Design Article
CFL and LED lamps: White light in a 'green' world
David Carey. Portelligent
10/6/2008 12:01 AM EDT
The fluorescent bulb is substantially more efficient than the incandescent alternative, producing greater direct light (and less heat) per input watt. Though long used in offices and other commercial and residential settings, fluorescent lamps didn't come in forms suitable for small-lamp replacement until the 1980s. The past couple of decades have seen miniaturized screw-in CFL bulbs finally achieve quite low price points, promoting consumer adoption.
The MaxLite bulb examined here is a 20-W lamp claimed to produce equivalent illumination to a 75-W incandescent. Like all of its traditional fluorescent peers, the MaxLite CFL uses a glass tube whose phosphor lining emits from UV radiation produced by ionized gas in the tube. The CFLs achieve miniaturization through both a smaller tube diameter and through folded or spiral-wound construction. The CFL ballast used to light the tube also must be stuffed into the space constraints of a standard screw-in lamp. To do this the MaxLite, and its competitors, use a downsized supply to create a suitable lamp drive in relatively little space.
A pair of transistors, quartet of diodes, and collection of capacitors and inductors all come together to first rectify the AC power and create a follower resonant inverter circuit that generates the high-frequency, high-voltage power used to fire the lamp. I'm no power supply expert so I may have the precise topology wrong, but both inspection of the minimal components and finished goods' price points show that the CFL ballast can be made inexpensively.
The phosphor-coated glass tube has its own evolved history in manufacturing such that the combination of lamp and electronic drive circuits can now be brought to market at prices that start to rival the (relatively) short-lived incandescent alternative. When efficiencies and lifetimes are considered, the CFL begins to look attractive not only for its "green" attributes but also for total cost of ownership.
Wearout of lamp phosphors remains an issue, and vent holes in the lamp-base enclosure suggest that heat-related wearout of ballast electronics might be a factor. Still, the lifetime of quality CFLs can run to many months or even years.
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r3son8tr
10/15/2008 3:31 PM EDT
I switched over most of my household lamp fixtures to CFL about a years ago. The only fixtures I cannot change over are the two that are controlled by dimmers - you can't yet do that with a CFL. I've even got CFLs in two of my ceiling fan fixtures (the ones that don't have a dimmer control) and one yellow "bug light" CFL outside on my front porch.
While it's true that CFLs take time to warm up to full brightness, I haven't noticed that it is a problem that negatively affects our lifestyle. They are certainly bright enough initially to provide useful light, and they are at full brightness after just a few seconds.
The color temperature is also quite good. I have not noticed any of the "harshness" or "coldness" that some people claim to see with CFLs. The lamps I've been buying seem quite warm to me. The cost has come down significantly, so I can buy a four-pack for about 9 bucks, and I haven't had to replace any of my CFLs in the year or so that they've been in service. So far so good.
My main concern with CFLs is environmental. While I know that they must be recycled - and I've seen recycling bins at Home Depot - I'm not entirely convinced that the general public understands that they cannot be put in the trash. With standard tube florescents, it's difficult to just throw them away due to their size, but CFLs are so small, people may just naturally toss them in the garbage.
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Thermionic
10/17/2008 4:45 AM EDT
Heatsink may be required for LED lamp because of the relatively small surface area of the light source, and its integration into the base. Original article seems to assume that most inefficiency arises from the power supply, which is not true. The heatsink helps to disipate heat conducted from the LEDs. The CFL source has a large area, poor conductivity, and is largely remote from the base housing.
In addition, LEDs may fall in efficiency, or fail, if overheated. Original article appears to assume that both types of fitting should be cooled to a similar temperature, but this may not be the case.
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thormj
11/13/2008 10:34 AM EST
What you are looking for is a high CRI (color rendering index). Most CFLs are abysmal at around 80 -- this a shade better than the original F40 cool-white bulbs.
But, you can do better; there are some good CFLs out there, at a cost ($15 or so each; look at the photography magazines or google for High CRI CFL).
You can get tube fluourescents with high CRIs as well (Phillips TL950 98 CRI) -- and it makes an incredible difference. I just wish HD and Lowes would quit with "sun-like" and "cool white" and post CRI numbers.
I haven't seen a CRI on LEDs yet, so I'm assuming they're embarassed about it.
Exception: GELcore LED's are UV and use the same rare-eath phospors as tubes do, so they have a line of High CRI LEDs.
-Thor Johnson
http://www.scientificconservation.com
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dave-o
11/13/2008 3:50 PM EST
I have no experience with LED lighting, but over the last 10 years, I have slowly replaced most of my incandescents with compact fluorescents. Way back then, the colors were so bad that we only put them where the color didn't matter: the front hall, the garage, etc. Otherwise, my wife would complain that our skin looked yellow, or the carpet looked "sick" (under the CFLs of the time, it did!).
But this year we've replaced most of the incandescents in the family room, hall, laundry room, kitchen and other high-use areas with with CFL, with no complaints. All the reading lights are CFL (get the higher wattage bulbs to have enough light). The prices are low, and you can choose the light color (temperature) you want. The prices are very low at Home Depot and elsewhere.
I'm to the point where I buy a 4-pack of CFLs to get two that I need, then I go around the house hunting for other incandescents to replace. As of last weekend, all the fixtures I opened already had CFL. This is a testament to the CFL's color quality-I was unaware that they weren't incandescent.
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Gods
1/14/2009 3:11 AM EST
Anybody know this company? I got email from them with some products, please check below:
We are professional LED lamp manufacturer in China, and our main products are Li-ion battery, miner's caplamp, spotlamp, LED Bulbs, LED Strips, LED Spotlight and etc.
Our product features: Free maintain, long time usage, light weight, waterproof.
For more information or any requirement, please feel free to contact us.
Best Regards
Mr. Jeff
Win Create Holdings Co., Ltd.
Tel: 86-755-61220808
Fax: 86-755-61220801
Email: jeff@happywong.com
Msn: ledfactory@hotmail.com
http://new-wisdom.spaces.live.com
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Gods
1/14/2009 3:12 AM EST
Anybody know this company? I got email from them with some products, please check below:
We are professional LED lamp manufacturer in China, and our main products are Li-ion battery, miner's caplamp, spotlamp, LED Bulbs, LED Strips, LED Spotlight and etc.
Our product features: Free maintain, long time usage, light weight, waterproof.
For more information or any requirement, please feel free to contact us.
Best Regards
Mr. Jeff
Win Create Holdings Co., Ltd.
Tel: 86-755-61220808
Fax: 86-755-61220801
Email: jeff@happywong.com
Msn: ledfactory@hotmail.com
http://new-wisdom.spaces.live.com
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Etmax
8/2/2009 7:41 PM EDT
LED's have to be kept cool to maintain their efficiency, that is why the heatsink is so large. Where as 100degC may seem ok for a power semi, LED's should be operated at <50.
I often wonder if the carbon cost of manufacture is taken into the equation when stating CFL's and LED's are greener.
Lastly someone has developed a nano scale treatment that makes incandescents >20% efficient. Maybe there will be a comeback ??
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