Solar power, geothermal power, hydro power, are effectively perpetual motion, for our purposes. Heat pumps kind of violate the "you can't get something for nothing" principle too, since you can get >100% return on the electricity you put into them. 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.
There's no thermodynamic reason you couldn't have a small device on your desk that uses ambient heat, moisture, light, etc to store energy that you can use to do work, just engineering and chemical reasons it's hard to do this on a scale that's relevant. https://en.wikipedia.org/wiki/Crookes_radiometer is over 100 years old and, if kept in sunlight, can provide "perpetual motion" for "free".
> 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.