Adjust power factor and save money ...

[wayne.ct]

In browsing the forum it was strongly implied if not stated directly that it would be possible to save a lot of electricity by adding some capacitors, etc. to some home appliances, e.g. space heaters. I would like to have this thread discuss this possibility, including references to videos on the subject, how to investigate the possibility and applicable engineering formulas and instruments that can sift our the details for the experiment-minded hobbyist.

Perhaps to get maximum results in this regard it would be necessary to build custom device. There are plenty of threads here that go down that road. This thread should (hopefully) focus on adjusting the power factor.

The article on Wikipedia Power factor - Wikipedia mentions instruments that can measure the power factor. Is there an inexpensive way to measure the power factor using a common multimeter?

Thanks. I look forward to hearing from anyone who is knowledgeable on this subject.

[Aaron]

power factor correction

Wayne,

For most homes, power factor correction will do little. In Europe and
elsewhere, some fluorescent lights that replace incandescents are
power factor corrected right inside the bulb base. Those aren't in the
states yet I don't think - haven't checked into it for a while. That is a
good thing to have them pf corrected. My friend's parents' fridges
are all very old and were as low as 0.6-0.7 when running. My newer
one is over 0.9 (1.0 being perfect).

Bulk pf correction is the cap placement at your breaker box. It does
work and makes sense but you have to figure out if you're even getting
your money back.

It is highly valuable at the industrial scale for large inductive loads.
Power companies even penalize these customers if their power factor
is too low.

At this industrial level, there are pf units that are extremely sophisticated
and switch capacitance in and out to adjust on the fly. The home ones
with a single cap or few at the box are fixed and are not as good as
on the fly adjustment but that may be expensive at this point to develop
on the fly adjustable pf for something as small as a home.

[wayne.ct]

For most homes, power factor correction will do little.

I guess that is a dead end. There is a lot of information here to wade through. If I happen upon that thought again, I'll come back here and post a link.

[ashtweth]

Hi Wayne/Aaron and Every one

Good timing, as we were given a Kw/Hr house power meter (residential one) to test for this. And we went on TV to comment on the PF correction devices for saving power in the home. Here is what we found.

There are two types of Tariff's to measure power, funny enough some will measure Reactive power (So PF counts, this is industrial areas) others like the residential home meters DONT!.Real power equals V X A X PF. Confused yet?

In the industrial area, if you have poor PF , you get penalized and are required to correct it (as they have to lay bigger cable etc). In the home, we tested the meter to record KW/Hrs with poor PF and leading PF and guess what?

All households are charged on kWh or the actual power used by a particular load over a period of time (hours) NOT the power supplied to the house or apparent power (so reactive power losses gets discarded!). The meter did not flinch, we had poor PF, leading and it still didnt change in recording power. so the power companies are telling the truth in this case.

when you add a power factor device to the home.The supplier may mention I2R (or I squared R) which is current squared X the resistance losses. These losses in the home are like the industrial area, losses in cables etc due to resistance in cables.There are reduced because of the current reduction and therefore result in real power reductions. These in a house hold may be very small, so Aaron is right. 1-5%, depends on some factors.

In plain English, the PF boxes at the grid of the house only reduce the cable losses and save a small amount, the reactive power you waste or dont use in the house does not get recorded by the meter! So the power company does not charge you for poor PF only Kw/hrs on actual power used. Confused yet?

Those power factor boxes wont save as much as what they claim, However they do reduce the NETWORK cost of delivering power and are a good idea IMO. But they should be the responsibility of the power company , NOT the consumer.

Ash

[FRC]

Device

There are devices which measure current draw. I have a small one that you plug into the wall, then plug your appliance into and it tells you how many watts, etc. you are consuming. I have reduced my consumption quite a bit by
switching to LED light bulbs and 12v joule thief type cfl circuits.

FRC

[ashtweth]

Hi FRC, do you know

House power = kWh (kilo watt hours) Power is V X A X PF
When you add caps
V X A(change) X PF (change) = savings right?

The power supplied to create kWh is KVA, but when the kW change with PF correction the KVA stays the same! They cancel each other out! This is a very confusing area, i have included the KVA/Kw equations below, the most confusing for us was how it doesn't matter if your PF AND amps are reduced in the home, THE HOUSE POWER BOX DOES NOT RECORD THE CHANGE!. I know its confusing, but your HOUSE meter doesn't read PF correction "savings" if that makes any sense? Its a good idea tho, you would prob increase the life of your appliances. Less heat maybe etc etc.

I was dumb founded. As we saw the amp draw drop on the WALL METER, but whether the PF correction was bad or good and reduced the amps it was not recorded as savings by THE HOUSE METER BOX (where you get charged for your bill).

The meter is not designed to penalize you for bad or good PF as power savings, the reactive component is discarded out of the HOUSE METERING SYSTEM all together!. So if you have good or bad PF and you reduce your amp draw it will not record this! Only record "real power" used by the device.. Yes my head hurts too. Read below Let me try another way to make our head hurt, i would rather just have a beer an work on the Lockeridge device!

If the device does some thing like reduce the voltage or frequency of the power supply like this device Voltage Optimisation Cockburn Powerstar Energy Management Systems then it could have a greater then 1% effect etc,but since households are not charged for DEMAND POWER, then the PF correction should make minimal difference (only reduce losses in cables for savings).

So correcting the power factor (PF meter box) will reduce the current drawn from the street, supply and this reduces the KVA (kilo volt amperes) or apparent power of an installation. HOWEVER the KW (kilowatts) or "real power" is not effected as shown by some simple formulas below.

Basic formula for power factor =kW/KVA (e.g 100kW at a power factor of .08-KVA =125).

kW=(volts X Amps X pf)/1,000
KVA =(volts X amps) / 1,000

ALL house holds are charged on KWh (kilowatt hours) or real power or the actualy power used by a particular load over a period of time not the power supplied to the house or apparent power

EXAMPLE

A single phase air conditioner drawing 10 amps with a .07 power factor

kW =(240V X 10 X 0.7)/1,000 (if run for an hour this would be 1.68kWh and if the kWh on the bill was 12c/kWh then the cost per hour = 0.20c.

KVA = (240 X 10)/1,000 = 2.4KVA. THIS IS THE APPARENT POWER THAT COMES FROM THE STREET THAT IS SUPPLIED TO PRODUCE THE 1.68kW

Improving the power factor (using a capacitor) to 0.99 will reduce the KVA to 1.69 KVA and the current to 7.04 amps.

kW =(240 X 7.04 x 0.99)/1000 = 1.68kW - NO CHANGE TO THE "REAL POWER" AND THEREFORE NO COST REDUCTIONS.

We filmed the house meter on a cap box, and will have a video for all soon.
The supplier may mention I2R (or I squared R) which is current squared X the resistance losses. These losses in the home are like the industrial area, losses in cables etc due to resistance in cables.There are reduced because of the current reduction and therefore result in real power reductions. These in a house hold may be very small, so Aaron is right. 1-5%, depends on some factors.


Ash

[ashtweth]

Bump sorry guys missed a lot of edits, please check new info above

[FRC]

Savings

My last bill was adjusted actual reading. They took off $137.00 in false estimates. This was winter months, but I also stopped using a big old freezer.

FRC