CFL vs. incandescent: Battle of the bulb

Industry News

SOURCE : CNLEDW.COM 2009-7-8

Compact fluorescent light bulbs are often mentioned as one of the easiest ways to shrink your power bill and your carbon footprint. They present the quintessential green-green situation: saving money and helping the environment. What's not to like?

There's the higher retail price — who wants to pay three bucks for a light bulb when it's sitting right next to ones that cost less than a dollar? But the CFL can last up to 10 times longer than incandescent bulbs, meaning you'd have to buy 10 of them during a single $3 CFL's lifespan. Each CFL saves about $30 during its tenure, according to the U.S. Energy Star program, and pays for itself in about six months.

One of the most potent threats to CFLs' superiority isn't their cost, but their contents. There's a small amount of toxic mercury in every one, which can be absorbed or inhaLed, potentially causing brain damage in adults, children and especially in fetuses. Fumble a CFL while changing a light, critics warn, and you unleash a poisonous fiend in your home. Throw it out and you're dumping mercury in landfills.

Those are both valid concerns, if sometimes a bit overblown. You should be careful when cleaning up a broken CFL, but don't go nuts — Snopes has debunked the myth that breaking one requires calling in an environmental cleanup crew. Keep kids and pets away, open the windows and resist the urge to vacuum, since that can kick up mercury vapor into the air; see the EPA's advice on cleaning up broken fluorescent lights for a complete guide. When they do eventually burn out, make sure to dispose of them properly.

Why do CFLs contain mercury?

Fluorescent and incandescent lights generally work the same way: They zap certain types of atoms with energy until their electrons freak out and release photons of light. Incandescent bulbs do this by shooting electricity into a thin metal filament surrounded by inert gas and encased in a glass shell. Metal normally emits invisible infrared light when heated like this, but get the atoms worked up enough and they'll produce a visible glow, too.

Metallic atoms are also the light source in fluorescent lamps, but they use vaporized mercury instead of a solid filament. The incoming electrical current is carried through a glass tube, straight or coiled, that's filled with mercury vapor and argon gas. The electrified mercury atoms begin vibrating and releasing invisible ultraviolet light, which in turn excites a fluorescent phosphor coating on the inside of the tube, finally producing the visible light.

(It's this jittery relationship, combined with a jumpy magnetic ballast providing electricity, that gives fluorescent lights their infamous flicker. Electronic ballasts don't have this problem.)

Mercury is a crucial part of how all fluorescent bulbs work, and replacing it is a daunting task. Still, manufacturers have cut back on how much they use — CFLs' mercury content dropped by at least 20 percent from 2007 to 2008. While the bulbs contained an average of 4 milligrams a few years ago, many now use as little as 0.4 mg. By comparison, mercury thermometers contain about 500 mg of mercury, and older nondigital thermostats contain about 3,000 mg.

Does mercury overshadow CFLs' benefits?

Fluorescent lights only release mercury when their glass breaks. Consider how often you shatter a light bulb while changing it, and divide that number by 10 — since a single CFL requires about that many fewer replacements — and that's your risk of mercury exposure.

An incandescent bulb doesn't contain mercury, but it still has a higher overall mercury footprint than a CFL, thanks to the coiled tube's renowned energy efficiency. Coal-fired power plants are humans' No. 1 source of mercury pollution, and energy-intensive incandescent bulbs require those plants to burn more coal than CFLs do. That extra coal burning releases far more mercury than even the combined amount inside a CFL and in the coal emissions needed to light it.

While most fluorescent lamps finish their lives without shattering, however, it's another story once they're thrown out. They can easy break in trash cans, Dumpsters or en route to a landfill. It's only a small amount of mercury, but it adds up as more and more people are buying them, and it also endangers sanitation workers who don't know they're carrying bags containing mercury vapor. All the more reason to read up on the EPA's guidelines for properly disposing of fluorescent lights.

Are incandescent bulbs burned out?

The main downside with traditional light bulbs is that they use only 10 percent of their energy to produce light, burning off the rest as heat. They've wasted 90 percent of the electricity people have been feeding them for the past 130 years — electricity that was mainly generated from coal and other fossil fuels. Congress put its foot down with the 2007 energy bill, introducing tougher efficiency rules that are expected to crush the market for incandescent bulbs beginning in 2012. Within a few years, the ever-cheaper CFL may dominate the Lighting market.

But don't count out Thomas Edison's original bright idea just yet. Despite the U.S. Department of Energy and EPA pushing CFLs, many people are still turned off by the light they emit, which is slightly bluer and more flickery than incandescents' warm, steady glow. To meet this lingering demand as well as the upcoming federal efficiency standards, several companies are scrambling to roll out a wave of next-generation incandescents. These bulbs keep their familiar shine and radiate less heat by reflecting some of the filament's light back inward. They're still more expensive than CFLs, but the price of such technology usually drops if it's successful.

Light(s) at the end of the tunnel

The future of artificial lighting is hazy, thanks to several recent technological and regulatory upheavals. Traditional light bulbs are almost certainly doomed once the new U.S. efficiency regulations take effect in 2012, leaving CFLs and improved incandescents to fill the void.

There's also a dark horse light bulb lurking in the shadows — light-emitting diodes, better-known as LEDs. These are already common in a variety of devices, ranging from the blinking red light on a video camera to the green power button on a computer. LEDs are more efficient, versatile and long-lasting than either incandescent or fluorescent lights, emitting light in a specific direction rather than radiating it outward indiscriminately, which wastes energy. They also absorb back what little heat they produce into an internal heat sink, leaving the LED itself cool to the touch.

While LEDs may seem like the obvious choice, they're still not entirely practical as a commercial substitute for incandescents or fluorescents. Several companies make bulbs that rely on diodes, but they aren't cheap. Odds are good the technology will eventually let LEDs overthrow their predecessors, but until then, the EPA and DOE are giving CFLs the green light.

SOURCE mnn.com

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