LED's efficiency exceeds 100%

led 100 efficiency — An LED’s power conversion (wall-plug) efficiency varies inversely with its optical output power. Wall-plug efficiency can exceed 100%, the unity efficiency, at low applied voltages and high temperatures. Image credit: Santhanam, et al. ©2012 American Physical Society

(PhysOrg.com) -- For the first time, researchers have demonstrated that an LED can emit more optical power than the electrical power it consumes. Although scientifically intriguing, the results won’t immediately result in ultra-efficient commercial LEDs since the demonstration works only for LEDs with very low input power that produce very small amounts of light.

The researchers, Parthiban Santhanam and coauthors from MIT, have published their study in a recent issue of Physical Review Letters.

As the researchers explain in their study, the key to achieving a power conversion efficiency above 100%, i.e., “unity efficiency,” is to greatly decrease the applied voltage. According to their calculations, as the voltage is halved, the input power is decreased by a factor of 4, while the emitted light power scales linearly with voltage so that it’s also only halved. In other words, an LED’s efficiency increases as its output power decreases. (The inverse of this relationship - that LED efficiency decreases as its output power increases - is one of the biggest hurdles in designing bright, efficient LED lights.)

In their experiments, the researchers reduced the LED’s input power to just 30 picowatts and measured an output of 69 picowatts of light - an efficiency of 230%. The physical mechanisms worked the same as with any LED: when excited by the applied voltage, electrons and holes have a certain probability of generating photons. The researchers didn’t try to increase this probability, as some previous research has focused on, but instead took advantage of small amounts of excess heat to emit more power than consumed. This heat arises from vibrations in the device’s atomic lattice, which occur due to entropy.

This light-emitting process cools the LED slightly, making it operate similar to a thermoelectric cooler. Although the cooling is insufficient to provide practical cooling at room temperature, it could potentially be used for designing lights that don’t generate heat. When used as a heat pump, the device might be useful for solid-state cooling applications or even power generation.

Theoretically, this low-voltage strategy allows for an arbitrarily efficient generation of photons at low voltages. For this reason, the researchers hope that the technique could offer a new way to test the limits of energy-efficiency electromagnetic communication.

Explore further: Darpa seeks new power dynamic for continuation of Moore's Law

More information: Parthiban Santhanam, et al. “Thermoelectrically Pumped Light-Emitting Diodes Operating above Unity Efficiency.” Phys. Rev. Lett. 108, 097403 (2012). DOI: 10.1103/PhysRevLett.108.097403
Physics Synopsis

Deathclock

3.4 / 5 (10) Mar 05, 2012

so, is it converting some of it's own material into energy or drawing energy from the environment or what?

Lurker2358

1.9 / 5 (35) Mar 05, 2012

right.

So LEDs are over-unity machines.

Wait. I thought the U.S,. patent office stance was that over unity machines don't work, which is why they turned down Rossi.

230% efficiency? Really?

So you invented a reverse-entropy machine eh?

Let's toss out all them text books, along with everything this site represents I suppose...

4.5 / 5 (31) Mar 05, 2012

Okay lurker tone down the crazy a bit, they are not describing a closed system... there is no reason it cannot have greater than 100% efficiency with respect to the electrical input if it is extracting energy from somewhere else.

Callippo

1.7 / 5 (24) Mar 05, 2012

U.S,. patent office stance was that over unity machines don't work, which is why they turned down Rossi

If the cold fusion is overunity machine, then the hydrogen bomb is perpetuum mobile. Cold fusion is not an overunity machine - it's a process, which is thermodynamically perfectly feasible, it's just believed to proceed too slowly under normal conditions. Rossi didn't get a patent, because he's the US government does want to give a monopoly to the future energy production to man, who isn't USA citizen. It's a political thing, as many similar devices were patented already in USA w\out problem.

El_Nexus

4.2 / 5 (10) Mar 05, 2012

So you invented a reverse-entropy machine eh?

Not quite. We tend to assume that because luminescence is useful it must be low in entropy, which it's not. It's less disordered than heat, but far more disordered than, say, mechanical work. By emitting luminescence, the LED reduces its own internal entropy but still increases the entropy of the universe as a whole.

3.2 / 5 (10) Mar 05, 2012

This LED is not 100% efficient, it just employs thermoelectric current instead of galvanic one. You can power the normal LED with thermocouple with the same result. In this rudimentary case the PN junction inside of LED just serves as such thermocouple. http://www.youtub...D2pxvxgU

2.7 / 5 (7) Mar 05, 2012

Callip:

I know Rossi's device is not an over unity machine.

But the U.S. patent office classified it as one nevertheless.

1.5 / 5 (15) Mar 05, 2012

I know Rossi's device is not an over unity machine. But the U.S. patent office classified it as one nevertheless.

I know and I provided an explanation for this nonsensical stance already. The USA are protecting their interests.

rwinners

1.7 / 5 (6) Mar 05, 2012

I'm doubting this... seriously. Conservation of energy, anyone?

Sooo - if we connect thousands of these lights together - and shine them on a pv panel that has more than 50% efficiency - do we get free energy? If we connect the output of the pv panel to more led's - shine them on another pv panel - and do that millions of times over - we could create a giant power plant! Just a thought....

No... This does not violate the first law of thermodynamics.

4.5 / 5 (8) Mar 05, 2012

Energy is being conserved. Heat is a form of energy, and it is being converted into light by this process.

rbrtwjohnson

1 / 5 (7) Mar 05, 2012

With a correct interpretation of the laws of thermodynamics, efficiencies closer to 99% are possible. Then a reverse-entropy machine, using rotating magnetic fields, can in fact realign disordered molecules in order to squeeze-out heat energy into electricity. http://www.youtub...k19hn7Rc

kochevnik

1 / 5 (3) Mar 05, 2012

http://www.youtube.com/watch?v=Uqnk19hn7Rc

Wow ok that's exceeding 100% of human knowledge.

Cave_Man

1 / 5 (2) Mar 05, 2012

I'm pretty sure you guys all missed the point by a mile. Nothing strange happens here except the fact that electrons are being converted to photons more efficiently.

I have a sneaking suspicion that when they say 30 picowatts to 69 picowatts they are simply using a standard of electrical energy which needs to be incorporated into quantum mechanical units.

kind of like how a charged hydrogen atom may yield a certain electron volt quanta but the total energy in the atom system is much larger than the available charge. One can assume since an electron is more massive than a photon that the higher the conversion efficiency the more the complex heavy electron is converted to simple lower energy photons.

They aren't making any free energy only freeing up what is there with greater efficacy.

nuge

4.6 / 5 (34) Mar 05, 2012

Jesus Christ, did any of you bother to actually read this relatively short and simple article? It says quite clearly that the extra energy comes from background heat. It's not some violation of the laws of physics or anything. Fucking read the article (all of it) before making retarded comments, PLEASE.

antialias_physorg

3.3 / 5 (8) Mar 05, 2012

Reminds me a bit how an electric motor can increase in speed when you disconnect it from the power source (feeding on the stored energy in the magnetic field until depleted - or until it exceeds its maximum designed speed which can destroy the motor)

I have a sneaking suspicion that when they say 30 picowatts to 69 picowatts they are simply using a standard of electrical energy which needs to be incorporated into quantum mechanical units.

I think it's much simpler than that. During operation the LED gets hot. When you reduce the voltage some of the heat gets converted into infrared radiation (additionally to the light generated by the LED). So for a short while we get more than is being put in from the wall plug - but not more than was put in over the entire time of operating the LED.

GrandM4x

5 / 5 (13) Mar 05, 2012

They are mentionning that the LED acts as a heat pump. It steals energy (heat) from the environment and therefore emits more energy than the electrical input. But not more energy than the total input.

Energy is conserved as it will always be.

1.7 / 5 (11) Mar 05, 2012

That's too easy to control for, and I hope these researchers aren't that stupid.

All you'd need do to control for that is use very short on/off pulses and measure the energy in vs energy out.

This way you avoid any hidden buildup of heat or other energy coming from the original power supply.

Graeme

not rated yet Mar 06, 2012

This amount of light should be visible if you can get it into a human eye, but not exactly bright enough to illuminate.

Richardmcsquared

1 / 5 (3) Mar 06, 2012

I'll say NO

Skepticus

1.3 / 5 (3) Mar 06, 2012

If this experiment is correct, it means they are dealing with an open system, since the input energy is used to produce an output that incorporates the thermal energy from the environment/atomic lattice of the led, not just from the input. It is much like a hydro power dam. With suitable arrangements (gates/ dam walls), you spend negligible amount of energy input to control the gates to the turbines and get much larger energy output out of it. Who cares if the entropy of the whole universe increases always, but we can use the energy here and now?

gwrede

3 / 5 (2) Mar 06, 2012

Let the marketing guys write the article, and this is what you get.

They take liberties, such as "forgetting" the thermal engergy use. That's like saying that "my bike that has an electric assistant motor, is 200% efficient" when actually I do half the work myself. I think this is downright childish.

Oh, and BTW, ever thought what kind of light you get with 10-8 watts anyway. So the whole thing is actually a lot of talk about nothing at all.

_ucci_oo

Too many people are fired up over this article. Chill, Brothers and sisters.Seems more people are making conclusions than the people doing the research.

antonima

4.7 / 5 (3) Mar 06, 2012

Right, only the second law is getting screwed.. its not like its the first time!

Unless it is meant to be a shock article, it is completely commonplace for a diode to emit light, even when no voltage is applied at all! Quoting a photonics textbook:

"At room temperature, the intrinsic concentration of electrons and holes in GaAs is n1 == 1.8 * 10^6 cm^-3. Since the radiative electron-hole recombination coefficient rr == 10^-10 cm^3/s, the electroluminescence rate Rrnp=RrN^2i == 324 photons/ cm^3-s... this corresponds to an optical power density == 7.4 * 10^-17 W/cm^3."

Photodiodes will emit light on their own, and a semiconductor with a lower bandgap will emit even more equilibrium light than GaAs. Since clearly this is a non-equilibrium system, there is probably more to it than just that.

Kedas

1 / 5 (1) Mar 06, 2012

So who in here is surprised we can also use the heat as energy source for light?
The question is who is heating it.

ShotmanMaslo

How does this not violate the 2nd law of thermodynamics?

SincerelyTwo

2.6 / 5 (7) Mar 06, 2012

You guys are actually stupid, I'll prove this with logic. This article's headline was designed by writers and does not reflect the underlying technology accurately. Most of you did not take the time to understand the underlying technology and assumed the writers accurately represented it.

So the fallacy here is that most of you decided to assume that the title of the article was truthful.

In point of fact the title is an out-right lie, and the technology is an open system and that, you fucking twats, does not violate the laws of physics. The implications of the title does, but again, the title is a lie.

Every comment here except one or two are a waste of time and life to read. If you are remotely intelligent and manage to get to my comment I urge to to move on to something else and forget this place, it's obvious that YouTube users have made this place their new home.

Kinedryl

The quantum mechanics allows the violation of 2nd law of thermodynamics - well, temporarily. I'd guess, in the meanwhile the charge carriers in LED would behave like black body and they would consume the light from outside, while generating thermal radiation. After all, you even don't need to have a PN junction for occasional spontaneous emissions of photons. http://www.physor...719.html

baudrunner

1.2 / 5 (5) Mar 06, 2012

This development will lead to the extinction of the battery, and fossil fuel based power plants, and hydro bills, and gasoline etc.

3.7 / 5 (3) Mar 06, 2012

A similar stuff: Self-Charged graphene battery (is supposed to) harvests electricity from thermal energy of the environment...

JRi

Looks like you need have your room temperature quite high (135C, 275F), to exceed 100% efficiency.

tpb

This was known at least 20 years ago when the first truly efficient infrared LEDs were invented.
Think of the LED as a peltier junction which when used to heat instead of cool, produces more heat on it's hot side than electrical energy put into it. The excess comes form the cold side and ambient.
The LED has a junction like the peltier device and can convert ambient thermal energy into photons instead of heat.

2.3 / 5 (4) Mar 06, 2012

This was known at least 20 years ago when the first truly efficient infrared LEDs were invented. .. The LED has a junction like the peltier device and can convert ambient thermal energy into photons instead of heat.

Wait, wait... Peltier junction needs a temperature gradient for being able to work. At the uniform environment it has no apparent reason to generate electricity in the same way, like the LED has no apparent reason to generate light.

http://www.techno.../27625/: Self-Charged graphene battery (is supposed to) harvests electricity from thermal energy of the environment...

Uh....................WHAT??

That is more than 100% awesome :-P

Grallen

not rated yet Mar 08, 2012

30 picowatts of electricity are being made more entropic by becoming light.

69 picowatts - 30 = 39 picowatts of heat are becoming less entropic by becoming light.

How much more entropic is heat than light? How much more entropic is light than electricity?

They say this continues to scale...

I pose this question: Is there a point where we can choose to make light, but do so without increasing entropy any more than it would have increased if left undisturbed?

This is little more than choosing the type of entropy created, but still intriguing.

Also another open question...

Electricity Heat converted to light then converted to electricity.

Potentially more efficient than: Heat converted to kinetic energy converted to electricity?

wdhowellsr

In the context of reality there are many things that make no sense. Einstein went to his grave trying to overcome the anomolies that became Quantum Physics. Yes it is possible to do what seems absurd at the experimental level but once we try to scale to reality it fails completely.

I'm am certainly not against amazing discoveries that change everything but it always seems that when we try to scale up to the normal world, everything changes.

There is not and will never be a free lunch in Physics.

1 / 5 (4) Mar 08, 2012

but it always seems that when we try to scale up to the normal world, everything changes.

AWT is just based on scaling the normal world up and down. In this model the Universe is just extended situation at the water surface: both in scale, both in number of dimensions. It has a good gnoseologic meaning, because we know quite well, how the real world is behaving, so we can extrapolate it to the less known areas. With compare to it, the mainstream physics relies to abstract ad-hoced concepts, so it builds its models from up to bottom and it's guessing often.

There is not and will never be a free lunch in Physics.

Actually the observable reality can be understood quite easily with dense aether model already, but the physicists aren't very motivated in having free lunch, because they need to prolong their jobs and salaries as long, as possible, as R. Wilson recognized before many years.

1 / 5 (3) Mar 08, 2012

The LED actually doesn't radiate with COP > 1 efficiency, because what is radiating are the occasional photons generated with quantum noise. The weak current used just decreases the potential barrier, which must be overcomed for it, but this is a whole principle of quantum tuneling or radioactive decay: if some particle can escape from atom trough finite potential barrier, then it will always escape from it - soon or later. In electric circuits it's quite normal, some current noise is passing back and forth even at zero voltage and this noise is actually an effect, which decreases signal/noise ratio of many sensitive measurements. So why some LED couldn't generate light noise at it's voltage threshold voltage? It's nothing, which cannot be deduced from classical physics.

5thabove

1 / 5 (1) Mar 09, 2012

"electrons and holes have a certain probability of generating photons." Wait a moment..holes are "imaginary" concepts invented to hold imaginary parts, not real parts like me! This reverse phase of time is not real according to experts, its just a concept like you..I'm the real one. Holes go with imaginary time that runs backwards so real time can go forward in mathmatics. An atom oscillates and has three parts..Humm. Now don't get mad but you know what? You might be after all. "Relative to the observer all other observers are behind it in time". "the Hall effect reveals positive charge carriers, which are not the ion-cores, but holes"

Time is happening now, Space is a 4th phase in time and the force carrier of gravity and is an element of time and part of energy that makes an atom. Atoms like ANYTHING that oscillate have 4 phases in time. The hole is not only the missing graviton in the S model, its a 4th part of the atom, a 4th part of the observer. U R all real after all!
JFH^^

wiyosaya

I hate to disappoint the over unity folks here; yet, perhaps a better title for this article would be as follows:

"LED's Coefficient of Performance (COP)Exceeds 1".

As I see it, either the author of the article did not understand the process for one reason or another, or the author wanted to be sensational. If the latter, that would be unfortunate, IMHO.

"Over unity" would require that energy is created from nowhere and an accounting of that energy output would reveal that there is energy that that seemingly came for nowhere. The article does not state that.

The article does indicate the the "extra luminosity" is derived from heat. Therefore, energy is conserved, and a detailed, accurate analysis of the system would reveal that all energy in the output can be accounted for from some source in the system.

There is no over unity here - unfortunately.

Rohitasch

not rated yet Mar 09, 2012

A good analogue for this phenomenon would be those glass cranes that have alcohol inside and they keep swinging, making the alcohol rise till they flip and dip their beaks into a cup of ether which cools the head and the alcohol falls and the swinging starts again.

James_Mooney

Yayyy! We finally got perpetual motion. I knew we could do it. Screw the electric company and the oil cartel. I'm going to go out and buy ten thousand LEDS, shine a flashlight on them, and have self-generating power for life ;')

Seriously though - we are converting ambient heat into light - which does seem to go against entropy.

Moebius

1 / 5 (2) Mar 10, 2012

Sooo - if we connect thousands of these lights together - and shine them on a pv panel that has more than 50% efficiency - do we get free energy? ....

If the PV panel is 100% efficient not 50% it sounds like you do have over unity gain.

If you have an individual 100% efficient receptor for each LED you should have a net gain of power and probably a thermocouple.

Szkeptik

not rated yet Mar 10, 2012

"electrons and holes have a certain probability of generating photons. The researchers didnt try to increase this probability, but instead took advantage of small amounts of excess heat to emit more power than consumed. This heat arises from vibrations in the devices atomic lattice, which occur due to entropy."

So they used the entropy of one part of the system to lower the entropy of the next part of the system? How does that even work?

DirtySquirties

1 / 5 (2) Mar 11, 2012

Wow! Look at all the physics experts we have commenting on this article! Simply amazing!!

it is completely commonplace for a diode to emit light, even when no voltage is applied at all

Actually this is what the Raman (anti-stokes shift) during fluorescence is about. Many quantum dots are working in the same way and they're actually formed just with PN-junctions like array of many LEDs. We can have antiStokes pigments, which do radiate visible light under illumination with infrared radiation. The lime light used in the 19th century is based on the same phenomena. During this the 2nd law of thermodynamics is violated heavily: just the heating of material is sufficient for production of visible light, the material is cooling itself during this bellow temperature of environment. After all, isn't the radiation of the hot body itself the violation of 2nd law of thermodynamics as such?

paul856

1 / 5 (1) Mar 15, 2012

If the LED is all at the one temperature, then it is a violation of the 2nd law to extract power from this heat energy (the article does not say there is a gadient).
So here's what is going on. The authors ignored the device's blackbody radiation, which at the temperature quoted is indeed more than the light power observed. The device needs only to exhibit a modulation of "blackness" with the applied current to account for the observed behavior.
Case closed.

1 / 5 (2) Mar 15, 2012

After all, the violation of 2LT is much more common, than you probably believe. For example, every thermoluminescence (like the candoluminiscence of lime light) apparently violates it, because it cools the objects, while it releases the photons of wavelength shorter, than it corresponds the Planck black body radiation.

The thermoluminescent pigments glow in visible light, while cooling its environment. The closed system composed of LED does the very same: it glows in visible light, while cooling its environment.

Strictly speaking, only if we would embeds the LED with graphene battery into black box, the energy of light absorbed in its walls would compensate the cooling of battery, so that this device wouldn't violate the thermodynamics in strict sense.

3 / 5 (2) Mar 16, 2012

(the article does not say there is a gadient).

The article says that the the LED cools.

Notice the following passages:

but instead took advantage of small amounts of excess heat to emit more power than consumed.

and

This light-emitting process cools the LED slightly, making it operate similar to a thermoelectric cooler

There is no miracle here. Excess heat is turned into light. In addition to the light produced via the electric current this gives you more light of that frequency than the current would alone.

1 / 5 (1) Mar 16, 2012

Again, there can be no thermal energy extracted from a system at uniform temperature, and the article does not state that any temperature gradient exists. Thus this would be a violation of the 2nd law.
I postulate that the authors are measuring blackbody radiation from their device which is modulated by the DC applied.
If their entire measurement system was at the LED temperature, then the LED would absorb as much light from the system as it thermally radiated. Its net light out would not be over unity of electric power applied.
Paul

there can be no thermal energy extracted from a system at uniform temperature, and the article does not state that any temperature gradient exists

Again:

How is 'excess heat' not a gradient?

No thermodynamic laws are violated anywhere in this.

not rated yet Mar 16, 2012

I cannot find any mention in the original paper showing a nonuniform temperature within the LED. Therefore, no heat energy from within this(LED) system is available. To claim to have extracted this energy from a uniform temperature system is a basic 2nd law violation.
I calculated also that the blackbody radiation is indeed greater than the light output observed (making some assumptions of the size of the device; it wasn't exactly specified).
Energy will flow from the hot LED to the colder lab. This is called blackbody radiation, not a hyper efficient LED.

1 / 5 (2) Mar 16, 2012

To claim to have extracted this energy from a uniform temperature system is a basic 2nd law violation.

In nature many phenomena violate the basic 2nd law. Wwhen termoluminiscent pigment produces more noble (i.e. higher frequency) energy into account of thermal radiation, it violates 2nd law of thermodynamics.

DustinS

The summary says that more than twice the electrical energy being expended is being emitted as photons and that the extra energy comes from heat in the diode, resulting in a net cooling effect.

Has anyone here actually read the article to see if this is correct? (a copy would be nice but not for $30).

If this is correct, then a lot depends on the intensity & wavelength of the emitted photons relative to the LED's blackbody radiation (both of which affect the maximum theoretical solar panel efficiency). Unfortunately, neither the wavelength distribution nor the LED size are mentioned in the summary.

It should be noted that the 2nd law of thermodynamics is an unproven mathematical theorem even for classical mechanics (this was mentioned in my statistical mechanics textbook and the professor put it in a list of things that you would get a Nobel prize for either proving or disproving).

not rated yet Mar 20, 2012

I did find the whole paper and read it. I don't remember the site; I just searched for the full title. The device was at 135C and its peak output shown was 2.4 microns (not quite the peak wavelength, but within the range of significant thermal radiation). The exact dimensions were not given, but one plot showed a scale of twenty microns or so between contacts. I calculated that the total blackbody radiation is indeed more than the few picowatts quoted.
By the way, I don't know of any proven 2nd law violations, And I have disproven some other claimed violations before.

Paul

Fumfum

not rated yet Apr 13, 2012

1) This isn't defying natural physics.
2) This is not a "unity" device.
3) However, this is showing efficiency in energy conservation by breaking yet another testing mechanism.