Quantum light: The plastic lamp containing an array of LEDs screws into a standard recessed ceiling socket. The yellow-tinted optic on the surface contains quantum dots that convert the light into a better white hue.
QD Vision
QD Vision is using its quantum dots in LED lighting to produce more pleasing white light.
Seth Coe-Sullivan flicks the switches on two desk lamps, and even from across the conference room, it's immediately obvious which light the chief technology officer of QD Vision is there to brag about. The light coming from the lamp on the left is a harsh bluish white. The lamp on the right casts a warmer, more yellow glow. Coe-Sullivan holds a hand under each lamp. The hand under the bluish light looks pale and sickly; the other looks darker and healthier. The harsher light lacks wavelengths in the red end of the spectrum, so there's no light to illuminate the reddish tinge that blood provides to human skin.
QD Vision, based in Watertown, MA, is promoting a new LED-based lamp that it made with Nexxus Lighting of Charlotte, NC. Nexxus makes a lamp designed to screw into standard sockets used in recessed ceiling lighting. It consists of an array of white-light LEDs encircled by fins that remove excess heat. QD Vision adds an optic--a plastic cover with a special coating that snaps into place over the LEDs.
It's that coating that makes the difference in the quality of the light. It consists of quantum dots--tiny bits of semiconductor material just a few nanometers in diameter. When excited by a light source--in this case, the LEDs--quantum dots radiate light in a wavelength that varies according to the size of the dot: a two-nanometer dot gives off blue light, a four-nanometer dot emits green, and a six-nanometer dot produces red. The company makes the dots in controlled sizes, then mixes them in the right ratio to get the desired color.
This color-tailoring ability solves one of the major problems with using LEDs for general lighting applications. LEDs are appealing because they last for years, use perhaps 20 percent of the electricity of a standard incandescent bulb, and are highly efficient at converting electricity into visible light instead of into heat. But to make white light, you either have to mix together LEDs of different colors or use a blue LED coated with a phosphor that emits yellow light to produce a whitish mix. The problem with the phosphors is that they don't emit evenly across the visible spectrum. They tend to have gaps in the green section and even more so in the red, leading to the harsher, bluish light. "You can't precisely tailor phosphors anywhere in the visible spectrum," says Dan Button, QD Vision's CEO.
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No major benefit in efficiency vs CFLs
They quote an efficiency of 65 L/W for their LEDs.
They then say that CFLs generate 30 L/W, but CFLs are in the range 50-60 L/w, and so there is no real energy advantage (apart from a good CRI) for a bulb that costs about 20x as much.
They should license the dot technology to the whole LED industry and let other people get the price down.
Re: No major benefit in efficiency vs CFLs
WalMart sells a bulb that looks like this for a price in the $40s.
My limited experience is that while they are fine for dramatic effects, they won't bathe a room with light like incandescents and CFLs.
Re: No major benefit in efficiency vs CFLs
I agree 65 lm/W is not very impressive and CFL are better than 30 lm/W. Cree, Phillips, Nichia all have LED’s that operate at much higher efficiencies, 125+ lm/W and higher. The other question I have is how much power is the device operating at? In other words how bright is it? They show the fins so presumably the array generates some heat, but is that simply because of low efficiency?
To get a brighter LED, more power is needed and then the whole system (diode, encapsulant, phosphor, and lens) get hotter. The ability to run hotter for a very long time really has to be in place if this technology is to be successful. Otherwise too many devices will be needed to get the brightness up and then costs will kill you. A few years ago 100$/ bulb for 65 lm/W might have actually been competitive with the industry, but they have made some nice strides in recent years.
If this method is heat stable there could also be a competitive advantages over YAG type phosphors since those loose efficiency with temperature. Thus there is some diminishing returns when running the devices at more and more power.
Interesting technology.
Re: No major benefit in efficiency vs CFLs
If the phosphors in CFL's are really so bad, why not use quantum dots there too? Answer may be a surface area vs light concentration question if these dots are expensive for some reason.
I'm very upset by how bad the driver circuitry is in the many LED lamps I have bought is. No one seems to think it is important to deal with dimmer switches or FET on/off switches, and since every light in any prosperous American home is a FET (in an x10 or photocontrol or motion sensor) now a days, it is annoying that the bulbs don't work at all.
I've also experience the low life span for LEDs.
But what would really make a great product is an LED light that decided to dim with declining AC power compatible with an incandescent. This could easily be designed in. Burning out with low power AC is NOT the right feature.
So let me ask one question: if LED's are so efficient, then why does this lamp need all the cooling fins? Cooling fins = the production of excess heat = inefficiency. Neither incandescent lamps, nor CFL's, nor any other kind of lamp that I know of, need cooling fins.
Maybe this also has to with why these LED acrays don't seem to last nearly as long as they ought to. Maybe they're extremely sensitive to the least amount of overheating.
It is nice to know something is being done about the color. It would be better if the article could quote clearly what the efficiency is of the quantum dot filter itself. One can infer from the other numbers given that it's quite high, but it's not stated anywhere.
And - $65 is the target?! Come on. I would say it would have to be less thas $10 to really get any traction. I don't really think a $65 bulb could possibly pay for itself in energy savings even over it's long lifetime. And in five years something far cheaper and more efficient and longer lasting will probably be available.
LEDs have the large heat sink because they are very heat sensitive. Since they are semiconductors, think of LEDs as being somewhat like microprocessors in terms of thermal management considerations.
That being said, I've noticed that many manufacturers are apparently unfamiliar with Ohm's low because they fail to properly drive their LED products. They overdrive them in order to get dazzling brightness as well as fail to adequately heat sink them in order to make the fixture fit into the standard light fixture form factors. LEDs want to be COLD, but heatsinks are expensive and cumbersome, so manufacturers cut corners and end up with substandard products that don't last long.
I once had an led headlamp burn out on me, and when I took it apart, I found that they were driving the 5mm white leds at around 100 milliamps each. Not only is that bad on the battery, 30 milliamps is considered the upper threshold for these devices. And this was an expensive headlamp from a reputable manufacturer. No wonder the light burned out prematurely.
Another heat related question: For those of us in cold climates, what is wrong with incandescent bulbs in the winter? The heat they create is a useful by-product, especially in a passive house where all heat sources are important. Cost per unit of heat may be greater than oil or gas, but the energy is not entirely wasted as most analyses have it. Incandescents should not be run if you have a/c on, but apart from that, what's the big deal?
LED payback can be escalated when these are installed in Office Buildings where the cost of labor to replace bulbs every year or two is factored in.
If an LED bulb lasts 14,000+ hours - or about three to four years under normal office hour conditions, then they have value from both the energy offset as well as labor replacement costs.
In "union" supported office settings, this can be quite a cash-cow.
What about the vagaries of life?
No way I'd ever put a $65 bulb in a lamp! If it gets knocked over, that's $65 gone.
And what about surges from lightning strikes? Incandescents are pretty resistant to this. Can the same be said for LEDs (not to mention CFLs)? I doubt it.
And how about thieves? Nobody would bother stealing a $1 incandescent. Probably not a $5 CFL. But a $65 LED bulb? Burglars will be breaking into houses, stealing the bulbs, and leaving the widescreen TV.
So much for the supposed 7 year lifespan.
After reading how quantum dots are made, anyone could do it in their basement or backyard if they had the time and equipment. So why is it so expensive? As for LEDs, I have 2 tiny units that emit red, white and blue like a police car mounted on a remote controlled race boat. Both LEDs are powered by 2, 1.5v watch batteries. They are quite bright and can be seen very easily even in the day time. I have a white LED flash light powered by a single 1.5v AA battery that you can't look at or it hurts the eyes, its so bright. So, 3v or under to trigger the LEDs, how many LEDs do these "$65.00" lights need? There doesn't appear to be any requirement for either the price or the fins
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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jmaximus9
86 Comments
Cost needs leap first
I don't care how good it works when a standard light bulb can be bought at WalMart for less than a dollar and these cost about $100. It would take my lifetime to payback the difference. Also these compact florescent light bulbs do not give off the light they claim, nor do the last as long. So I am skeptically that these bulbs would really last for 40,000 hours.
Reply
hankejh
20 Comments
Re: Cost needs leap first
I agree - these are a total rip off at $40-100. I have used a broad variety of LED "bulbs" over the past two years - none of them lasted more than a few thousand hours. They're all crap with wrap-around marketing.
I've also achieved a warmer light cast by using yellow/orange markers - this worked quite well, but the LEDs eventually die (and not in 40,000 hours - most were dead around 4k hours, some sooner).
Reply
wookey
2 Comments
Re: Cost needs leap first
In fact over 10 years of nightly lighting (say in living room) the difference in running cost between on old incandescent and one of these LED lights is about $400 (at 30cents/kWh which seems like a plausible average price over the next 10 years (at least in the UK - I don't know what expected prices in the US are). So if the bulb really does last for the 14,000 hours in question then you will save $350-odd.
So it really is worth investing in low-power bulbs, even expensive ones like this, in well-used areas. CFLs are nearly as efficient (30-50lumens/watt) and also very cheap so if you don;t like the upfront prices get those instead. But in fact what you really want is the most efficient lights money can buy.
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Tysto
34 Comments
Re: Cost needs leap first
And the cost of replacing a dog every 8-10 years dictates that you buy a tortoise.
Reply
Shiladie
56 Comments
Re: Cost needs leap first
Tysto, what they are commenting on, is that this new light's benefits over other LED lighting schemes, are not benefits over the classic 1$ vacuum bulb.
This is more like paying 1000$ for a dog that lives a bit longer, or 10$ for a normal dog, yes worth it for some, not for the general public.
Reply
briang1621
173 Comments
Re: Cost needs leap first
Your totally spot on, 95% of consumer look at price verse longevity. Plus anything more than $5 per bulb is just a novelty!
Brian Glassman
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