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A better kind of lightbulb?

The views expressed are those of the author and are not necessarily those of Scientific American.

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vu1 r30 light bulbThis week, the lighting start-up company vu1 is beginning to ship a new type of lightbulb that could displace compact fluorescents and LED lamps as the energy-saving bulb of choice. The technology, known as cathodoluminescence or electron-stimulated luminescence (ESL), offers similar energy savings, but provides a more natural quality of light.

My life in the past several years has been a living lightbulb joke. I’ve changed, re-changed and re-re-changed the bulbs in my house trying to find replacements that save money but don’t make our skin look like zombie flesh. Compact fluorescents and LED lamps save energy, last longer, and emit less heat than incandescent bulbs. But their light is ickier, versions advertised as "dimmable" often dim only over a limited range, and CFLs take maddeningly long to come to full brightness. No single type works everywhere. LEDs are great for desk lamps, but their narrow beams fail to fill larger spaces. In darkly painted rooms, I went with cold-cathode fluorescents with a low brightness temperature. I’ve filled a big box in the basement with all the bulbs I’ve tried and rejected. So much for saving money.

Spectrum of CFL, LED, incandescent lampsThe color quality has to do with how these bulbs work. The white(ish) light you see is given off by a phosphor coating. In a CFL, the phosphor glows when backlit by ultraviolet light from mercury vapor; in an LED bulb, it soaks up light from a pure-blue LED. (The mercury is why you can’t just throw a CFL in the trash when it dies.) On the left is a graph showing the spectra of incandescent, CFL, and LED bulbs; the x-axis is the wavelength in nanometers. Although this particular graph was provided to me by vu1, which has a certain self-interest in showing its competitors in their worst light, it matches information from other sources such as the lighting control company Lutron and the RPI Lighting Research Center. The CFL spectrum is a series of spikes, reflecting the combination of phosphors used to approximate white light; CFLs therefore accent certain colors and fail to render others.

LED bulbs, which use a different type of phosphor, have a smoother spectrum, but the blue LED that drives the phosphor creates a sharp peak in the blue, short-wavelength range of the spectrum, which might pose a "blue light hazard." Ignacio Provencio of the University of Virginia will have an article in our May issue about how our eyes have a special class of photoreceptor that doesn’t form images; instead it absorbs blue light to synchronize our body clock with the day/night cycle. Too much blue light could disrupt your sleep cycle. I’ve also seen claims that excessive blue light might fry your retina and increase your chances of developing macular degeneration. The French counterpart to OSHA issued a report last November warning that children are at particular risk, although Physics World quoted other experts who thought the claims overblown.

The new ESL bulbs use a phosphor, too, but one that does not absorb light at all—instead, it absorbs electrons. Roughly speaking, ESLs are cathode-ray tubes repurposed as lamps. The electrons stream off a metal cathode plate and are pulled by an electric field toward an anode, a thin layer of metal on the backside of the phosphor. Charles Hunt of University of California at Davis, who helped to develop the phosphor, explained to me that ESLs differ from the CRTs used in old TV sets by virtue of their lower electron densities and energies.

Spectrum of ESL, incandescent lampsBecause they use a different phosphor, ESLs provide a somewhat more natural light; see the spectrum at left. The company claims all sorts of other advantages, too: the bulb turns on faster, shines omnidirectionally rather than in a narrow beam, dims over a wider range, and contains no mercury. I’ve been trying out a demo, an R30 spotlight for a recessed fixture in my kitchen. When you flip the switch, it comes to full brightnesss in a second or two. My wife judges the light to be yellower and milder than a CFL’s. Measured with a Kill-a-Watt, the bulb draws 16 watts, about as much power as a CFL of the same brightness, roughly equivalent to a 60-watt incandescent. I’m able to dim it down to, or up from, 20 percent of maximum brightness. The main downside is that the bulb is much heavier than any other I’ve ever tried—nearly a pound.

Since vu1 first announced the bulbs last year, people on Internet discussion groups have worried about x-ray emission, since the technology is similar to that of an x-ray tube. Hunt said ESLs do produce some x-rays, but at levels below the ambient background dose. The company says that UL-certification included x-ray safety testing.

The R30 begins shipping this week, for $20. The company says it’ll introduce an A19 standard bulb shape in the summer, followed by decorative and vanity lighting.

Image and graphs courtesy of vu1

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  1. 1. DiscomBob 9:16 am 03/21/2011

    Expected life?

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  2. 2. RDH 9:41 am 03/21/2011

    CFLs can’t be thrown in the trash? Oh yes they can and they are all the time. Just pick one up, walk over to the can and let go over the can. Gravity does the rest.

    If the greenies really think people are not tossing these things in the trash the greenies really are totally disconnected from reality.

    Soon landfills all over the U.S. will be leaching mercury from millions of CFLs.

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  3. 3. candide 12:06 pm 03/21/2011

    "versions advertised as "dimmable" in fact dim only over a limited range"

    Why can’t SciAm get the facts right? LED’s are dimmable over their whole range. The PROBLEM is that older dimmers are optimized 60-100 watts, and most LED’s bulbs are 3-10 watts. Newer dimmers work fine with LED bulbs – I have several that are used daily.

    One difference, thst I do not mind at all, is that the LED light color does not change over the dimm range. Incadescents would get progressively "yellower" than the 2750K temp as they are dimmed, LED’s "hold" their color.

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  4. 4. okwhen 12:09 pm 03/21/2011

    The first part of your comment is absolutely correct. However, after your words of revelations it might be conceived to some that you are mocking conservationist a.k.a greenies. Please clarify, this is a scientific site where meaning and facts are some of the key elements.

    Conservationist are quite aware of peoples actions and are quite hindered with propagandist statements. Corporations are the problem by controlling the government. All that is needed to completely alleviate the problem is a deposit at the time of purchase. The same is true for rechargeable batteries, plastic bottles, etc. Many environmental issues have relatively easy solutions however, for some reason corporations / government fight them at every turn.

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  5. 5. candide 12:13 pm 03/21/2011

    Great article – no color temps, broken links, and inaccurate "facts."

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  6. 6. gmusser 12:32 pm 03/21/2011

    I do have new dimmers, and what I report about dimmability is from my direct experience with a variety of LED bulbs. Based on what you write, though, I’ll correct the text to indicate that my experience is not universal.

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  7. 7. gmusser 12:34 pm 03/21/2011

    I guess I should be flattered that you hold me to such high standards! I’ve fixed the two broken links.

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  8. 8. candide 1:26 pm 03/21/2011

    I am all for energy conservation. I look forward to new lighting (bulbs and more, like OLED).

    But I find articles like this to be very biased (in favor of the particular lights mentioned), lacking facts (like color temps, lumens and other measurable items).

    This article mentions that the author "heard" that blue light can interrupt sleep cycles. What temp and brightness og blue light? Where was that "heard" ? In legal terms this is hearsay and is unreliable.

    I am naturally suspicious and suspect that the author may have some connection, direct or indirect, to the manufacturer of ESL bulbs.

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  9. 9. candide 1:46 pm 03/21/2011

    For example, CREE LR6 LED ceiling fixtures dimm very well, down to about 12% of their output. Philips Ambient LED A19 also dimms very well, to 10% or less of its full output.

    I use both Lutron S600 and various Insteon dimmers with these bulbs (and some dimmable CFL and CCFL bulbs), without issue.

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  10. 10. gmusser 4:23 pm 03/21/2011

    I said I’d seen (not "heard") claims to this effect and I provided the links. I simply wanted to flag the issue for readers to pursue on their own. I don’t claim to have investigated this question thoroughly, and I have no connection, financial or otherwise, to this company. I’m just a homeowner looking for energy-saving technology and sharing what I find out with readers of this blog.

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  11. 11. lamorpa 8:48 am 03/22/2011

    Bulb life is an essential piece of information to the point that without it the analysis is pretty much irrelevant. If the bulb lasts 5-10 years, it could be green. If it last 2 years, it is very possible the total resource and energy load is greater than incandescents. Like most current ‘green’ products today, it is, sadly, a toy for the rich. (the big toy being, of cource, personal solar PV)

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  12. 12. tharter 9:22 am 03/22/2011

    Yes, but no good deed goes unpunished, eh George?

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  13. 13. NedC 12:42 pm 03/22/2011

    Reading about your experience makes me very glad that I’m as indifferent to colour as I am;) The odd thing is that I am an artist, but though I’m not colour blind I work almost exclusively in black and white media have little interest in colour. I started converting to CFLs ages ago and they’ve always seemed just fine and I appreciate the lower bills.

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  14. 14. xxfallacyxx 12:43 pm 03/22/2011

    "All that is needed to completely alleviate the problem is a deposit at the time of purchase."

    I’m getting the sense that you’re an idealist. I suppose having a deposit on aluminum cans has completely solved them being thrown into the trash all over the country.

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  15. 15. gmusser 10:19 am 03/23/2011

    The company claims a lifetime of 10,000 hours, similar to that of CFLs.

    Link to this
  16. 16. bucketofsquid 5:55 pm 03/23/2011

    10,000 hours is a bit over a year of continual use. I have yet to have any lightbulb get close to that. I’ve switched from incandescent to CFL which seem to last longer but even they don’t get close to a year of normal use. Haven’t found LED lights available in my area.

    As for these lights; my light fixtures are almost all over 70 years old. I doubt they could take the weight.

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  17. 17. Brian H 7:03 pm 03/23/2011

    The X-rays are a feature, not a bug. See the hormesis phenomenon: stimulation of cell repair mechanisms.

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  18. 18. r_jean 10:53 pm 04/6/2011

    Thanks for continuing to share your experiences. It makes interesting reading and you do a good job of providing sufficient information for follow-up by the interested reader. Some folks are obviously frustrated that you are not a different person writing a different sort of blog. It is cheering to see that they are so hungry for the information, though, as well as willing to share their own info.
    Anyway, great blog!

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  19. 19. Momus 10:44 pm 04/12/2011

    Is there no concern about that sharp spike in ESL spectrum?
    Or will they be build to filter this out?

    Link to this
  20. 20. hankroberts 1:28 pm 05/10/2011

    > X-rays

    So, if I put one of these on say 220v instead of 110, does the X-ray emission go up significantly? How about pulsing it with a capacitor for brief higher voltages?

    I recall sometime early in the 20th Century reading instructions for attaching the high voltage from an old Model-T spark coil to a vacuum tube that has the silvery "getter" film on the inside of the glass — creating a homemade X-ray source. I think it was SciAm’s "Amateur Scientist" column.

    My dad talked me out of it at the time.

    Kids, don’t try this at home …..

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  21. 21. hankroberts 1:29 pm 05/10/2011

    Blue light (link only good for about a week for nonsubscribers):

    Link to this
  22. 22. willscarletnss 8:25 am 07/20/2011

    An LED lamp (LED light bulb) is a solid-state lamp that uses light-emitting diodes (LEDs) as the source of light. The LEDs involved may be conventional semiconductor light-emitting diodes, to organic LEDs (OLED), or polymer light-emitting diodes (PLED) devices, although PLED technologies are not currently commercially available.


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