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Nuclear fusion reaction releases almost twice the energy put in
(www.newscientist.com)
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this post was submitted on 06 Feb 2024
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From another article: "In an experiment on 5 December, the lab’s National Ignition Facility (NIF) fusion reactor generated a power output of 3.15 megajoules from a laser power output of 2.05 megajoules – a gain of around 150 per cent. However, this is far outweighed by the roughly 300 megajoules drawn from the electrical grid to power the lasers in the first place."
https://www.newscientist.com/article/2350965-nuclear-fusion-researchers-have-achieved-historic-energy-milestone/
That's worded strangely (powering the lasers takes both 300 and 2.05 megajoules?) but oof
Powering the laser takes 300 MJ but the actual laser power (the energy in the light) is only 2.05 MJ. The rest of the energy is lost to heat and other inefficiencies. If the laser could be created with 100% efficiency then the input energy would also be 2.05 MJ.
Energy can be measured as occurring in different physical phenomena. There is energy in sound waves/packets, energy in light waves/packets, energy in matter, etc.
The 300 MJ number refers to the electrical energy in the form of electromagnetic fields carried specifically through solid conductors via electron movement along the conductors.
The 2.05 MJ number refers to the radiative energy in the form of electromagnetic fields sent specifically through free space/a vacuum (I presume; I didn't read the article, so maybe the laser medium was a vacuum or something else) via photons/waves. No electrons, aside from those in the lasers that create the photons in the first place.
So there is a conversion from electric to radiative energy here.
Start Edit:
And as another commenter said, in this conversion there are losses because materials aren't perfect.
:End Edit
If the 3 MJ radiant energy from the nuclear material was then converted back into electric energy via steam processes, we'd get a comparable number compared to the 300 one.
This is also why you see nuclear/CSP plants quoted in MWt and MWe: there is a conversion that takes place from thermal energy (vibrations of atoms/compounds) into electric energy.