Well if you ask me it is possible to make a pseudo perpertual motion device very easily.
When i say pseudo - i mean endless energy for all human timeframes.
1. A solar sail "mill" where half the wheel is in shade should be able to be pushed around.
2. A pendulum hanging from a very high structure should be able to wobble in counter tact with the earths wobbling..
3. And, of course, waveenergy
But there are many possibilities..
I suppose we humans have too large needs and better solutions than to use these..
The real problem with perpertual motion, i guess, is that the earth will only exist for a brief period compared to what we would guess the universe would do in comparison.. So just forget about worrying about solutions that should work more than a few 100.000 years and you will save yourself a lot of needless worrying.

"If democracy is the least bad form of government - then why dont we try it for real?"