Safe Realistic Flow Battery

Those are facts, but stating 'everything is really nuclear energy' obscures the point of the current thread, looking at methods of energy generation/storage, where 'energy' refers to 'usable electricity,' and we only look back one step for the energy source, to determine environmental impact.

Coal/wood/oil/gas are burned to release their stored energy as heat, and each produce byproducts from the combustion, and/or release other materials that were 'sequestered' in them, such as burning coal releasing radon gas (if memory serves). The head from the combustion is used to run turbines to generate electricity.

'Nuclear power' as used in terrestrial energy generation, refers to using the 'waste heat' from radioactive decay to run the turbines.

Geothermal uses the heat differential within the planet's crust for energy. This internal heat is not just from radioactive decay, but also from friction forces (continental drift, etc) and the residual heat from the planet's formation.

Wind Power is not only from the 'heat engine' in the atmosphere, but also from the diferential speeds of the air, as higher layers rotate slower than the lower layers, or the surface of the planet.

Tidal power comes mainly from the gravatational interaction between the earth and Moon, and not from the 'heat engine' in the oceans.

There are side effects of using every energy source, for example, pulling energy out of the tides will affect the balance between the earth and moon, although, even if we were to extract 100% of the tidal energy from the oceans, it would be like pulling a single snowflake from Mount Everest: The latter is not diminished in any measurable way from the removal.

And this offshoot is going SO FAR off topic with this discussion about what is, in essesne, splitting hairs, that I'm going to stop right here.