loads with PV only.

Pretty much ALL modern Microinverters can function off-grid as long as there is a PSW / hybrid inverter providing a suitable grid signal.

Older PSW inverters that don’t support frequency shift will not work well since they either have to absorb 100% of Microinverter-generated power (charging a battery, for example) or shutting everything down with out-of-range frequency.

But any of the new-generation hybrid inverters supporting frequency-shift such as Victron Multiplus II, Schneider Conext XW+, or Solark can modulate Microinverter output power to match demand using frequency shift.

Another alternative is the Hoymiles Microinverters which use an energy meter rather than a hybrid inverter to command Hoymiles Microinverters to output just enough power to zero-out consumption without exporting any power to grid.

The magic is not in the Microinverter but rather whatever is controlling it’s output…

Did you get the impression that the OP is planning to install two systems, or did you get the impression they are simply looking at microinverters alone and is curious what happens when the grid goes down? I didn't see anything about an existing system in place to form a suitable grid for the microinverters.

You start talking about a second inverter of equal or greater power capable of AC coupling/frequency shifting and batteries in addition to grid tie, and the expenses go up pretty dramatically.

For the OP if you would like to read more about what it takes to make a GT system work when the grid is down, here you go:

AC Coupling

AC Coupled Solar Power System - use your existing system to feed power into a battery based inverter/charger to charge the battery bank.

www.altestore.com