Get your energy from the small sources – build permanent energy sources into your system.
In the new paradigm of telecosm ubiquitous energy will be needed – many times in small amounts. This can be arranged by utilizing the energy that is already there: excess heat, heat flows, pressure, vibrations, water flows, wind or air streams, radio waves.
The sources are there – put in a suitable device and you have permanent power. No need to supply batteries!
And there is more to it: Humans move around – extract energy from the motion of humans through public spaces, responsive sub-flooring systems made up of blocks that depress, the bounce in a bridge, self-winding watches we all know, self-energizing implantable medical micro systems (SIMMs), and many more…
Some of these ideas are good – parasitic energy has a future when well used.