You can even buy a small solar panel for ~$10 with positive and negative leads you solder; and power something like a Pi Pico^ directly. It kinda feels like magic.

^Not recommended literally due to brownouts/etc, but a cheap power management IC on a breadboard can solve that. Alternatively, add a battery/etc.

Home solar panels and batteries are just like this except on a bigger scale; and with (hopefully) more QC.