Tesla was right...

 ...you can pull electricity out of the air. Of course, he was wrong as to how.

So, apparently, you can actually use certain materials to generate clouds. And clouds can produce large amounts of electricity. We've all seen that. It's called lightning.

A thin layer of material designed with very tiny micropores would create a charge imbalance, like that in a cloud, creating a battery that operates as long as there's humidity in the air.

It wouldn't work everywhere. Las Vegas would have problems. Florida would, though, do just fine.

As would many parts of the global south where this would be particularly valuable...

Of course, it's on paper right now. It hasn't been demonstrated in the real world yet.