Power Factor correction for solar system

[elkowalski]

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]

No such thing using an inverter, or anything you could do about it.

[russ]

Hi Sunking,

As I understand it, consuming devices with a poor power factor can cause you to draw additional power from the DC side.

Could be of interest with a battery system in particular.

No correction involved except replacing consumer units?

Russ

[Mike90250]

There is no easy fix for homeowner scale PF correction. Large industrial installs, have banks of auto switching capacitors, which cost a fair amount. If you add a cap to a home, it's always on-line, affecting power factor, when the loads may not be running. If you install on a motor, you risk voiding the UL listing of the motor, or burning of the motor relay contacts.
And for CFL bulbs that are lame, you can't fix the PF for them with anything but a new driver circuit.

[russ]

I have purchased (signed the PO anyway) for several large scale PF improvement capacitor banks over the years. Those plants were consuming about 100 mW total with many large (1.5 to 3.5 mW motors). The power was supplied from our captive power plant so it hit close to home.

The only practical method for the homeowner to do any PF improvement, as you point out, is to replace the offending appliance/equipment.

One problem is that last time I checked many manufacturers consider PF information as top secret. At least with CFLs and LEDs.

The consumer is caught between a rock and the hard place.

Russ

[Sunking]

Hi Sunking,

As I understand it, consuming devices with a poor power factor can cause you to draw additional power from the DC side.

Could be of interest with a battery system in particular.

No correction involved except replacing consumer units?

Russ

Russ the problem is PF correction is dynamic and ever changing with load demands. Industrial capacitor banks are constantly switching in and out capacitors to compensate for changing load demands. No consumer could afford it, nor is there such a small toy made for residential systems. Not many home owners have multiple 10 to 100,000 horse power motors.

[russ]

Nothing can take care of adjusting the PF in a residence on a practical basis - agreed.

But, some lamps and other consumers are worse about PF than others. If people had an idea of the PF of a brand of CFL for example they could select the more suitable model/brand.

With a grid tied system it wouldn't make any difference anyway as normally a residential consumer is billed for kWh. Only with off grid would it make any difference.

[Naptown]

Nothing can take care of adjusting the PF in a residence on a practical basis - agreed.

But, some lamps and other consumers are worse about PF than others. If people had an idea of the PF of a brand of CFL for example they could select the more suitable model/brand.

With a grid tied system it wouldn't make any difference anyway as normally a residential consumer is billed for kWh. Only with off grid would it make any difference.

Could you expand on that a bit more?

[Mike90250]

Could you expand on that a bit more?

Sure, with top of the line household sine wave inverter, say, 3KW, if you install 2KW of CFL bulbs, you will overload the inverter, as most CFL's have power factor of .6 or less.
The inverter does not have the resources of Hover Dam behind it, and cannot supply the power that the lousy PF CFL's demand. If they were well pumps, you could fine tune them with Run capacitors to get the PF to .9, but the driver circuits need a complex solution to cure their low PF . This has already been discovered in Europe, and bulbs there need to meet a PF spec. LED lighting also has the same PF problem.

http://cdonner.com/power-factor-and-compact-fluorescent-bulbs-cfl.htm

http://homepower.com/article/?file=HP96_pg128_Letters_1

http://greenerlights.blogspot.com/2009/03/3g-cfl-analysis-power-factor.html

http://open4energy.com/forum/home/scam/cfl_power_factor

So, in a grid situation, it likely evens out, but off grid, when the inverter reaches it's limit, that's all.

[Naptown]

don't have solar on my house ( trees and the tree huggers won't let me cut them even though they are my trees)
I do however use a lot of cfl bulbs.
Would I achieve better savings by switching to a higher PF bulb and where do you find out who's are the better ones.

[Mike90250]

Would I achieve better savings by switching to a higher PF bulb and where do you find out who's are the better ones.

You have to searcht he web, or use a kill-a-watt to measure

[Sunking]

don't have solar on my house
I do however use a lot of cfl bulbs.
Would I achieve better savings by switching to a higher PF bulb and where do you find out who's are the better ones.

No Rich it is of no concern to you whatsoever, the POCo does not charge you for VARs. You do not use enough for the POCO to worry about. It is industrial customers who get to worry about it as it can be as much as half of their electrical load and they do get charged for VARs, or penalized is a more accurate description.

What you do need to pay attention too is efficacy or lighting efficiency as this varies quite a bit with CFL lamps expressed as Lumens/watt.

[russ]

From what I understand, (my understanding is sometimes correct and sometimes not so correct on electrical matters) - with grid tie it will not save a customer any money - as Sunking points out residences are almost always charged per kWh with no consideration for power factor.

With off grid where you are your own and only electrical supplier it would become more important.

Russ

[elkowalski]

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?

[russ]

Not really - It is important that you use devices such as lamps with a good power factor.

A pump motor may benefit from capacitors but they are dedicated to the pump run circuit and only in use when the pump is on.

RUss