[short_sells_poo]

You could also say we are already using fusion power - via solar panels. We have a massive ball of plasma powered by fusion in the sky and we are harvesting the energy it creates at an ever growing scale.

Whether we'll be able to replicate it profitably at small scale is a question.

[fluoridation]

Of course, by that definition all forms of power generation are fusion, more or less removed from the fusion reactor in question.

[zeroonetwothree]

Some part of geothermal energy comes from gravity which could be argued is not related to fusion (even if the matter undergoing gravity was created in fusion)

[fluoridation]

Geothermal energy is derived from differences in kinetic energy between different layers of the planet (so extracting it saps kinetic energy from the planet's rotation). The energy stored in the Earth's rotation comes from the kinetic energy in the Solar nebula, which itself comes from stellar explosions in the primordial universe, which themselves were caused by fusion.

[evandrofisico]

following that definition even fossil fuels would be based on fusion, as most of it is comprised of photosynthetic life forms.