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  1. #1
    Flashaholic* Mattaus's Avatar
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    Default 230% Efficient LEDs

    ***Apologies if this does not belong in this section of the forums, or if this is repeated news. I searched and could not find it posted previously.***

    So some interesting news taken from Gizmodo but I saw it elsewhere yesterday:

    Light bulbs have always required more electricity than they need to produce light because the energy conversion process — changing electricity to light — was inefficient. But an MIT research team has just shown that an LED can actually give off more light than it consumes in electricity.
    Incandescent bulbs are the poster child of inefficient energy conversion. The devices heated a filament with an electrical current which not only produced light, but a lot of waste heat as well. Fluorescent bulbs, CFLs and even conventional LEDs all generate the same waste heat to varying (albeit much smaller) degrees but none has ever reached 100 per cent efficiency — a mark known as “unity efficiency”.


    The team from MIT posited that while the bulbs energy requirements decrease at an exponential rate (halving the voltage reduces the input power by a factor of four), the lumen output would decrease linearly (halve the voltage and the lumens drop by half as well). This means that at some point, the amount of lumens the bulb is emitting would be more than the amount of energy spent — essentially “free” light.


    Granted, this point occurs only when using minuscule amounts of electricity to power incredibly dim bulbs. In their experiments, the team was able to generate 69 picowatts of light from just 30 picowatts of energy. They did so by harnessing waste heat, which is caused by vibrations in the bulb’s atomic lattice, to compensate for the losses in electrical power. The device also reacts to ambient heat in the room to increase its efficiency and power the bulb.

    This process cools the bulb slightly and could eventually be employed to manufacture “cold” bulbs that don’t generate any heat, only light. And, since the same physical mechanism from these tiny bulbs can be applied to any LED, they likely will be. Original Source via Physics.
    One day it will hopefully be a bit brighter

    - Matt

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    Flashaholic* mvyrmnd's Avatar
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    Default Re: 230% Efficient LEDs

    So if we run 100 billion XP-G's at 30 picowatts a piece, we'd be getting 6.9W of light for 3W of electricity. I think. That many zeros messes with my brain.

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    Flashaholic* monkeyboy's Avatar
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    Default Re: 230% Efficient LEDs

    Quote Originally Posted by mvyrmnd View Post
    So if we run 100 billion XP-G's at 30 picowatts a piece, we'd be getting 6.9W of light for 3W of electricity. I think. That many zeros messes with my brain.
    Interesting idea. Back-of-the-envelope calculation:

    You'd need an area of 1.5 km x 1.5 km and more money than Bill Gates. Not sure you'd even be able to see a dim glow with 6.9W spread over that area. Imagine the cabling you would need and the power losses through that length of cabling!

    How about this for an idea: put the die in contact with an efficient photovoltaic solar cell which simultaneously powers the die and extracts energy from it, and you have a machine that extracts heat from the environment and directly produces electricity. I'm sure that violates every law of thermodynamics though.

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    Flashaholic* uk_caver's Avatar
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    Default Re: 230% Efficient LEDs

    Quote Originally Posted by monkeyboy View Post
    You'd need an area of 1.5 km x 1.5 km and more money than Bill Gates. Not sure you'd even be able to see a dim glow with 6.9W spread over that area. Imagine the cabling you would need and the power losses through that length of cabling!
    If starlight is ~10^-4 lux(10^-4lm/m^2), with white light at ~350lm/W the 6.9W of light would be 2400lm, spread over the 1.5x1.5km, about 10x as bright as starlight, if I haven't screwed up calculations.

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    Default Re: 230% Efficient LEDs

    Quote Originally Posted by uk_caver View Post
    If starlight is ~10^-4 lux(10^-4lm/m^2), with white light at ~350lm/W the 6.9W of light would be 2400lm, spread over the 1.5x1.5km, about 10x as bright as starlight, if I haven't screwed up calculations.
    You are assuming that ALL of the stars combined in the night sky are covering the ground with a given Lux

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    Flashaholic* uk_caver's Avatar
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    Default Re: 230% Efficient LEDs

    Quote Originally Posted by TEEJ View Post
    You are assuming that ALL of the stars combined in the night sky are covering the ground with a given Lux
    Well, I was using generally given figures for illumination by starlight (presumably on a fully clear moonless night away from any artificial light), and I was assuming the figures I was progressing from were correct.
    As far as the LEDs were concerned, the assumptions I was making included:
    a) the output being visible light
    b) a rough watt - lumen/lux conversion of about half the green optimum
    c) a basically infinite illuminator, such as extensive LED-covered panels slung overhead much wider than they were high above me, such that the intensity of light hitting the ground was the same as the intensity of light leaving the emitting panels (so definitely nothing like a flashlight actually lighting an area much larger than its emitter to starlight-like levels).

    The first one of which may be wrong, the second inaccurate, and the third impractical (though putting some kind of upper bound on the possible intensities of illumination)

    Though it was only an estimate to get some rough handle on the kind of light/energy levels involved.

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    *Flashaholic* precisionworks's Avatar
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    Default Re: 230% Efficient LEDs

    the team was able to generate 69 picowatts of light
    69 X ( 10-12 ) watts. Or .000000000069 watts.
    Surefire® boring including E-Series & Weapon Lights, gun repairs, blueing & custom work * PM's disabled * Please Email & PayPal through PrecisionWorks.co

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    Default Re: 230% Efficient LEDs

    If the extra energy comes from the thermal energy in the bulb (waste or from its surroundings), I can see this going well in warm countries. People in colder climates will to turn up their heaters a bit more though...
    Finning does help dissipate heat. This is why the fins are removed before cooking fish. Otherwise it will throw off the heat and not reach the proper cooking temperature. --Duglite

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    Flashaholic* Mattaus's Avatar
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    Default Re: 230% Efficient LEDs

    Quote Originally Posted by Th232 View Post
    If the extra energy comes from the thermal energy in the bulb (waste or from its surroundings), I can see this going well in warm countries. People in colder climates will to turn up their heaters a bit more though...
    So what you're saying is that we'll be right here in (mostly) sunny Australia.

    It's a step in the right direction at least. The speed at which most things are advancing is insane these days, and just about the only thing that is not moving as fast as everything else is batteries. So we need to get more efficientl, though it wouldn't harm anyone if both improved hand in hand.

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    *Flashaholic* StarHalo's Avatar
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    Default Re: 230% Efficient LEDs

    I wonder if 69 picowatt emitters would work in night vision display equipment..

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    Default Re: 230% Efficient LEDs

    Quote Originally Posted by Mattaus View Post
    It's a step in the right direction at least. The speed at which most things are advancing is insane these days, and just about the only thing that is not moving as fast as everything else is batteries. So we need to get more efficientl, though it wouldn't harm anyone if both improved hand in hand.
    You just made me realise something. My titanium lights with their lower thermal conductivity will perform better than my Al lights, which will take away all that valuable heat from the LED and waste it heating the surrounding air. That would be really funny to see.
    Finning does help dissipate heat. This is why the fins are removed before cooking fish. Otherwise it will throw off the heat and not reach the proper cooking temperature. --Duglite

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    Default Re: 230% Efficient LEDs

    So does that mean we should throw away our heatsinks?

    Not sure how they "harness" the waste heat; maybe uber-micro stirling engines?

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    Flashaholic* Mattaus's Avatar
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    Default Re: 230% Efficient LEDs

    Quote Originally Posted by Th232 View Post
    You just made me realise something. My titanium lights with their lower thermal conductivity will perform better than my Al lights, which will take away all that valuable heat from the LED and waste it heating the surrounding air. That would be really funny to see.
    Actually the heat sinking practices we currently all strive to implement would become null and void...flashlight design would/could change dramatically. I am of course only thinking about flashlight applications here. I'm sure there are many more far reaching implications.

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    Flashaholic* mvyrmnd's Avatar
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    Quote Originally Posted by monkeyboy View Post

    How about this for an idea: put the die in contact with an efficient photovoltaic solar cell which simultaneously powers the die and extracts energy from it, and you have a machine that extracts heat from the environment and directly produces electricity. I'm sure that violates every law of thermodynamics though.
    It would only break the rules if it ran forever. With no external input of power after the initial power up, it would simply fade out over time.

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