Just came up with this one! There will be some gaps in this plan, which is why I need your *delete me* So as I understand it, if you apply voltage to a piezoelectric crystal (henceforce refered to as PC), then mechanical movement will happen. The PC will bend. If you bend the PC, then a voltage is produced. Neat. So what if you had an automagic way to wiggle the PC around and create a constant, pulsed current?
If I remember correctly, quartz is paramagnetic. To me that means it can be made to be magnetic by sitting really close to a strong magnetic field. Won't be a strong magnet by any means. So lets say you had a really strong rare earth magnet just sitting next to a sheet of quartz. Like in the middle of the sheet. With induced magnetism, will the PC bend towards the magnet? If its bending, then logically it should produce a voltage! Capture that and store the output in a battery or capacitor or something.
A question about the PC: if it is bent and produces a voltage... does it have to be straightened out again before you can make it produce more voltage? So what if you had another strong magnet sitting on the opposite end, but two of them so it looks like the PC is in the middle of a triangle. It would act like a magnetic spring. The idea is to have the PC vibrate back and forth like crazy. The stronger central magnet bends it one way, and the 2 other magnets bend it back to normal shape. Constant vibration means its constantly moving meaning its constantly producing electricity.
Plausable?