Yet Another Reason to Dislike CFLs: Horrible Power Factors

Apr 9th, 2009 | By | Category: Dear Science Column, Environmental

Many of you already know of my skepticism of compact fluorescent lightbulbs. Now utilities are joining in the hate: CFLs use about twice as much energy than previously claimed.

Lightbulbs, TVs, ovens, baseboard heaters–whatever–draw energy from alternating current with varying degrees of efficiency, due to the funkiness of alternating current.

Allow me to explain, by taking us all bowling. Kinda.

We want to pump up a tire with a foot bicycle pump down on the far end of the bowling lane. We screw the pump down on its side, and aim with our bowling ball. We hit it, and it shatters into pieces. No good. Marbles would be safe for the pump, but getting them all the way down the alley is next to impossible. They slow down and stop due to friction almost immediately, where the heavy bowling balls have enough momentum to make it all the way to the end. Now what?

We get a clever idea: Let’s line up a whole bunch of bowling balls in the gutter, placing the last one on the handle of the pump. On our side of the lane, we put a spring on the end of the line of bowling balls. We pull back our spring, a little bit, with the first ball and then let it go. The energy is transferred to the far end through each ball. The last ball at the end of the line presses down on the handle. Some of the energy transferred goes to pump up our tire; the rest goes to compress the pump’s spring. Eventually, the pump spring gives back most of this stored energy, sending the bowling balls back to our spring. Since some of the energy was used up, we pull our spring back a bit more, and release it again. We now have waves of energy successfully transmitting from our end of the lane to the pump’s end: Alternating current.

(If this doesn’t make sense to you, you should feel really thankful for Nikola Tesla. Without his genius, you would be cold and hungry right now.)

What the power company is doing is constantly adding energy back into the spring at their end of the chain of bowling balls (electrons, unpacking our metaphor). A/C devices with a perfect power factor of 1.0 act as perfect springs: all of the leftover energy delivered is returned in phase back to the power plant. Compact fluorescent lightbulbs mess up the line of bowling balls like an obnoxious kid. When the wave is outgoing, they push in on the chain a little bit; when incoming, they push outward. CFLs make a portion of the alternating current go out of phase. The bowling ball waves still work, but it takes the power company more effort to keep each wave going.

About half the energy used up by a CFL goes to this naughty out of phase game. While there are ways of designing well-behaved CFLs, most companies making them (typically in China, with factory workers twisting hot glass filled with mercury powder by hand) don’t exactly seem interested. As per Better Off Ted, the corporate motto is, “Money before people. It’s engraved right there in the lobby floor. It just looks more heroic in Latin.”