Power Factor correction for solar system

[Sunking]

therefore since i have a off grid system it would be important to add a pf correction after my inverter so that i dont waste some of the energy that might go to heat the wires isnt it correct?

No not correct as there is no device you could buy to do any good. As Russ states you need to buy utilization equipment with POf correction already built into it.

As I stated before PF is dynamic and ever changing, no device you could buy or at least afford to buy can is dynamic and active. The higher quality battery inverters already have PF correction built in, not perfect, but better than anything you could add.

[swtdir]

Power factor correction

It seems to me that it should be possible for a smart system to measure load power factor and send a phase adjustment signal to the solar inverters and have them do dynamic power factor correction so the load to the power company is closer to 1.0. I assume the electric company meters actually measure volt amperes and bill for those rather than true kilowatts. Thoughts?

[inetdog]

I assume the electric company meters actually measure volt amperes and bill for those rather than true kilowatts. Thoughts?

Actually, standard residential meters measure only true power (watts).
This is why the common adds for PF correction equipment for residential use are bogus.
For some commercial/industrial customers POCO will install a meter which records both KW and KVA or both KW and worst case Power Factor. The billing in that case is typically still based primarily on KW, but with a separate penalty for excessively low PF.

[russ]

It seems to me that it should be possible for a smart system to measure load power factor and send a phase adjustment signal to the solar inverters and have them do dynamic power factor correction so the load to the power company is closer to 1.0.

Solar is a small fraction of all generation most places and already all parties are subsidizing the few that have the systems. Don't think this will happen in the near future.

Residential solar will always be small potatoes I believe.

[swtdir]

Thank you guys

Solar is a small fraction of all generation most places and already all parties are subsidizing the few that have the systems. Don't think this will happen in the near future.

Residential solar will always be small potatoes I believe.

Interesting, and a surprise that residential meters measure true power. I don't know what our house measures but when I go around with the Kill-A-Watt meter and measure individual pieces, I am usually surprised how low the PF is. We have a 2KW Enphase/Grape Solar/Costco grid tie being installed at present, otherwise the only solar is an attic vent fan tied to a Harbor Freight panel. The obvious next question is a change-over capability to use the 2KW Enphase on a battery backup if there is a real emergency. The discussions on the Enphase Forum are not promising.

[Mike90250]

....... next question is a change-over capability to use the 2KW Enphase on a battery backup if there is a real emergency. The discussions on the Enphase Forum are not promising.

No way a inverter can easily tell if it's being fed by a battery @ 90V / 3 amps or a PV panel @ 90V / 3 amps, unless it monitors the stability, and sees the battery is very stable compared to the PV. When it does it's MPPT search/test, it won't find much to track with a battery, and that may make it fail the qualification. But if you put a power resistor in series with the battery, waste some power as heat in the resistor, it may make the battery look more like PV. Maybe.

[Naptown]

The only way to do back up with an Enphase system is AC coupled. This presents it's own set of challenges with keeping the batteries from over charging when solar exceeds the demand and batteries are in float.
It will also void the Enphase warranty.

[swtdir]

Agreed

The only way to do back up with an Enphase system is AC coupled. This presents it's own set of challenges with keeping the batteries from over charging when solar exceeds the demand and batteries are in float.
It will also void the Enphase warranty.

The 2KW Grape Solar Enphase setup uses 8 x 250 watt panels and 8 inverters paralleled. So yes indeed to the AC coupling and the Enphase folks make it clear they will not warranty such a setup worked into a generator or AC inverter. Still, it seems there should be a way. Should we be in another area since the power factor question was answered succinctly?

[russ]

The 2KW Grape Solar Enphase setup uses 8 x 250 watt panels and 8 inverters paralleled. So yes indeed to the AC coupling and the Enphase folks make it clear they will not warranty such a setup worked into a generator or AC inverter. Still, it seems there should be a way. Should we be in another area since the power factor question was answered succinctly?

Actually we try to stay away from the "shade tree" and not legal solutions - don't post them here.

[SunEagle]

hi guys, i have doubts about power factor regarding solar panels would it be good to add a power factor correction to the power inverter so that we dont waste energy in the wiring. am i in the correct track? or adding the power factor correction wouldnt be that good to the system?
any suggestions are appreciated.
thanks in advance

Sunking is correct. The power factor is very dynamic due to the ever changing electrical load. Installing an automatic PF capacitor system is very expensive and not worth the cost to a home owner.

But even if your system was a commercial or industrial I would advise not installing just any type of Power Factor capacitors to the inverter circuit. The inverter is already a source of harmonic distortion and just adding the PF capacitors without the correct harmonic filtering will increase that distortion. The minimum results would be making the power factor worse which does not save you any money. The maximum results could lead to equipment overheating and failure.

[swtdir]

Shade tree

Actually we try to stay away from the "shade tree" and not legal solutions - don't post them here.

Certainly proper since there is a safety question. The Enphase forum took a correct turn in saying Enphase should study it and come up with a recommended approach that they can warranty. The major question of backfeed certainly requires a transfer switch, the other questions of stability and psuedo linear operations where panels, inverters and batteries are often driven into non linear regions make it pretty difficult to understand a configuration which would be reliable and stable and does not risk blowing up inverters, batteries or generators. Are you saying we should not even talk about it?

[russ]

Certainly proper since there is a safety question. The Enphase forum took a correct turn in saying Enphase should study it and come up with a recommended approach that they can warranty. The major question of backfeed certainly requires a transfer switch, the other questions of stability and psuedo linear operations where panels, inverters and batteries are often driven into non linear regions make it pretty difficult to understand a configuration which would be reliable and stable and does not risk blowing up inverters, batteries or generators. Are you saying we should not even talk about it?

The Enphase forum said what? a little BS and blather to make you happy and neatly disposed of the idea. They will do nothing of the sort.

I am saying no 'shade tree solutions' are to be posted.

[swtdir]

Agreed

The Enphase forum said what? a little BS and blather to make you happy and neatly disposed of the idea. They will do nothing of the sort.

I am saying no 'shade tree solutions' are to be posted.

Sorry if referring to the Enphase Forum gave the impression they condoned the idea. There are comments by users are to that effect, that Enphase should study the question, an attempt to put a little pressure on them to do that.

[Mike90250]

..... I am saying no 'shade tree solutions' are to be posted.

Reason being the possibility of lawsuits in the USofA, if someone ponders a solution, and some body else acts on it, thinking it "gospel" and then burning down the house when it does not work well. Oh, nobody took the pet rock out of the house - Lawsuit.

So we can discuss Mfg's recommendations, and what they should add, but it's really tough to offer solutions that are too far out of the box, or ways to bypass national electric code. Sucks, but that's what the "Nanny State" has brought about.