Here's a truly alternative energy source: Drinking-bird-enabled triboelectric hydrovoltaic generator

I came across this article that seem really whimsical and silly, but it appears to be a legitimate way to general low amounts of energy that "converts evaporation energy into kinetic motion" as the scientific article states.

Here's the link to the published article:
Drinking-bird-enabled triboelectric hydrovoltaic generator

While you won't be powering your house from this or similar devices, I could see something derived from it powering sensors in the field, especially if the energy is stored in a capacitor for later use.

Here's an article at "New Atlas" that summarizes the above link and gives a less-technical description:
High-level description of the drinking-bird-enabled triboelectric hydrovoltaic generator

If any of you have a drinking bird toy, you could try creating your own generator that only uses water as the consumable fuel!

Yep minute energy...   for a sensor should work..

This makes me wonder how long one could keep this going  in a vacuum.