That circuit is overly complicated, and thus, burns most of the energy input in losses from the much too many unneeded components.
The following is the much simpler circuit of a crystal radio, which makes you hear AM radio from the nearby station, without a battery.
simulate this circuit – Schematic created using CircuitLab
It's so well-known it even was on Hal Roach’s Rascals and a gimmick in some comic magazine
Well, how does this work? Energy is taken from the EM field, rectified/demodulated by the low drop, soft I/U characteristic, hence Germanium, diode, then fed into the high-ohms earphones. Coil and capacitator are only there for selection of a specific station. When you leave them out, you hear AM-Babble.
And that's what your circuit does. It leaves out the frequency selection, feeding all received energy to the consuming circuit on the right. The capacitators and diodes indeed work as a voltage doubler, but that's nonsense because they have so much loss you are better without them.