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Utilities suffer from CFLs poor power factor

rjoh878646
15 years ago

Found this article on electronic design news about power companies suffering from the low power factor of CFL's

Article below Link at bottom to article and comments.

Monday, April 6, 2009

Utilities suffer from CFLs poor power factor

Apr 6 2009 6:00PM : Permalink :Email this:Comments (23) :

Every CFL light contains a small ac-dc power supply with reactive components in it that will affect the CFLÂs power factor (PF) Â that is, the load presented to the ac line. The closer the PF is to 1, the better. A load with low power factor (<.85 draws more current and is less efficient than a load with high power factor for the same amount of useful power. higher currents required by lower pf devices mean increased energy lost in grid due to such things as i2r losses. these losses don show up directly on our electricity bill but utilities sure see effects.>I put one of my home CFL bulbs on my Kill-O-Watt power meter recently and measured its power factor: It was .57. This is lousy. Although each CFL is only 13W, there are millions of them out there. Why no PF regulation, as there is of higher-power, but less ubiquitous devices?

I emailed Peter Banwell of the EnergyStar program and asked if EnergyStar was considering making minimum PF a requirement for Energy Star compliance. He replied, "We looked at this in detail several years ago and decided against it, though there are a couple of utilities that still support the idea. We may take this up in the future, as the market share grows, but right now it is still in the noise in terms of impacts."

Coincidentally, after our email exchange I ran into Mike Grather of Luminaire Testing Laboratory. He recently ran a series of life-cycle and performance tests on a batch of 100 CFLs with various power ratings averaging approximately 20W each. They assumed a PF for the lights of at least .75 and sized the power supply at 3KVA. However, when they powered up the bank of CFLs, the 3KVA supply was inadequate. Grather checked the power factor for the CFLs and found they ranged from .45 to .50. Their "real" load was about twice that implied by their wattage.

CFLs are still an efficient form of household lighting, but their poor PF number is leaving money on the table. However, itÂs clear that at about $2 each thereÂs not a lot of room for adding power factor correction circuitry. On the other hand, utilities are already going to great lengths to encourage consumers to switch to CFLs, including subsidizing the price of CFLs. I doubt that consumers would be interested in paying more for a feature that actually benefits the utility directly, not them. Perhaps utilities will start to subsidize high-power-factor CFLs, rather than the mediocre ones we can buy now.

Related entries in: Power Sources/Controllers :

Here is a link that might be useful: EDN article

Comments (19)

  • pharkus
    15 years ago

    ... that's nice.

    Just pulling some numbers out of your post, the 20W CFLs are typically advertised as having similar light output to a 60W incandescent. Sooo... 100 60W bulbs would require 6kW. Since the PF of a resistive load (like a light bulb) is 1, a 6kVA power supply would be needed (higher, actually, provided the lamps represent a continuous load), rather than the 4kVA needed for the CFLs (twice the load implied by their wattage = 2x[100x20] = 4000)

    Looks to me like CFLs, even with "lousy" PF values, are still an improvement over the incandescents they are marketed to replace, and the utilities' encouragement does, in fact, make sense.

    Again, this is only based on numbers stolen from your post, and is of the same accuracy.

  • fa_f3_20
    15 years ago

    Well, even if the power factors of the CFLs are that bad (which surprises me), I suspect that many homes today often have leading power factors due to all of the electronics in the house. So (except for when heavy motor loads, like A/C, are running), it could be that the CFLs are actually improving the power factor of the house system overall.

  • fotostat
    15 years ago

    A Kill-O-Watt measures power factor?

    I've been using CFLs for many years. 13W CFLs equal 60W incans. 17W CFLs equal 75W incans. And 21W CFLs equal 100W incans. That's an average, some odd brands are plus or minus 1 watt.

  • Ron Natalie
    15 years ago

    The variation is that for neither CFL's nor for regular incandescent bulbs is there a strict correlation between watts and light output. The biggest lies are on the new LED replacements. The lumen output of their so called "75W" replacements is half of the typical incandescent

  • gblentz
    15 years ago

    We just need the US government to impose "minimum power factor standards" on all transformer-based devices... that'll fix everything. :-b

    >A Kill-O-Watt measures power factor?

    Yes.

    >The biggest lies are on the new LED replacements. The lumen output of their so called "75W" replacements is half of the typical incandescent

    As a consumer, I wouldn't mind seeing "lumens per watt" and "lumens per VA" numbers required on the box for light emitting devices.

    Or how about just require a published "Power Efficiency Ratio" (PER) for all electrical devices, that lists how much energy is actually used for the device's stated function, and how much is wasted as heat? If nothing else, it would educate the consumer to the fact that there's no free lunch, and that they're paying for their "cheap" lighting and electronics on the back-end when they receive their electric bill (doubly so during air-conditioning season).

  • Ron Natalie
    15 years ago

    Most of them have the lumens (you can divide the watts yourself if you care) that the bulb puts out. I believe for incandescents you always get the wattage, bulb life, and lumesn listed. Some of the "alternative" hide the info a bit, but if you hunt for it, it is there.

  • gblentz
    15 years ago

    It is getting better, but I don't know that I'd say "most" have lumens listed yet.

    Furthermore, there's been more than one instance where I've seen company-A's packaging claim that their 100W incandescent bulb put out, say, 1650 lumens, and company-B's claim that theirs put out 1780. Only thing is, company A rated their bulb at 120v, and company B rated theirs at 130.

    Way back, I even once had a brand's standard and "long-life" bulbs list different voltages as well as lumens (the standard bulb being higher in both cases) but give the same ohm reading! Same bulb? Who knows.

    My point is, when a lumen rating has been listed, there has historically been a general lack of consistency in standardization, if not outright fudging, of the numbers.

    And when it comes to CF's, and power factor comes into play, the waters get even murkier. True, the meter measures kWH's, not kVA hours. But in the end the customer ends up paying more for lousy PF anyway, since it still costs the utility more on their end, and that cost is ultimately passed on in the form of higher per-kWH rates.

  • brickeyee
    15 years ago

    "Way back, I even once had a brand's standard and "long-life" bulbs list different voltages as well as lumens (the standard bulb being higher in both cases) but give the same ohm reading! Same bulb? Who knows."

    Did you calculate the resistance based on measured voltage and current or slap on ohm meter across the bulb?

    Incandescent filaments change resistance significantly as they heat up.

    The 'cold' resistance is lower than the resistance at operating temperature.

    Many an EE has blown a drive transistor by using the resistance of a cold filament to size a transistor (or triac) controlling the bulb.

  • willinak
    14 years ago

    Slightly off subject, but this thread has been an eye opener for me, and is just another reason that I despise the CFL mandates. I have tried several brands, mostly from Costco and they are just junk. I always date the replacement bulbs and found their lifespan is all over the place. Where I have a mixture of incandescents on the same circuits, the CFL's get replaced as often if not more often as os the incand's.
    I think the CFL is a good idea, but in reality, they don't cut it. Let's instead spend our money developing LED manufacturing.

  • mikie_gw
    14 years ago

    I don't think I have any incadescent lightning left except for one uplight quartz pole light that so seldom gets turned on the dust on it caught on fire once.

    CF cheapy HomeD twisty bulbs and some floods which are just the same twisty's in a wrapper here sure do last a long time on photo cells burning all nite, every night. The lights in the bathrooms are slow to brighten after some age but they last forever it seems.

  • dave100
    14 years ago

    "Incandescent filaments change resistance significantly as they heat up.

    The 'cold' resistance is lower than the resistance at operating temperature.

    Many an EE has blown a drive transistor by using the resistance of a cold filament to size a transistor (or triac) controlling the bulb. "

    Brickeyee, the logic of your last sentence is inverted from the explanation of the previous one.

  • brickeyee
    14 years ago

    "Brickeyee, the logic of your last sentence is inverted from the explanation of the previous one."
    Corect, sorry.
    Larger loads are often driven by connecting the bulb directly to the supply.
    The transistor is than placed in series with the bulb to ground.
    When the transistor turns on the filament is at a lower resistance than the wattage of the bulb indicates.

    This causes more current to flow through the transistor when the bulb is first turned on, blowing the transistor.

    One of Murphy's Laws corollaries is that transistors always blow to protect fuses.

  • billhart
    14 years ago

    Perhaps it should read: Many an EE has blown a drive transistor by calculating the resistance and current from the bulb's wattage to size a transistor (or triac) controlling the bulb.

  • brickeyee
    14 years ago

    Back to the power factor problem of CFLs.

    The POCO issue is that they cannot bill for the poor power factor.

    The generation and distribution system must be designed to deliver the V-A required, not just watts.

    The poor power factor increases the size of all the equipment and line losses on the distribution side, with no way to bill residential customers.

    If the waveform is non-sinusoidal (and switching power supplies are unless power factor correction is done in the equipment) it can also lead to nasty harmonics and overloading of lines.

    The bad power factor of PC power supplies started causing all sorts of problems a few years ago.
    The result was a standard that requires them to correct the power factor in the supplies.

  • texasredhead
    14 years ago

    I find this conversation interesting if a little over my head. CFLS, LEDs, and energy effecient appliances, A/Cs, etc., have the effect of lowering energy consumption. As electric utilities see consumer demand decrease so will their income stream.

    A similar example; several years ago there was a concerted effort on the part of the city owned water utility to reduce lawn watering and water consumption. The conservation effort worked so well, the city raised its water rates to make up for the loss in revenue.

  • brickeyee
    14 years ago

    "...lowering energy consumption..."

    That is only part of the problem.
    If you dissipate 100 Watts (=100 V-A) with an incandescent bulb, the power factor is 1.0 and the POCO bills for very thing consumed.

    If you use a 50 W device with a power factor of 0.5, the POCO has to size all the equipment for the 100 V-A load, but can only bill for the 50 W dissipated.

    Everything from the generators to the distribution wiring must be able to carry 100 V-A.

    It also causes odd harmonic currents that can actually overload the neutral in a 120/240 V single phase. or a 3-phase system.

  • pharkus
    14 years ago

    As usual, someone isn't paying attention to the big picture.

    A 100 20W CFLs gives the same light as 100 60W incandescents.

    Due to power factor issues, those CFLs require a power supply sized for 4000W, but the equivalent incandescent load is 6000W.

    The CFLs are STILL an improvement! Quit whining, or re-post numbers that actually PROVE the point, rather than DISproving it! Using the numbers rjoh878646 posted (which I have made no attempt to verify), utilities aren't suffering at all. They get to use 4kVA worth of equipment to give the equivalent light output of 6kW of incandescent bulbs.

  • brickeyee
    14 years ago

    "...rather than the 4kVA needed for the CFLs (twice the load implied by their wattage = 2x[100x20] = 4000) ..."

    It is right here.

    The POCO needs to provide twice the rated capacity in the distribution network, yet can only bill for half.

    It is not always about saving power when things occur on a large scale.
    The CF lights save power compared to incandescent.

    They also create problems for the grid with their lousy power factor.

    As they come into wider use, expect to see rules passed to require power factor adjustment, just like happened with PC power supplies.

  • pharkus
    14 years ago

    True that, I was looking at things from the wrong person's perspective, and thinking in terms of power rather than money.