Quantum Dots Accidentally Replace Incandescent Lighting?

Lynne Kiesling

Last week Randall Parker had a neat post on LED lighting advances, and how much energy savings we could create by switching from incandescent to LED. The article he cites suggests that the switch would also save us $125 million/year in electricity costs. Randall wonders if that number is low, but I don’t think it is. Lighting doesn’t use as much electricity as you think, and if you take into account the technological changes to incandescent bulbs and the shift to compact florescent, I think that’s a reasonable estimate.

LED lighting is like the Post-It note in a lot of ways. It’s an innovation that is likely to have enormous implications, way beyond what we currently perceive.

LED lights give off lots of lumens in a very small package; in the KP household we’ve got several, for headlamps and bicycle lights. In the past couple of years the technology has advanced and been priced attractively. I bought the KP Spouse a fancy schmancy LED headlamp that has three level settings and a strobe setting, and it’s about the size of a pair of D cell batteries. His old headlamp made him look like a coal miner.

LED lights also don’t give off waste heat, because they do not emit light in the infrared spectrum (or at least I think that’s the reason). That’s another reason why they are so energy efficient; all of the energy input goes into producing lumens, not lumens+heat.

LED lighting is also like the Post-It note because of an interesting fact that Randall notes: the innovation he’s describing in his post, which is using quantum dots to create a coating that yields warm, yellow light from an LED, happened by accident. The researchers were exploring quantum dots for another application entirely, and it turns out to have this other nifty application. The history of technological change is littered with such accidental discoveries, many of which (like the Post-It note) have transformed our lives.


11 thoughts on “Quantum Dots Accidentally Replace Incandescent Lighting?

  1. Lynne,

    Some of my readers in the comments section of my post came up with details on how much electricity gets used for residential lighting. Look at the comments on that post. They suggest that the amount saved by phasing out incandescents would run into the billions of dollars per year.

    Also, think about it intuitively. At 10 cents per kwh you spend $1 for keeping a 100 watt bulb lit for 10 hours. How many hours do you burn 100 watt bulbs per year? 100? 1000? Multiply that by a few hundred million people. Hard to see how the savings from such a large amount of efficiency increase would be so small.

  2. Will it make a difference? I doubt it. Incentives make a difference, not technology.

    Miserable on the Job?: It Could Be the Lighting By Jared Sandberg From The Wall Street Journal Online June 11, 2004:

    George Tobia’s lighting epiphany came 13 years ago when, sitting in his office as the setting sun cast a rosy glow, it occurred to him to turn off the 12 fluorescent bulbs over his head. Suddenly awash in natural light, he said to himself, “This feels so good.” . . .
    The fax machine may be maddening and the computer may promote hostility, but no office gear can put you in a funk as quickly as fluorescent lighting. At best, it provides the light of a cloudy sky. At worst, it’s the source of physical maladies, and a creepy and synthetic downer. Far from the come-hither glow of candlelight, fluorescent bulbs cast a hell-and-back pall over everyone. . .
    Commercial builders love fluorescent lights because they’re so efficient. They run on about a quarter of the electricity that incandescent bulbs require, and they last roughly 10 times as long. The problem is, most office workers end up getting a lot more fluorescent light than they need, pretty much canceling out that efficiency. Many companies also leave their lights on all night long, probably because no one can find the switch. It’s an example of how corporations, as they attempt to maximize efficiency, often minimize it instead.
    “The lighting in most offices is much brighter than it needs to be, especially with computers,” producing glare and eyestrain, says James LaMotte, a professor of optometry at the Southern California College of Optometry.
    “People apply efficient lighting stupidly,” adds Naomi Miller, who runs her own design firm and formerly worked at Rensselaer Polytechnic Institute’s Lighting Research Center. “There are a heck of a lot of offices that are very badly lit.”

  3. LEDs do give off waste heat (that’s why they get warm when in use – and they’d need to be the unattainable 100% efficient to give off none), but they do produce far less of it than an incandescent lamp, per lumen of output and per watt of power used.

    Me, I’m looking forward to widespread LED headlights in cars.

  4. I should have looked more closely at the comments to the post, but my ad hoc speculation was based on what I know about residential lighting. Commercial lighting is another story, as Robert’s excerpt suggests. The luxury of having an office, not a cube in a farm, is that I don’t use my overhead florescents, but instead use compact florescents in table and floor lamps. Not exactly a rosy glow, but much better for my demeanor than the overheads, and about as efficient.

  5. I should have looked more closely at the comments to the post, but my ad hoc speculation was based on what I know about residential lighting. Commercial lighting is another story, as Robert’s excerpt suggests. The luxury of having an office, not a cube in a farm, is that I don’t use my overhead florescents, but instead use compact florescents in table and floor lamps. Not exactly a rosy glow, but much better for my demeanor than the overheads, and about as efficient.

  6. Current LED’s are ~25% efficient (i.e. light vs. heat), vs. 10% for incandescent, vs, 50-70% for Fluorescent lights). LED’s give off considerable heat, this is actually the main reason why high power LEDs have not been produced economically, i.e., the excess heat generated limits their max output and lifespan. The recent press release re: quantum dots uses a conventional blue LED, it just adds a new quantum dot based “phosphor”.

    Thus while LEDs are 2x more efficient than incandescent, we already have lighting available which is more 3-5x efficient. Compact fluorescent bulbs that fit in existing light sockets are available now, at much lower cost than LED lighting, and consume much less power than either incandescent bulbs or LED bulbs. So, no need to wait to save the world.

    Future LED lighting, particularly Organic LEDs, may be considerably more efficient, i.e. >75% efficient, and by combining separate LEDs for RGB colours will be able to be tuned to whatever colour balance and intensity is desired. That’s the real area of interest for next gen lighting.

    P.S.: However, for coloured light applications (eg. traffic lights, large video displays) LEDs are the most efficient technology and have very long lifespans), since either using incandescent, fluorescent or other backlight white light sources that are colour filtered by definition uses 90%)of available light.

  7. At 10 cents per kwh you spend $1 for keeping a 100 watt bulb lit for 10 hours.

    Ummm … no … a 100 watt bulb lit for 10 hours would be 1000 watt-hours or 1 kWh. Cost to operate would be 10 cents.

  8. At 10 cents per kwh you spend $1 for keeping a 100 watt bulb lit for 10 hours.

    Ummm … no … a 100 watt bulb lit for 10 hours would be 1000 watt-hours or 1 kWh. Cost to operate would be 10 cents.

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