4 ms·

Unfortunately this (truly 100%) is impossible ipso facto the 2nd law of thermodynamics.

Nomentatus 10y ago
This rules out superconductors, does it not?
35bge57dtjku 10y ago
Please explain how this is. It seems like something could convert all energy to light without generating heat and while conserving total energy & mass...
- contravariant 10y ago
  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.
ehsanu1 10y ago
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..
- Feuilles_Mortes 10y ago
  Hm clearly I've got some more learning to do about this. Thanks!
legulere 10y ago
In fact because of thermodynamics over 100% efficient LEDs are possible. This was practically demonstrated some years ago: https://phys.org/news/2012-03-efficiency.html https://phys.org/news/2012-03-efficiency.html Converting light to electricity on the other hand cannot reach 100% efficiency.
- ejolto 10y ago
  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] [1] Fig 1 (a) https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.108.097403 https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.108.097...
  - contravariant 10y ago
    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.

This rules out superconductors, does it not?

Please explain how this is. It seems like something could convert all energy to light without generating heat and while conserving total energy & mass...

contravariant 10y ago
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.

ehsanu1 10y ago

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..

Feuilles_Mortes 10y ago
Hm clearly I've got some more learning to do about this. Thanks!

legulere 10y ago

In fact because of thermodynamics over 100% efficient LEDs are possible. This was practically demonstrated some years ago: https://phys.org/news/2012-03-efficiency.html https://phys.org/news/2012-03-efficiency.html Converting light to electricity on the other hand cannot reach 100% efficiency.

ejolto 10y ago
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] [1] Fig 1 (a) https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.108.097403 https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.108.097...
- contravariant 10y ago
  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.