Using operational amplifiers of the time, we found this circuit in documentation from the 90s. The configuration can be adapted to use modern operational amplifiers.
This circuit oscillates in the fifth harmonic of the crystal frequency. The circuit is from a 90's...
The output voltage is adjusted by the trimpot. The power transistor mist be mounted on a heatsink. The 3.9...
Among the alternative energy sources, one of the most promising is that represented by Astro-Rei....