Perptual Power

Perpetual motion doesn't even allow for energy to be harvested from the system while maintaining motion. That would require the system to be creating excess energy. Best you can do is make something not lose much over time with well oiled joints and put it in a vacuum. Sorry.

I think you mean 2 way hole.

magnetism and gravity would be the power we could harness until heat death.

but bare in mind that you'd have to supply the power harnessed to a system, not connected to the one you are harnessing from.

and that's where we are stuck.

Magnets don't float

>if we start cutting down trees for fuel, we'll fuck up the ecosystems!

I hope you're aware just how fucking much of the planet used to be forested, before we came along and started building villages, ships and mines. Entire countries have been basically stripped bare. Many of the "iconic" countrysides of today, like Greece's rocky landscapes, used to be green, and it has caused widespread extinctions and erosion. It's not "fine".

If we took the energy from the earths motion relative to the sun, the earth would slow down relative to the sun, since we are removing kinetic energy to use it wherever.
Do you think that it a good idea? Even so, how excactly would you go about it?
Also I'm pretty sure solar energy is a better example of what you're looking for.

>possibly disrupting ecosystems or causing large chains of events we cant predict?

we can accurately predict just about everything on our planet. the climate scientists said so.

They've been known to...

I mean not like in the schematic shown

Water under the "one-way hole" (a valve?) will not be able to make its way into the container of mercury, because mercury is denser than water. If you provide energy to force it through, to the point where it will float to the top, this energy will exceed the energy captured from water overflowing the container.
This is not a new idea.