What does 100% efficiency mean? Does that mean that for some power delivered to the LED load there is a (near) 100% efficient conversion to visible light ("photons")? Would that mean the LEDs operate with practically no heat generation?
And yet you won't find any shortage of people who will call you a terrible, terrible naysaying pessimist if you dare to voice the prediction that an efficiency jump like from incandescents to CFL or from CFL to LED won't ever happen on top of state of the art LED.
Oh, that is nicely misleading. The combination of being totally awed by the close proximity to perfection implied by the misreading and being used all of SI fitting together like Legos completely got me (see downvoted comment below, I guess the yaysayers could be right once more - and even now I still think that a photon stream worth one Watt of power, constrained to the visual spectrum could be a very nice alternative unit for the value usually given in lumens).
Please explain how this is. It seems like something could convert all energy to light without generating heat and while conserving total energy & mass...
Well, the law they're referring to states that rather than just conserving energy and mass you also can't have a process that lowers entropy. Although it's unclear how this is relevant because, if anything, converting kinetic energy to light increases entropy, or at the very least doesn't decrease it.
You're probably thinking of heat engines. Extracting 100% efficiency from a heat source is impossible. That doesn't mean that near-100% of non-heat energy can't be converted to another energy type. Eg resistors pretty much convert electricity to heat at a 100% "efficiency" rate..
It needs to be pointed out that the diode isn't converting over 100% of the electrical power into optical power. The extra optical power comes from Peltier heat drawn from the semiconductor lattice. The LEDs only had ">100% efficiency" when heated to 135°C. At 25°C the electrical efficiency was less than 1%.[1]
That still counts. Ambient temperature and pressure are necessary for just about any 'engine'. In fact, extracting heat from the environment to do something useful is more impressive than just converting one form of energy into another.
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[ 6.3 ms ] story [ 41.8 ms ] threadhttps://c1cleantechnicacom-wpengine.netdna-ssl.com/files/201...
Converting light to electricity on the other hand cannot reach 100% efficiency.
[1] Fig 1 (a) https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.108.097...