Power Factor

Anyone know much about power factor? I have noticed that there is a lot of wasted power in micro power generation too. When you look at the amount of power generated by solar panels into batteries during the day I think there is about 20% loss..

There is loss of power generated in wind and solar panels but there does not seem to be much talk about this subject on forums..

I would also think that batteries have a loss too when you are charging them.

Hi Victor,

I think a good example of a power factor might be say using a DC motor to send energy to a battery.

example,

"Look at me, I have a 150 watt wind generator as it is producing 30v open, and 5 amps current".

The above is true if you have a 29.5v battery, and then it is only 147.5w wind generator, but no such thing as a 29.5v battery obviously.

At 24 volts, it becomes a 117.5w wind generator,
At 12 volts, it becomes a 57.5w wind generator,
and 6 volts, it becomes a 27.5w wind generator.

The above assumes the battery is flat, the diode is not dropping the voltage, and +.5 volt is required for charging.

Batteries do not convert over voltage and amps to watts, they simply require a greater voltage then what they have for charging, the amps or lack of amps dictate charge time to a point.

The same is true - power factor - for solar/pv, a 100 watt panel is generally rated at 18v open, meaning at 12v (no charge controller) it is now only a 66ish watt panel, at 6v (no charge controller) it is a 33ish watt panel.

I think,
Tim

"Power Factor" is not what you think it is. It is related to AC and reactance.

Solar panels are current supplies. They can supply X amps at 0V or 17V.
(I believe 17V is more commonly accurate than 18V).
Buy a panel by amps.

I think the topic you want to look for is "MPPT".
For wind, be prepared for reading very long 3-way arguments about stuff you cant understand.
I decided (1/3 x 1/3 =) 11% of it is correct... Best I can say.
G-

Edit: "stuff You cant understand" was not aimed at anyone in particular.
"stuff Nobody can understand" is how that should be taken.

Hi ghurd,

Yep, when I google power factor, wickipedia states the same as you, so we know you are correct.

The internet is a great thing, instant knowledge at our fingertips :)

Best,
Tim

Superb posts!! Thanks everybody...

Power factor is the ratio of KW to KVA and is usually applied to AC loads to indicate the losses in the power transmission.
Power factor is often considered as the angle between voltage and current (displacement power factor) but is also related to distorted waveforms (distortion power factor).
Take an one amp DC current applied to a load via a one ohm resistor. The voltage drop across the resistor is one volt and so the power loss is 1 x 1 = 1 watt. Now add a switching type regulator with a higher current to regulate the current to a one amp average.
If we have two amps for half the time, i.e. 10ms at 2 amps and 2 ms at 0amps, we have an average of one amp. Our power loss during the 2 amp cycle is 4 watts, and the power loss during the 0 amp cycle is 0 watts. The average power loss is (4 + 0) / 2 = 2 watts. This is an example of distortion power factor.
For more information on power factor, see htp://www.LMPhotonics.com/pwrfact

Best regards,

Mark Empson
http://www.LMPForum.com | http://www.LMPhotonics.com | http://www.markempson.com

Mark,
Thanks for the insight, however,
I dont appreciate so many external links from a first time poster.
Not a worry this time, as you clearly know what you are talking about.
I welcome you to our forum.

Ben.

I found marke `s links very informative and beneficial to the forum.. It explains to me a lot of things clearly ...Thankyou marke and a Big Welcome to Ben`s forum!!!!!! :-)

ghurd knows exactly what power factor means, for the rest of us the simple answer is that power factor is the difference between the phase angle of the current and the voltage with respect to the actual work being done by AC waveforms. To understand this you need to move beyond algebra and the simplified version of ohms law and move to calculus and "complex" math, but to keep it simple, in a purely capacitive or purely inductive circuit the voltage leads or lags the current by 180 degrees, and in theory, no "work" is done. If you simply measured the peak current and multiplied it by the peak voltage, you would get a very misleading representation of the power being consumed or produced. Power Factor is directly linked, though not necessarily a linear function of efficiency, in an AC electrical circuit. I think Victors question is actually about efficiency, and has little to do with Power Factors, so i will not expound further on PF.

Victor, there is a tremendous amount of discussion about the efficiency of "alternative energy" in this and all AE forums. Efficiency and storage are the evil subverters of AE. They are the crux of almost every sensible discussion about wind or solar power conversion. At the end of the day, if you can convert 25% of the available solar energy (wind IS solar energy) into electrical power, you have truly achieved something. If we start from the "source" (ie, the SUN) a more realistic efficiency would be more on the order of magnitude of 10^-12; that is to say, we can convert ~ 1 part in 1 trillion /M^2 of the available energy to electricity, and that estimate is +/- 10^-6 depending on where you take the initial measurement from. If we start at the Suns surface then our efficiency 90+ million miles away is less than if we start at the stratosphere where only a tiny portion of the energy from that M^2 actually lands. None of this means that solar energy is trivial, on the contrary, the amount that lands around us every day is phenomenal, but capturing 25% of what actually "lands" in our backyard is a tall order.

Hope this helps :-)

Fish