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Photonic Structure Increases Light Bulb Efficiency
An Anonymous Coward writes "A new experimental microscopic tungsten lattice
can increase the efficiency of an incandescent
electric bulb from 5 percent to greater than
60 percent. This is done by converting waste
heat into visible light. "
IR seems to be the first thing people get when they're working with things that produce light. I believe IR LEDs were the first LEDs, and IR lasers were the first light emitting lasers.
Second, I love this. They don't even have a THEORY on why this works. It just does.
Third, If they get it working in the visible light spectrum, they'll have a bulb that's SIXTEEN time more powerful than tungsten bulb.
That's one hell of a flashlight. I'll call mine "Little Boy". I promise to only use it in self defense. And to start small fires.
Democrats or Republicans. They are both taking us to the same place and they are not afraid of us anymore.
Infra Red is a lower (longer) wavelength than visible light. It makes sense to get it to work at the lower (probally easier) wavelegnth and then 'take it up a notch' into the visible spectrem. This is exciting for it's energy efficiency and the fact the light remains a point source (good for fixture design).
I wonder how the matrix holds up as the tungsten evaporates from the filiment?
SD
âoeWho knew something as harmless as willful ignorance could end up having real consequences?â
couldn't resist:
Q: How many programmers does it take to change a broken light bulb?
A: None, it's a hardware problem.
My understanding is that they said that IR-frequencies are synonymous with "heat". They frequently used the term black-body radiation. I remember IR-HEAT being associated with green-house effects; the angle of refraction is low for IR and glass, for example. So when sunlight enters your car (at a direct angle), it bounces off things but hits the glass on the inside at too great of an angle, and thus bounces back inwards, amplifying the total heat.
Not that I'm satisfactorily answering your question, but throwing out some food for thought.
-Michael
-Michael
Three-dimensional (3D) metallic crystals are promising photonic bandgap structures: they can possess a large bandgap, new electromagnetic phenomena can be explored , and high-temperature (above 1,000 C) applications may be possible. However, investigation of their photonic bandgap properties is challenging, especially in the infrared and visible spectrum, as metals are dispersive and absorbing in these regions. Studies of metallic photonic crystals have therefore mainly concentrated on microwave and millimetre wavelengths. Difficulties in fabricating 3D metallic crystals present another challenge, although emerging techniques such as self-assembly may help to resolve these problems. Here we report measurements and simulations of a 3D tungsten crystal that has a large photonic bandgap at infrared wavelengths (from about 8 to 20 m). A very strong attenuation exists in the bandgap, 30 dB per unit cell at 12 m. These structures also possess other interesting optical properties; a sharp absorption peak is present at the photonic band edge, and a surprisingly large transmission is observed in the allowed band, below 6 m. We propose that these 3D metallic photonic crystals can be used to integrate various photonic transport phenomena, allowing applications in thermophotovoltaics and blackbody emission.
Doesn't this look like some explanation: the material (unlike metals) has a bandgap, i.e., is insulating and cannot absorb or emit radiation at low frequencies. So the energy has to be dissipated at higher (visible) frequencies. Apparently the output is higher than naive calculations would predict. So the puzzle is not why the frequency of the emitted light is so high, but why the output is so strong for a given temperature.
They last longer too. Just had one fail, for the first time in 5 years. It was a bit of a shock, I can tell you. I'd forgotten all about buying replacement bulbs.
Government of the people, by corporate executives, for corporate profits.
light bulb wastes power
tungsten evaporating:
produce more photons!
And what about when my daughter finds a birds nest that has fallen out of a tree and we need to fabricate a incubator out of a box and a 25 watt light bulb to keep it warm?
This is horrible news. Think of the children. Call your congressman and ban this insanity.
A 60% efficient incandescent bulb would have a whole lot of applications beyond just saving money on the power bill.
Think projector lamps: Think about the waste heat they wouldn't generate. Think about the cooling fans they won't need. Imagine a 40-watt bulb throwing as much light as a 500 watt bulb does today.
I sure hope this hits the market sometime SOON.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
60% is positively huge, although I wonder how cheaply they'll be able to put microscopic tungsten lattices in flashlight bulbs and relatia.
Much more profound though is that they're basically talking about a device that converts heat into light: The ramifications and applications of that are wide ranging and staggering. Getting even more "goofy", could you have a heat->light conversion, followed by a light->electricity conversion? (i.e. a small "heat energy recovery system").
Well, I'm an undergraduate Electrical Engineer, so I only have superficial understandings of how semi-conductors interact with light, but it doesn't seem too great a stretch of the imagination.
First, semi-conductors work based on the principle of the band-gap (which they even mentioned) (correct me if I'm wrong with any of this, I'm doing it straight from rusty memory).
A little background:
The outer 8 electrons held by an atom are the most important (the valence) - They are responsible for the bonding of other atoms. The configuration of all the electron orbitals in free space is nicely geometric; the first two electrons form a spherical shell (s-shell), the second 6 form dumb-bells in each of three axis's (p-shell). These types of configurations affect the geometries of the connection of the atoms. Configurations get more complex as the number of electrons grow (which is somewhat independent of the atomic number (number of protons), but such ionized atoms are unstable; especially when the number of electrons differs dramatically from the #protons). The important thing to understand here is that each additional electron takes more energy. Instead of worrying about the geometries, you can plot each electron orbital at a different (successively higher) energy level. Different atoms (characterized by atomic-number and even, to a small degree, the number of neutrons present), have differing characteristic energy-levels. The discrete nature of atoms includes the probabilistic nature wherein electrons have an extremely high probability of occupying the exact energy levels (which can be thought of as the distance away from the center of the nucleus). There is a chance that an electron will pass through any point around the shell of an atom, but it's highly unlikely that it will deviate from its characteristic point.
But, since different atoms have different characteristic levels, warping an atom will warp its points. Warping can occur by simply placing two atoms near each other (such as in an ionic or covalent bond). As it happens, when you squeeze atoms closer and closer together, the discrete lines that represent the energy levels start to merge together. Eventually the 8 outer valence bands merge into one continuous band... As you squeeze them even closer together, this band breaks into two continuous pieces. As you get even closer together, these pieces get further and further apart (I would presume that eventually one of these bands starts to merge with preceding energy levels, but that's not relevant here). This gap of continuous energy levels is called the band-gap.
As it turns out, in perfectly bonded atoms (those where every electron in the valence layer are bonded, and each atom has exactly 8 outer electrons; such as carbon, Silicon, etc) we have a total of 4 electrons that fill the inner continuous shell and 4 electrons that are void in the outer continuous shell. BUT, that outer shell is looped across neighboring atoms. When a diamond-lattice is organized (which is as close as you can possible get multiple atoms to sit next to each other), you have the greatest band-gap you can get for that particular element. Different elements (or even molecules) that can form the diamond-lattice will have differing characteristic band-gaps. What we have here are 4 electrons that are tightly tied to a core atom, and 4 potentially absorbed electrons that can freely be shared across every single atom in the entire crystalline lattice. In semi-conductor crystals, the problem is that every electron is accounted for so there are no free electrons to put into the outer band (which could roam free as current through an almost zero-resistance substrate; due mostly to quantum effects). Impurities are therefore inserted into the crystalline lattice which act as ionic donators of electrons or ionic acceptors of electrons (namely atoms not in the 4-column of the periodic table). Thermal excitation (heat) causes an electron to be ripped from donor atoms and those which are then quickly swept up in the outer-most continuous band.
Normally, electrons must have a precise energy-value in order to live in an atomic orbital. When an atom absorbs an electron, it gives off a photon of the remainder of the energy. To change orbital-levels, it has to accept a photon of exactly the correct amount of energy. It can accept a larger energy photon, but it will again give off the remainder of energy. Eventually that excited electron will fall back to its lower energy level, giving off another photon which will have the exact energy as the distance between the two energy levels.
In the continuous region of these silicon atoms, excitation between energy levels isn't apparent, since an electron can have any value within the region. The only difference is that separating the band gap... An electron from the inside can jump into the outer band if it's given at least enough energy to make the jump... This gap is usually enormous for semi-conductors. I believe its 1.2 electron Volts for Silicon, and 10 electron Volts for Carbon. The 1.2V is within the range of thermal excitation. That means that heat (in the form of vibrating atoms in the crystal) is enough to shake an electron free; e.g. jump the gap (like water successfully spitting to the lid of a boiling pot). In carbon, however, room-temperature heat is no where near enough to make the jump. This property (along with others) is why we don't use carbon-based semi-conductors. Germanium and silicon are much more practical in our particular earth climate.
There is another aspect to the band-gap that is relevant to our discussion. Each electron has not only an associated energy, but a quantum-form of momentum. You must not only have conservation of energy, but conservation of momentum. I'm a little fuzzy on this topic, but this momentum is represented by the letter k, and we can plot energy verses k for different things. For semi-conductors, we get parabolas, and inverted parabolas, but with discrete points. This says that while we have a continuous set of energy levels within a region, we have only a certain set of allowable energy+momentum values for the electrons. And like the discrete energy levels of atomic orbitals, you can only have one electron occupying a given state. In a rather unfulfilling way, I'll stop talking about things that I don't fully understand and simply say that this multitude of characteristic parabolas says that in order to have an electron jump, you have to not only have a precise amount of energy absorbed or emitted, but you have to be able to transition your momentum somehow. Energy transition occurs through photons, and momentum transition occurs through phonons - which is energy present in lattice vibrations (e.g. packets of heat).
Gallium arsenide is an example where the lowest point of the upper parabola and the highest point of the lower inverted parabola are aligned with respect to momentum. This means that the smallest amount of energy needed to make an electron jump the gap requires zero change in momentum. Because of this, gallium arsenide crystals easily will easily absorb or emit light with no dependence on the heat of a lattice. For this and other reasons, GaAs is great for laser diodes. Silicon, on the other hand requires a momentum change for its lowest energy transfer. Thus lots of heat is generated and absorbed; (Not to mention that silicon doesn't conduct heat as well as some other semi-conductors).
Given this superficial description, what I get out of this is that heat of a certain resonant point (in the form of vibrating atoms in the crystal) could provide the proper momentum shift needed for efficient electron excitation. You'd still need to provide photonic energy for the transition, but you'd have a perfect combination of heat + light absorption. Eventually (due to statistical decay), the electrons would fall back to their lower-energy-level states. But they'd give off light of specific frequencies.
Putting all this together, my initial impression from the article was that that the tungsten injection into a silicon substrate change the characteristic e-k curves enough to absorb the phonon-heat generated by IR light. The result is a 60% efficient absorption of the heat + light (e.g. nearly perfect efficiency). That energy is retransmitted as diode light (e.g. an exact energy level transition, producing a constant level of energy photons, which requires an equally constant frequency of light).
What I don't know at the moment is if this is actually emitting mono-chromatic light, or if a multitude of frequencies (e.g. white-light) permeates. The only way I could see white-light emitting is if the standard tungsten light-bulb is making it, and the Tungsten semi-conductor is amplifying a particular frequency.
-Michael
The science of turning electric power into light has really changed in the past decade. I've seen a graph in one of my engineering trade journals showing the efficency of LEDs in lumens per watt. Just a decade ago, the best LEDs were two orders of magnitude less efficent than flourescent bulbs. Now, the new generation of blue and white LEDs are more efficent than flourescent, and are approching the levels of low pressure sodium lights.
If we extrapolate from the given 5%->60% levels given in the article, that would raise incandescent lights to nearly the levels of flourescent, without the warm-up time flourescent has.
Now, the problem with LED vs. flourescent is cost - LEDs are much more expensive in terms of lumens per doller than flourescent. Would microstructured tungsten be any cheaper?
www.eFax.com are spammers
This would make for an incredibly cheap and effective night vision system with a small battery and a CCD camera. IR floodlight with 60% efficiency... mmmmmm.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
Damnit.. Forgot to append the best link in the world that describes this in detail.
Britney Spearse Guide to semiconductors
-Michael
Incandescent lamps... around 20 lumens per watt. Fluorescent lamps... about 70 lumens per watt. White LED, 50 lumens per watt and climbing. And the power requirements and ability to fit them into small spaces are much less tricky than for fluorescent.
LED's are almost there--and efficiencies are climbing. Main problem right now is that they're expensive. But already, I see they're being used for the red, and, increasingly, the green lights in traffic lights around here.
By the time this stuff makes it out of the lab, LEDs will be cheap and even more efficient than they are now.
And, of course, all the gee-whiz wizards-of-the-labs articles never say how much the new technology is likely to COST. And the stated efficiencies tend to decline as the devices start to approach reality...
If they can really make these things twelve times as efficient as LED's AND give a pleasant, flattering light spectrum AND get the cost down, it will be interesting.
"How to Do Nothing," kids activities, back in print!
Yeah, incadecent bulbs flicker at 120 Hz (both the positive and negative current phases heat the filament), but only by a few percent. It is easy to see with an oscilloscope, but not perceptable.
Every flourecent bulb I have seen flickers by almost 100%, and while it is not usually visible unless the bulb is failing, can still cause fatigue.
Much more importantly is that incandecent bulbs have a more natural color spectrum than most flourecents, since they work by black body radiation. I don't know why the "full spectrum" flourecents are not more popular, but they can really make a difference.
There's no such thing as a USian.
You see, some countries in the world are called "The United States of X". Generally because, accurately or otherwise, they're supposedly a federal union of autonomous "states".
People who live in one of these "United States" countries are called after the place where the states are located.
Citizens of the United States of Mexico are called.... Mexicans.
Citizens of the United States of Brazil are called.... Brazilians.
Citizens of the United States of America are called.... Americans.
But the entire Western Hemisphere should be called "America"! It's unfair that just the USA uses that name!
Unfair in what way? Brazil doesn't lack a name. Canada's not hurting for a moniker unrelated to the name of its continent.
Besides, geographical names are blurry anyway. By "Africa'' a lot of people mean simply "sub-Saharan Africa". Peru used to mean all of non-Brazilian South America, not just one Andean country. Some names (e.g. Iraq, Pakistan) are simply made up out of nowhere.
So why invent the ugly term "USian", which could equally well apply to several different countries, when everybody the world over knows what an "American" is?
All employees must wash hands before seeking equitable relief.
This is great work. But if people want high-efficiency, pleasant-looking light-bulbs, they can already get them and save money in the process. The fact that people don't buy them despite all their advantages suggests that the problem isn't technology, it's people.
Because some idiot decided that there needed to be 3600 seconds in an hour, and so using a 100W device for an hour somehow uses 360kJ of energy.
If your target audience uses a calculator to get fifty percent of a hundred, you don't want to inflict our silly Sumerian time scale on them. (Was it the Sumerians who did the base-sixty nonsense? Or was that the Babylonians?)
--grendel drago
Laws do not persuade just because they threaten. --Seneca