[thaumasiotes]

> The laws of thermodynamics apply in closed systems, and our planet is not a closed system.

> Solar power, geothermal power, hydro power, are effectively perpetual motion, for our purposes.

I get solar power and hydro [also solar] power, but isn't geothermal power a closed part of the system? Where does solar input feature in that?

> The more we look into renewables, the more we can find ways to "cheat" by using "preprocessed" goods where the sun or the earth already did the hard part for us.

This is also a closed part of the system. If the argument you're making is "the planet is not a closed system", then you need to be using energy that comes from outside, not energy that is already contained in the system.

[BobaFloutist]

The sun is arguably ultimately responsible for geothermal. Even if geothermal is part of the closed system, it's still functionally perpetual motion for our purposes. The main argument I'm making is that perpetual motion* is, for all practical purposes, possible, as long as you're willing to be specific, and you're unconcerned with the heat death of the universe (none of us should be concerned with the heat death of the universe).