MIT develops 200% efficient LED

[Chrontius]

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.

 

[Norm]

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

 

[awenta]

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

 

[slebans]

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)

 

[jtr1962]

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.

 

[Norm]

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

 

[AnAppleSnail]

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.

 

[bose301s]

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.

 

[Norm]

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

 

[Gregozedobe]

.... 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).

 

[AnAppleSnail]

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.

 

[2xTrinity]

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".

 

[Hooked on Fenix]

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.

 

[Anders Hoveland]

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.

 

[argleargle]

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?

 

[TEEJ]

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.

 

[argleargle]

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.

 

[TEEJ]

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.

 

[argleargle]

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

 

[TEEJ]

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