The End Of The Light Bulb?

sdmonroe wrote to mention an MSNBC article discussing the likely eventual replacement of common light bulbs by LEDs. That replacement is likely to come quicker thanks to an accidental discovery announced this week. From the article: "Michael Bowers, a graduate student at Vanderbilt University, was just trying to make really small quantum dots, which are crystals generally only a few nanometers big. ... When you shine a light on quantum dots or apply electricity to them, they react by producing their own light, normally a bright, vibrant color. But when Bowers shined a laser on his batch of dots, something unexpected happened. 'I was surprised when a white glow covered the table,' Bowers said. 'The quantum dots were supposed to emit blue light, but instead they were giving off a beautiful white glow.'"

LED lights

[totallygeek]

I have been impressed with the LED lights over florescent or incandescent. The subdued lighting is fine with me and the energy consumption / bulb longevity is the best part. When my wife and I move (build a house), we will go 100% LED.

leds

[jsmucker]

I will go to leds when they meet my budget....just a matter of time.

Not sure this discovery is necessary

[gvc]

White LEDs are already 3 times as efficient as mercury fluorescent, and fluorescent tubes are 3 times as efficient as incandescent. They (fluorscent and LEDs) can get pretty good colour accuracy, too, if they want to. The only thing holding them back is price. I'm not sure what this new invention might bring to the table in that regard.

No Effing Way!!!

[Anonymous Coward]

Have you ever tried an LED light? They suck!!! They do not cast nearly enough light. The light color is a disturbing and unnatural color, usually with too much blue in it.

Florescent tubes are FAR superior to LED lights and yet so many people prefer good old incandescent lights to even florescent tubes. Hell, even something as simple as a flash light. Try an LED flash light and then try a xenon Mag Light and tell me which one rocks your socks.

LED lighting is one of those technology "revolutions" that are for the sake of technology. They are NOT better.

well, likely not.

[way2trivial]

at my workplace, a hotel on the beach.

We had for many years yellow colored standard bulbs, as they don't attract bugs.

we started replacement with yello fluro twist bulbs, to save on electricity and replacement costs.

in research, it turns out, we can use white fluro-- as they only emit light in a very narrow spectrum of white light, unlike an ordinary filament bulb.. and the range they do emit light on, suitable for humans, does not attract bugs.

I'd guess these low power led lights also emit white light on a very narrow band....

Spelunkers Joy

[joey_knisch]

About 7 Years ago I brought a LED Headlamp to a spelunker convention. They were leery at first but when I didn't change my batteries once during the entire weekend they were sold. The next year there were about 10/50 of us on LED. Now everyone has an LED lamp.

Costly Quantum Dots

[ObligatoryUserName]

If the manufacturing breakthough talked about in this article [monstersandcritics.com] pans out, the cost of Quantum Dot manufacture will drop from $2,000 to $400 per gram. That's huge improvement, but I still wouldn't expect to see Quantum Dot lightbulbs on ThinkGeek anytime soon...

Just a few disadvantages of LEDs

[Anonymous Coward]

Disadvantages include:

Low candle power. LED lights are lacking in their production of, well, light.
Unnatural color. LED lights have unnatural and sometimes disturbing colors. Incandescent lights have a warm glow that is closer to natural light and "full spectrum" incandescents produce something very near sun light.
Expense! Producing an LED "bulb" with the same candle power as an incandescent bulb is FAR more expensive than the incandescent.
Possible health issues due to the poor light quality. A plant will grow under incandescent light, it will not grow under an LED.

led's, worse than flourescents.

[plasmacutter]

I have an led flashlight.

led's emit a very cold light. Fourescent light is described as cold and "vitamin burning", but led light is even worse in this respect.

It works for headlights, emergency beacons, and select areas, but generalized room lighting is not one of those areas.

Re:It's about damn time!

[DrLex]

Actually LEDs do produce heat, albeit the ratio of heat/light is much lower than with incandescent bulbs. The common LED is designed for a maximum current of 20 ~ 30mA, and at these currents the heat production is negligible. You can drive them at a higher current, but then the heat production becomes significant and can cause the LED to burn out (and at real high currents, the junction simply breaks down immediately). The more performant Luxeon LEDs are attached to a tiny heatsink and the high power ones (3W and 5W) require an additional heatsink to use them beyond 1W.

Still a way to go yet.

[crawdad62]

I'm a professional firefighter and a lot of the guys have started using LED flashlights. I had just purchased my own (out of my pocket and not the city's) rechargeable StreamLight that uses a halogen bulb. When I started seeing the LED's showing up I thought I had made a mistake. They "seem" bright but after seeing them more and more I'm convinced it's just because the light is so white (slightly blueish) and clean.

However even though it looks brighter in fact it's less so and seems to accentuate shadows MUCH more.

I really haven't discussed power consumption with anyone yet but for now........ at least in this application....... I'll stick with the older technology.

LED disadvantages

[Temeraire]

Anyone who tries (like me) to build small lighting devices with LEDs rapidly discovers lots of practical difficulties. To equal the light output of one cheapo fluorescent tube you need hundreds of the little blighters. It is not easy to make their output look even, rather than dotty. And with that large number, reliability is a real problem. Even a 1% failure rate (amplified to 3% or 5% by the LEDs often being in series) rapidly translates into major unevenness. Even production lines struggle to make large arrays of LEDs stay 100% alight, but little people often get sold the bin ends, which fail rapidly in service.
      Also LEDs are NOT yet more efficient than fluorescents. Their data sheets never give the one number that really matters: what percentage of input energy actually emerges as light? The answer is usually frighteningly low. Therefore LED devices tend to cook themselves to death if run really bright.
      To run LEDs stably requires either a wasteful series resistor or an expensive semiconductor constant-current device. And cheap low-voltage power supplies are actually badly life-limited by their electrolytic capacitors. In my experience many LEDs die prematurely because of a failing power supply and hot sunshine.
      Don't get me wrong. LEDs are the future, but you must be wary of calling them energy-saving, long-lasting, or easy to use!

"LEDs don't emit heat"

[Tau Zero]

I wonder how many people are going to read this in the article and assume that LEDs are not just more efficient than other types of lamp, but 100% efficient?

(I hate scientifically-illiterate journalists.)

Re:It's about damn time!

[Hedon]

When I was finishing up my PhD (on InfraRed LED's) about 5 years ago, HP was making high-efficiency Red LED's with 50% light output efficiency. At the same time commercially available blue (GaN) LED's were only 10% efficient. Green LED's were somewhere inbetween.

I should really google for the state-of-the art visible LED efficiency, but am hoping for someone to post a more informative post following this one.

Re:Current LEDs are not there yet

[tylernt]

Were they placed horizontal or base-up? When CFs are installed base-up, the heat from the bulb rises and tends to cook the ballast, shortening lifetime. They do a lot better in base-down or horizontal installations.

I have a huge 45w (200w equivalent) CF in my garage. Going on 3 years, still works great. And it's even base-up.

I've had a few CFs burn out within a few months, too. I think some of them just have manufacturing defects.

Mixed reviews from me

[Just Some Guy]

I've switched a lot of my bulbs over to the CFs available at my local home store (Feit Electric; their websites down right now or I'd link it). The problems I have with them:

1. Most of them start nearly instantly, but dimly. They get brighter as they go, usually peaking after a minute or so.
2. At least half of them smell like magic smoke when you get close to them. One of them had me looking for an electrical fire inside my walls until I figured it out.

Once they're up and running, they're bright, nicely colored, and cool to the touch. But having to wait a full minute for the stairwell bulb to get bright is pretty suboptimal.

Are these "features" of all CF bulbs, or is the brand I've been buying really crummy?

Re:LED efficiency versus Compact Fluorescents

[dr_db]

CFL's do not like enclosed fixtures - I live in a rental, so I am not inclined to change them, but *every* cfl I put in those fixtures failed. I did post-mortens on them, some seemed to have unsoldered themselves (wires off the board) and others just seemed to have died. They never seemed to feel hot enough to melt solder, but the conditions in the base while running might have been pretty rough. So 15 have failed, 2 survived (in open socket applications). Many rooms in my house have regular tube fluorescents, which rarely give me trouble.

Re:Not sure this discovery is necessary

[fossa]

Bulb Efficiency (lumens per watt)

• Incandescent: 14-17.5 [1]
• White LED: 29-37.5 [1]
• Fluorescent: 50-100 [2]

[1] Why LEDs can be 10 times as efficient as incandescents in some applications but not in general home lighting! [misty.com]
[2] Are fluorescent bulbs really more efficient than normal light bulbs? [howstuffworks.com]

I'm a bit surprised at those fluorescent numbers... I don't have the box to one of my fluorescent bulbs handy to double check that, but I do know that while not as hot as incandescents, they become very hot to the touch when in use. I've never touched a lamp sized LED bulb however.

One disadvantage of fluorescents is that they contain mercury. Newer fluorescents may have found a way around this however; I'm not sure.

Not surprisingly, many of the websites I saw talked about future improvements in LED tech with goals around 100 lumens per watt.

AC vs DC

[MDMurphy]

AC has it's advantages, especially for long distance transmission. But in a house, it's gradually losing out. If you don't count lightbulbs, I'd say I have more DC things plugged in than AC. So many of the outlets are connected to "bricks" or "wall warts" to change the high voltage AC to low voltage DC. Things that don't have an exterior brick, like the DVD player or TiVo just do the conversion internally. While the higher voltage AC might have some benefits of lower loss in the wires, I'd think that umpteen separate transformers and rectifiers are negating a large percentage of that benefit.

If lighting were go to DC, then a re-think of the home wiring would really be in order. If there were a "standard" DC voltage and current available to lower power devices, we might not have wall transformers with anything from 3v-12v hanging off our surge supressors.

So in-house DC makes lots of sense. Send the AC to things like ovens and clothes dryers, and DC to most everything else.

This is awesome!

[Dr. Spork]

The frequency distribution of this light is so much more natural than the other low-energy alternatives! I wonder if it could be made to match the frequency distribution of sunlight more closely by just rearranging the mixture of the sizes of the quantum dots. Anyway, this is excellent news. It's because of the spectrum distribution of fluorescent bulbs that I refuse to use them. It's not that I like wasting energy, but even without ugly light, winter is depressing enough in upstate New York!

Re:Not sure this discovery is necessary

[westlake]

I imagine a hundred years ago the fact that incandescent bulb gave 2800K to candle's 1200K really hindered its adoption. Because candles were what people came to expect.

The mid 19th Century was home was lit by natural gas (if you could afford it) or by kerosene and other petroleum based lamp oils (dangerous).

Think for a moment how fifty to seventy-five years of experience with gas illumination affects interior design, men and women's fashions, cosmetics, etc.

There were real barriers to change, Competition to Edison's Lamp [si.edu]

Re:A return to white street light

[DJDutcher]

There is another advantage to the yellow orange high preasure sodium lights. They aren't as big of a problem when it comes to light polution, because it is easier to filter their narrow spectrum. That makes astronomers happy because they can put fitlers on their telescopes. A lot of dark sky advocates will ask people to switch to high preasure sodium, if they have to have a light.

I know what you mean though. I do hate the way they look. The orange glow even makes trees look creepy.

Re:LED lights

[shawb]

My guess: What is more likely to happen is these microdots could just replace or augment the fluorescent material in typical flurescent bulbs, with appropriate re-engineering. Although as an LED coating this would be amenable to more portable light, such as the little LED keychain lights except with a more natural looking spectrum.

After a little research, it appears that LEDs have been designed that surpass the efficiency of compact fluoros, but these are not on the market yet. More info on on Wikipedia [wikipedia.org]. However, this efficiency is for a given pure color LED, and the flourescence required to make an LED emit white light will reduce the efficiency somewhat. It would be interesting to see what the efficiency of fluorescence is with these microdots vs more traditional materials, in addition to differences in manufacturing costs and health/environmental factors.

So it will break down to we have a new tool which will be better in some circumstances. The pros and cons of will have to be weighed out in each situation. Where shock resistance and length of life is important, LEDs can have a significangt advantage over fluorescent bulbs.

Re:A return to white street light

[thomasa]

I disagree with your like. I find the white lights to be over
bright and obnoxious. I much prefer the muted look of the
sodium vapor lights. Especially from the air. The yellow
lights are much more pleasant to view. What would be really
nice is if we could change them to our liking. I have one
of those bright white lights in the street outside my house.
If it had knobs on it where I could change its spectrum, that
would be cool. My ex-wife's neightborhood has no street
lights at all - which I really prefer.

Re:Not sure this discovery is necessary

[Anonymous Coward]

It probably wasn't the flash, but inadequate UV filtering on the optical path. The sensors (CCD, etc) in digital cameras tend to pick up UV a little too well, and it gets stored in the image as light intensity.

For women, this becomes a problem, because almost all cosmetics sold reflect UV pretty well, especially foundation. The end result is, that a digital camera with poor UV filtering, taking a photograph of a woman wearing foundation, more often than not results in the woman's face and upper neck looking brighter than the rest of her skin.

Re:LED lights

[Anonymous Coward]

Thanks for the extra info - I was just going from the article :)

Looks like they could be a good move, as long as they become as easy to make as fluorescents.

I guess the environmental cost of making the lights should be taken into account as well, along with recycling possibilities. Hopefully, LEDs will stack up well there as well!

Re:AC vs DC

[MDMurphy]

I do understand, and I can read. It would be idiotic to suggest that the world start distrubuting DC, so I mentioned that AC is appropriate for that. Nor did I suggest a house running entirely on DC. Feel free to read my post again.

To repeat, and I'll type slowly this time, a large number of devices in a house today run on low voltage DC. If you don't count the light bulbs then I'd venture a guess that most of the electrical devices in a house today are low voltage DC. Since the orginal article suggested LED lighting, which is generally low voltage DC, then the majority of devices in a house then would be low voltage DC.

Since traditional houses are currently wired for higher voltage AC, this means many, many small transformers and rectifiers at each item: PCs, VCRs, Clocks, radios, cell phone chargers.. Most of these use different voltages and have different current requirements. While a large house wired for DC might have greater losses in-house than AC, the inefficiency of dozens of transformers and rectifiers aren't terribly efficient. The comparison I made about lossed in the many transformers was when comparing them to a single, or fewer, DC sources in a house.
While the original LED discussion spun many posts about heat, every brick and wall-wart that's running hot is also generating heat that is not part of an efficient energy transfer. A standard low voltage, low current, DC distribution in a house could have greater efficiencies. Running a DC clothes drier on on wires 100ft long would not be an example of a low voltage, low current application. But a cell phone charger or clock radio, or any of dozens of LED lamps would be.

AC equipment in the US is expected to work on 120v 60hz. Because that's available, that's what's built. If 5, 12, or 40 VDC was what was available in any house, that's what these low power devices would connect to. If there's a common source and connector, hardware will pop up to use it. The hundreds of stupid things that plug into USB jacks are an example. They aren't communicating with the computers they connect to, but just taking advantage of a common low power DC source with a common connector.

As for a whole house transformer, another approach might be for a couple transformers, but not dozens. And similar to how a UPS works, it might not be a bad idea for some of these DC networks to be battery backed up. A DC source, the battery, and DC lighting would make for easier lighting in a power outage. Depending on the efficiency of the battery charging, it might even be worthwhile to charge the battery during off-peak times and run the lighting off of the battery during peak times.

Back to the orginal posting about LEDs. If you were to have all the ceiling fixtures in a house be LEDs, and you knew this before building the house, I'd suggest that running 120v AC to all those fixtures and building in transformers and rectifiers in each socket would not necessarily be the best approach.

Efficient Lighting

[falconwolf]

Thanks for the link, I bookmarked the homepage to explore the site. I noticed one thing on the page where it says there's a problem with Fluorescent lights, "Use halogen lighting for outdoor applications where temperature causes problems with fluorescents." I lived in Florida and never had a problem using them outdoors and I currently live in Minneasota and haven't experienced problems here either. I've lived and used CFLs in both heat and cold without problems.

Faclon