Nuclear fusion
Possible energy source - not viable yet.
Energy inputs
Takes more energy than it produces. EROI is still below 1.
Every once and awhile, there are "major breakthroughs" in nuclear fusion (the last being in December 2022), and misleading news articles are quick to make it look as though scientists have finally achieved a "net energy gain". However, it's only a net gain relative to some of the energy inputs, not the whole system in total. In other words, fusion is not a viable power source yet. We don't know how long it will take to be. Since climate change is already near a tipping point, we need to explore other solutions besides fusion only.
Scarcity of fuels
There are no viable reactors yet, but of the prototypes so far, some rely on tritium, an extremely rare form of hydrogen. Supply would be an issue.
Other possible fuels include deuterium, lithium or boron, which are comparatively less rare. In any case, only small amounts of the fuel would be needed to produce large amounts of energy.[QUANTIFICATION needed]
Ideally, fusion reactors could rely on ordinary hydrogen, which would be abundant enough to last hundreds of millions of years.[QUANTIFICATION needed]
For now, all of this is hypothetical - regardless of fuel, no prototype so far has been able to produce more energy than it takes to run it.
See also
- Nuclear fission (not fusion)