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Xenophon · 08-29-2009, 11:09 PM

On the subject of CFLs, Mercury, color of light, etc., here are a few tid-bits you may find interesting.

Mercury: A CFL that complies with basic US standards contains about the same amount of mercury as one fish fillet (assuming ocean caught fish). A newer-design "very low mercury" CFL contains substantially less mercury than a single fish fillet. Standards in other countries may vary.
Light Color: CFLs are available in a variety of different "color temperatures." Think back to your High-school or college physics classes... The color of a beam of light can be described in terms of the temperature (really energy) of its photons (usually given in Kelvin). A standard incandescent bulb has a color temperature of 2700K. Daylight has a color temperature of roughly 6500K. The fluorescent bulbs found in offices are often either "warm white" (3400K) or "cool white" (4300K). Finally, there are also "full spectrum" bulbs, which put out light across much of the visible spectrum -- they have peaks at 6500K and at 2-4 other temperatures. When well made, a "full spectrum" bulb really looks like sunlight. The point of all this is that you can purchase CFL bulbs in just about any color temperature you like. Just not at your usual grocery store or big box store. In the US, visit www.1000bulbs.com. In other countries, I have no idea.
Dimming: Dimmable CFLs have been available for a long time, but were difficult to find. Now they are both easier to find and far less expensive than previously. Prices have fallen to around 2x the cost of a non-dimmable CFL. Still way cheaper than incandescent.
Quick start: Any reasonable CFL should be "instant-on." What this really means is that it should reach 50% light output in the first 1/2 second after you turn it on; 100% light output may take up to several minutes. Cheap, non-brand-name CFLs often fail this particular test.
Size: Available CFLs can be smaller than incandescent bulbs with comparable light output. You may have to look around a bit, however.

When I last looked at LED vs. CFL lighting (about this time last year), the available units produced similar lumens/Watt. Thus, if you want 1600 lumens you need a 23-Watt unit. And that's going to produce about 22.9 Watts worth of heat -- no difference whether it's LED or CFL. Thus the heat-sinks someone mentioned up-thread. Of course, LEDs really are "instant-on" at full light output -- a nice advantage.

The big deal, however, is that LEDs are quite early in their technology curve -- there's a long way to go before we reach theoretical peak efficiency. By comparison, CFLs are a mature technology where the engineers have already squeezed out most of the available efficiency gains. So somewhere down the road (hopefully not too far) we should start to see LEDs that are much more efficient than the CFLs we'll be replacing. And that'll be great!

Xenophon

08-29-2009, 11:09 PM	#45
Xenophon curmudgeon Posts: 1,487 Karma: 5748190 Join Date: Jun 2006 Location: Redwood City, CA USA Device: Kobo Aura HD, (ex)nook, (ex)PRS-700, (ex)PRS-500	On the subject of CFLs, Mercury, color of light, etc., here are a few tid-bits you may find interesting. Mercury: A CFL that complies with basic US standards contains about the same amount of mercury as one fish fillet (assuming ocean caught fish). A newer-design "very low mercury" CFL contains substantially less mercury than a single fish fillet. Standards in other countries may vary. Light Color: CFLs are available in a variety of different "color temperatures." Think back to your High-school or college physics classes... The color of a beam of light can be described in terms of the temperature (really energy) of its photons (usually given in Kelvin). A standard incandescent bulb has a color temperature of 2700K. Daylight has a color temperature of roughly 6500K. The fluorescent bulbs found in offices are often either "warm white" (3400K) or "cool white" (4300K). Finally, there are also "full spectrum" bulbs, which put out light across much of the visible spectrum -- they have peaks at 6500K and at 2-4 other temperatures. When well made, a "full spectrum" bulb really looks like sunlight. The point of all this is that you can purchase CFL bulbs in just about any color temperature you like. Just not at your usual grocery store or big box store. In the US, visit www.1000bulbs.com. In other countries, I have no idea. Dimming: Dimmable CFLs have been available for a long time, but were difficult to find. Now they are both easier to find and far less expensive than previously. Prices have fallen to around 2x the cost of a non-dimmable CFL. Still way cheaper than incandescent. Quick start: Any reasonable CFL should be "instant-on." What this really means is that it should reach 50% light output in the first 1/2 second after you turn it on; 100% light output may take up to several minutes. Cheap, non-brand-name CFLs often fail this particular test. Size: Available CFLs can be smaller than incandescent bulbs with comparable light output. You may have to look around a bit, however. When I last looked at LED vs. CFL lighting (about this time last year), the available units produced similar lumens/Watt. Thus, if you want 1600 lumens you need a 23-Watt unit. And that's going to produce about 22.9 Watts worth of heat -- no difference whether it's LED or CFL. Thus the heat-sinks someone mentioned up-thread. Of course, LEDs really are "instant-on" at full light output -- a nice advantage. The big deal, however, is that LEDs are quite early in their technology curve -- there's a long way to go before we reach theoretical peak efficiency. By comparison, CFLs are a mature technology where the engineers have already squeezed out most of the available efficiency gains. So somewhere down the road (hopefully not too far) we should start to see LEDs that are much more efficient than the CFLs we'll be replacing. And that'll be great! Xenophon