Thank you for your comment. I was talking about "purposely" added capacitance.
Actually, I had forgotten to post this picture:
According that, in an AC circuit, a capacitance (and/or a coil) does not consume (and produce) nothing.
Notably: take a "tank circuit" (parallel resonance).
Seen from the source, it has an huge impedance. It behaves like an almost open circuit.
So, very few power is consumed from the source.
But, in this tank circuit, amperes are circulating.
Unfortunately, these amperes are considered as useless.
Fortunately, some witty guys (not me!) had the idea of designing non conventional caps and coil.
Actually, a kinda mix of cap and coils.
One question is: does Nature care (NRG-wise) whether or not a tank circuit is made of "normal"
caps and coils or tricky (non-conventional) ones? Seems not.
Another question is: does the AC Source will figure out (and react (Lenz law)) if
we try to get some power from a non-conventional tank circuit?
Usually, trying to get back some power from a "normal" resonating tank circuit
(with a secondary coil, for ex) leads to break his resonance and the efficiency is < 1.
Now, can we (without a secondary coil, for ex) get back some free power?
Could we cheat the source?
I have not the answer. I came across these issues reading Valdimir Utkin.
I have to make some experiments.