Comment by klyrs

> I think the part that isn't intuitive to everyone is how to "accumulate" potential energy if you don't have batteries/capacitors. Like how I can't fill my car tire with my bike pump. There's... there's magic missing.

As others have pointed out, you can! If you're rather patient. They've even got compatible valves!

And you can think of a pneumatic tire as a kind of battery -- potential energy is roughly the volume times the pressure differential.