# MIT develops 200% efficient LED



## Chrontius (Feb 13, 2013)

No, really, hear me out before you say I'm violating the laws of physics here. 

http://www.lighting.co.uk/news/mit-...s-its-surrounding-environment/8627537.article

The way it works is that for every 1 watt of electricity you put in, 2 watts of light comes out. Where does the excess energy come from? It comes from the heat sink. Might I be so bold as to suggest dense arrays - possibly pixel sized - of this new LED with conventional LED dice in order to create an array approaching 100% efficiency? Based on ambient temperatures, and environmental energy sources, it could throttle power between the hot and cold running LEDs to maximize efficiency while not pushing any of its components past thermal operating limits.


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## Norm (Feb 13, 2013)

Chrontius said:


> 2 watts of light comes out.


I've never heard light measured in Watts before, even a 60 Watt light bulb has a lumen rating, 60 Watts is just a measure or the energy used.

Norm


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## awenta (Feb 13, 2013)

So the equivalent of two watts is emitted. Not bad. Double output and the same runtime.


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## slebans (Feb 13, 2013)

Norm said:


> I've never heard light measured in Watts before, even a 60 Watt light bulb has a lumen rating, 60 Watts is just a measure or the energy used.
> Norm



To calculate Wall Plug Efficiency(WPE) as a percentage value:
WPE =Radiant Flux Out(watts) / Power In(watts)


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## jtr1962 (Feb 14, 2013)

A more accurate description here might be an LED which converts both heat AND electrical power into light. In a closed system, the LED would be less than 100% efficient. It's only 200% efficient if you only account for the electrical power input, not the heat input. Very intriguing however. Put the heatsink in an insulated box and you'll end up with both light and cooling.


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## Norm (Feb 14, 2013)

slebans said:


> To calculate Wall Plug Efficiency(WPE) as a percentage value:
> WPE =Radiant Flux Out(watts) / Power In(watts)



Plug in 200% efficiency and tell me what the answer is.

My statement stands for the case given in the OP.

Norm


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## AnAppleSnail (Feb 14, 2013)

Emitting an extra 40 picowatts of infrared light helps, but you will not cool a closed box containing a billion of these LEDs. As cooling goes, it's an interesting heat pump, but not yet a light source.

I'm on my phone and can't get to the last.round of discussion from a few months back.


Edit. Norm: invisible light has zero lumens per watt. It's possible to measure the energy carried though.


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## bose301s (Feb 14, 2013)

Norm said:


> I've never heard light measured in Watts before, even a 60 Watt light bulb has a lumen rating, 60 Watts is just a measure or the energy used.
> 
> Norm



Well it is, and even things like the XT-E Royal Blue list their output in watts. Light is just energy thus can Bea measured in power.


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## Norm (Feb 14, 2013)

*Watts versus lumens*

Photometry

Watts are units of radiant flux while lumens are units of luminous flux. A comparison of the watt and the lumen illustrates the distinction between radiometric and photometric units.

The watt is a unit of power. We are accustomed to thinking of light bulbs in terms of power in watts. This power is not a measure of the amount of light output, but rather indicates how much energy the bulb will use. Because incandescent bulbs sold for "general service" all have fairly similar characteristics (same spectral power distribution), power consumption provides a rough guide to the light output of incandescent bulbs.

*As mentioned by slebans*

Watts can also be a direct measure of output. In a radiometric sense, an incandescent light bulb is about 80% efficient: 20% of the energy is lost (e.g. by conduction through the lamp base). The remainder is emitted as radiation, mostly in the infrared. Thus, a 60 watt light bulb emits a total radiant flux of about 45 watts. Incandescent bulbs are, in fact, sometimes used as heat sources (as in a chick incubator), but usually they are used for the purpose of providing light. As such, they are very inefficient, because most of the radiant energy they emit is invisible infrared. A compact fluorescent lamp can provide light comparable to a 60 watt incandescent while consuming as little as 15 watts of electricity.

I stand corrected, I never said it was wrong. I said I'd never heard of light output measured in watts. I still can't get my head around anything being 200% efficient.

Norm


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## Gregozedobe (Feb 14, 2013)

Norm said:


> .... I still can't get my head around anything being* 200% efficient*.



Think of it working like a house heat pump heater. You use 1Kw of electrical power to run an electric motor which runs a heat pump to extract 2Kw of heat from the outside air. So there isn't any magic going on (but if they can get it to work efficiently as a practical portable light source it will be great, particularly for lights used in warm climates, but possibly less efficient where snow and ice abound).


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## AnAppleSnail (Feb 14, 2013)

Nothing is 200% efficient. And this isn't yet practical. Without some _very advanced_ ability to control things, this will not be useful. Who needs a few picowatts of low infrared output? Very few instruments.

Watch out, I'm going to try to explain quantum physics: The way this works seems to require some electrical energy to change the LED's atomic ground state. Then because of the nonrandom way vibrations pass through the semiconductor lattice, some few atoms are 'bumped' to a higher state that lets them shed a deep-infrared photon. This energy leaves the LED. Taking energy away requires conservation of energy: So heat leaves the LED. The visual in my mind is that teensy ripples (Lattice vibrations) can combine under the right conditions to create taller sprays of water (Infrared photons). Energy is conserved overall, but 'bursts' happen that stand out from the background.

It is exactly an optical heat pump. If you gathered a few billion of these on a chip (The size of a Pentium, say) then one would need a few watts to get a few more watts of output. This 'discovery' dates way back and does not scale well... Yet. If we can create interesting metamaterials whose structure is conducive to 'springing' like this, maybe we'll get to useful band gaps that create visible photons.

But I don't think that it will ever become a high-power thing just because quantum effects don't scale well. As an example: The electron of the hydrogen atom of a particular water molecule in my left finger could be anywhere. In Germany, back home, inside the moon, or arbitrarily far away. But there is a probability that it is close to where we expect. The odds against that whole molecule, or my whole finger, being at an arbitrary position are near zero in the mathematical sense.


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## 2xTrinity (Feb 14, 2013)

This is basically a heat pump, and calling the device 200% efficient is misleading. The usual term for heat transported / electrical power for heat pumps (heaters or refrigerators) is "coefficient of performance", not "efficiency".


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## Hooked on Fenix (Feb 15, 2013)

So let me see if I understand this correctly. This l.e.d. gains it's efficiency from not only electrical current but also drawing in energy in the form of heat from the surrounding environment? If this is the case, wouldn't the l.e.d.'s efficiency be dependant on the temperature of the surrounding air? This would make it great in warm climates, but not so great in the cold. I don't see where they could call it 200% efficient if a reduction in temperature lowers efficiency.


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## Anders Hoveland (Feb 15, 2013)

2xTrinity said:


> This is basically a heat pump, and calling the device 200% efficient is misleading. The usual term for heat transported / electrical power for heat pumps (heaters or refrigerators) is "coefficient of performance", not "efficiency".


Except that the output energy has a significantly shorter wavelength than the wavelength correlating to the input heat energy.

By your type of logic, an LED powered by a solar panel is just a heat pump also.

Sorry, but it is not merely just a heat pump if the input energy is being turned into another more useful form of energy. We can argue about entropy here, _presumably _the entropy increase converting the electric current to light (or infrared as the case may be) is greater than the entropy decrease converting the ambient heat to light. But let me point out that we do not necessarily know this is the case. Since light can be converted back to electrical current, could this imply that entropy could actually be increasing in this situation? 

Let's not forget that the second law of thermodynamics is just a generalized statistical rule, not a _fundamental_ law of physics. If our line of reasoning happens to violate thermodynamics, that does not necessarily mean the line of reasoning is wrong. (another example of this is that "planck's law of blackbody radiation" is not a fundamental law either, and has been observed to be violated in photonic crystals)

Of course, for ambient heat energy (without a gradient difference) to be converted into an electric current, the extra efficiency of the LED would have to exceed the efficiency of the photovoltaic cell (the product of the two percentages decimal equivalent would have to be greater than 1). If finding such an LED and photovoltaic cell that can satisfy the requirements is not possible, does this imply entropy cannot be decreasing? I do not think so, at least not necessarily. The maximum practical efficiency of the photovoltaic cell may be more of a technical issue than an actual entropy issue. It may only be a matter of time before researchers find an LED with an efficiency of 160% which emits a wavelength of light that can be absorbed by a photovoltaic cell with an efficiency of 70%. If this were possible, it would essentially be a free energy source, able to convert ambient heat energy into electrical current.

Quite an interesting philosophical supposition.


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## argleargle (Feb 15, 2013)

I call shenanigans on 200% efficiency. This implies that the device is within a closed system; it is not. It requires ambient heat, correct? It therefore operates under a larger system than just the circuit of the device.

Thermodynamic law states that in a closed system, entropy must always increase (the lack of the ability of energy to do work.) Kind of like the Earth, we'd have big problems if it WERE a closed system... but it is not. It is powered externally by the Sun. Therefore, the Earth is not a "10,000% efficient power source." Likewise, this "200%" business is also misleading.

I'm playing kind of loose with terminology there, but I hope it is a halfway decent analogy. I think someone was just trying to explain this concept to a "normal person."

Also, "free energy devices," aka "perpetual motion machines" tend to get debunked in 5 minutes or less once you get your hands on one. Past history has shown that they have all been scams so far.

I would definitely lose my composure and giggle like a schoolgirl if someone managed to actually disprove conservation of matter and energy, or even F=ma. It'd be *GRAND!!!* Science fiction becomes reality, infinite batteries become possible, on and on...

 ...but nobody has managed to pull that one off yet after scientific scrutiny. There is a large difference between a new theory and established scientific law.

Thoughts, anyone?


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## TEEJ (Feb 15, 2013)

LOL

I had a parallel thought.

Run it at half power, and use the remaining power to provide the power to run it, and, well, you have a closed loop system that powers itself.


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## argleargle (Feb 15, 2013)

TEEJ said:


> Run it at half power, and use the remaining power to provide the power to run it, and, well, you have a closed loop system that powers itself.



Once your design is properly vetted, I'll take an array of 100,000 of them to power my house for free.


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## TEEJ (Feb 15, 2013)

I think its really saying that when you plug it in, its also getting power from heat, thus, cooling the room.

When you add the energy it gets from the room though, it explains where the extra out put comes from.


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## argleargle (Feb 15, 2013)

...and it replaces my air conditioning unit! :duh2:


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## TEEJ (Feb 15, 2013)

I'll replace my oven light, and use the oven to power the refrigerator.


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## argleargle (Feb 15, 2013)

Griswold Christmas roof, I am now a power station and a landmark for aircraft.


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## TEEJ (Feb 15, 2013)

OMG!

We can stop global warming!

:santa:

Install these where the heat from the sun will drive them at 200% efficiency, so for every watt the sun hits them with, they cool the earth by 2 watts.

Install them in the deserts and we can return them to jungle!


Install them on people, and they can both be brighter, and, cooler!


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## awenta (Feb 15, 2013)

LMAO. Teej just solved all the world's problems.


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## jtr1962 (Feb 15, 2013)

I'm actually more intrigued at the possibility that these can be developed into a more efficient solid-state heat pump than existing bismuth telluride thermoelectric modules. If they happen to emit a little light also, wonderful-you can light your refrigerator and cool it with the same device. If not, it doesn't really matter. I love the possibility of getting to cryogenic temperatures. That's well out of the range of standard thermoelectric modules which are hard pressed to get much under about 200K. I'd love to build a little insulated box which could get close to liquid nitrogen temps, or at least as cold as dry ice.


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## arek98 (Feb 15, 2013)

Interesting. Imagine multiemitter light. Mixed regular LEDs for heating and new once. Circuit that controls it. Regular LEDs are cooled boosting their efficiency and new ones convert otherwise wate heat into light. I would sayy combinet efficeincy may be pretty good and no problem cooling environment to much (where it is not intended)


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## awenta (Feb 17, 2013)

jtr1962 said:


> I'm actually more intrigued at the possibility that these can be developed into a more efficient solid-state heat pump than existing bismuth telluride thermoelectric modules. If they happen to emit a little light also, wonderful-you can light your refrigerator and cool it with the same device. If not, it doesn't really matter. I love the possibility of getting to cryogenic temperatures. That's well out of the range of standard thermoelectric modules which are hard pressed to get much under about 200K. I'd love to build a little insulated box which could get close to liquid nitrogen temps, or at least as cold as dry ice.




You can buy a box of liquid nitrogen.


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## Esko (Feb 19, 2013)

Some older threads with some links:

http://www.candlepowerforums.com/vb/showthread.php?334523-230-Efficient-LEDs
http://www.candlepowerforums.com/vb...D-converts-heat-into-light-efficiency-gt-200-!


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## Anders Hoveland (Feb 22, 2013)

argleargle said:


> I call shenanigans on 200% efficiency. This implies that the device is within a closed system; it is not. It requires ambient heat, correct?


It is still essentially 200% efficiency. The heat being consumed is ambient heat, without any temperature gradient. It is essentially free energy.



argleargle said:


> Thermodynamic law states that in a closed system, entropy must always increase (the lack of the ability of energy to do work.)


Except this "law" of thermodynamics is not actually a real law. It could potentially be broken, and there is nothing in fundamental physics which says this cannot happen. But so far it has never actually been clearly demonstrated. It is very challenging to try to turn the random order of tiny molecules into useful work energy, without some sort of temperature difference on a larger scale.



argleargle said:


> Also, "free energy devices," aka "perpetual motion machines" tend to get debunked in 5 minutes or less once you get your hands on one. Past history has shown that they have all been scams so far.
> 
> I would definitely lose my composure and giggle like a schoolgirl if someone managed to actually disprove conservation of matter and energy, or even F=ma. It'd be *GRAND!!!* Science fiction becomes reality, infinite batteries become possible, on and on...


A "free energy" machine is not necessarily the same thing as creating energy out of nothing. Some types of free energy machines attempt to convert some form of ambient energy, such as heat or "zero-point". Of course, a successful demonstration has never be done yet. That does not mean it is impossible, it may be beyond current technological reach. This LED phenomena offers a chance that such energy could be harnassed, although it is still not clear yet whether it is just a dead end.


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## argleargle (Feb 22, 2013)

Anders Hoveland said:


> Except this "law" of thermodynamics is not actually a real law. It could potentially be broken, and there is nothing in fundamental physics which says this cannot happen. But so far it has never actually been clearly demonstrated.
> 
> From:
> http://en.wikipedia.org/wiki/Second_law_of_thermodynamics
> ...


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## 2xTrinity (Feb 22, 2013)

Anders Hoveland said:


> It is still essentially 200% efficiency. The heat being consumed is ambient heat, without any temperature gradient. It is essentially free energy.



I read the paper. The device was only operating above-unity electrical efficiency when the substrate was heated to well above ambient. It was at 200% at 135C. When operated at room temperature, the substrate was cooling down but it was a net consumer of electrical power like you'd expect from a thermoelectric cooler. 

What's interseting however is that unlike simply creating a temperature gradient, or emitting photons due to blackbody radiation, this is emitting wavelengths that are much much shorter wavelength than would be expected from the temperature. At 135C a passive device is going to radiate mostly at ~10microns, but this device peaks at more like ~1-2 microns. 

This type of technology might be useful to extract useful energy from heat with small tempreature gradients. A huge heat source with small temp gradient might not be hot enough to drive a traditional engine, but a device like this might be able to create a small amount of high energy photons that can be absorbed efficiently with a photodetector and extract some net energy that way.


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## Anders Hoveland (Feb 22, 2013)

2xTrinity said:


> I read the paper. The device was only operating above-unity electrical efficiency when the substrate was heated to well above ambient. It was at 200% at 135C. When operated at room temperature, the substrate was cooling down but it was a net consumer of electrical power like you'd expect from a thermoelectric cooler.


True, but is does demonstrate the principle that ambient heat could potentially be harnessed. Yes, 135C is higher than room temperature, but still no temperature gradient is needed.



2xTrinity said:


> When operated at room temperature, the substrate was cooling down but it was a net consumer of electrical power like you'd expect from a thermoelectric cooler.


Except that the energy it radiated _could be _a more useful form than the heat energy it absorbed. If you can turn ambient heat into light, that is free energy. It doesn't matter if it consumes 1 watt of power, if 2 watts of power can be generated from converting the light back into electrical current.

However, this has not been verified, and it could very well be that there is some type of entropy consideration that may prevent more electrical energy from being extracted than what is being put in, when the maximum efficiency of the photovoltaic cell is factored in. Right now we just do not know. Since it is *ambient heat *there might not be any increase in entropy.



2xTrinity said:


> What's interseting however is that unlike simply creating a temperature gradient, or emitting photons due to blackbody radiation, this is emitting wavelengths that are much much shorter wavelength than would be expected from the temperature. At 135C a passive device is going to radiate mostly at ~10microns, but this device peaks at more like ~1-2 microns.


Nothing real surprising there. Incandescent photonic crystals have been found not to follow the law of blackbody radiation either.



2xTrinity said:


> This type of technology might be useful to extract useful energy from heat with small tempreature gradients.


But that's the thing: no temperature gradient is needed, only the presence of heat. This is what makes it so different from any other heat engine.




argleargle said:


> "The second law is an empirically validated postulate of thermodynamics"
> 
> Basically, "they have actual proof."


But it's still not a *fundamental* law of physics, meaning it could_ potentially _be violated. True, so far this has never been demonstrated, but being that it is really a statistical law, unlike many other simple phenomena, validating a violation would actually require the building of a complex device and quantitative measurements.

Yes, the second law is a proven observable phenomena, but does not necessarily imply that it will always hold under any conditions.




argleargle said:


> You speak of Maxwell's Demon.
> 
> Scroll down to "criticism and development." 2nd thermo isn't actually violated if you're taking energy from outside the system, hence an "open system." A closed system cannot do this. It's just a matter of definition of the scope of your system. Example: Your light bulb is powered by the electrical grid. By stating that the bulb itself is a closed system, you can draw a conclusion that isn't true.
> 
> As far as using a temperature difference on a larger scale to extract energy, this is how Stirling engines work. There's another thread open about those here at the moment.


Yes, it would still violate the second law. Entropy could be _*decreasing*_. It would be like transferring more heat from a cold area to a hot area, without venting out heat anywhere else.
Energy can be taken from outside the system, but is being concentrated here. Concentrated such that it would be an easy matter to return the energy to its original state.

Unfortunately, the concept of entropy is not really a mathematically precise one, so it can be difficult to quantify its existence it changes from one form of energy to another. Entropy is more of a statistical generalization.

A better analogy would be a heating unit which used cold air to heat the inside the house without consuming any energy itself. That is what we are talking about here. If you want to call it a heat pump, fine, but it is a "free energy heat" pump. Obviously there are huge implications if this is actually possible.

Look, entropy or not, it would be an amazing discovery if we could just set a device down and it would give out a continuous supply of electric power, without being constrained by the availability of sunlight. Any generator that can absorb ambient heat could effectively "suck" it all in from its surroundings. This is just not the case with harvesting sunlight by solar panel.


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## AnAppleSnail (Feb 22, 2013)

Well, that's what a heat pump does. It uses energy (Electricity) to move heat 'uphill.' Your house aircon probably does this, Anders. If you design your heat pump right, the 'heat' from its input energy also warms the side you'd like it to. Either way, you have a Coefficient of Performance, not an Efficiency.


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