Fossil fuel would I guess be chemically stored fusion energy from a long time ago
I could be wrong, but I think geothermal may be the (sole?) exception to that. That heat is from the formation of the planet and radioactive decay (fission). That heat/energy would have coalesced during the accretion process regardless of whether the sun was adding energy. Again, I think. If I’m wrong, please enlighten as this is an interesting topic.
Edit: I was thinking I might be technically wrong since we can’t really “renew” geothermal energy, but Wikipedia does have it classified as renewable:
Geothermal power is considered to be a sustainable, renewable source of energy because the heat extraction is small compared with the Earth’s heat content.
Radioactive elements were formed in the last moments of a collapsing star, so even those were formed during fusion.
That is true. I guess it depends on how much of the heat is generated via fission processes and how much is just stored from planetary accretion. I don’t have any numbers for that at this moment, but I will certainly concede that geothermal is fusion-assisted lol.
Maybe tidal energy would also be an exception? It’s from the motion of the moon, which is the result of ancient planetary collisions?
How does wind energy fit then?
Or hydro electric dams?
Wind: The sun (a giant fusion reactor) heats the atmosphere which generates the wind (highly simplified).
Hydro: Driven by the water cycle where the sun plays a key role in the “evaporation, condensation, precipitation” process.
