edit: I really don't know much about Nikola Tesla's wireless transmission idea, and can't say if what I wrote in this post is true. I can say for sure the effect must be there, but not how dominant it is. might be negligable.
The atmosphere is packed with hydrogen ions, as has been suggested by Gerald Pollack in his 2013 book. This fact has not been widely known, it makes sense if one studies Pollacks 2009 experiment that proves the actual mechanism behind osmosis. This means that the atmosphere has the conditions to act as both poles of a battery, it can store electrons, in water where the oxygen stores 2 extra electrons, and it can release electrons, in O2. This chemical balance is the basis of many mechanisms in biology that have yet to be understood (I have documented many. )
The top capacities in Wyrdenclyffe that were assumed to act by capacitance, storing electricity, actually act by providing the surface area for electrochemical reactions that "store" the electricity in the same way a battery does. They are not capacitor plates, they are electrochemical cells.
This means that they have a much greater "storage" potential than assumed, since they are not what store the charges, the atmosphere itself is.
The chemical reactions are simply 4 H+ + 4 e- + O2 <=> 2 H2O, reversible. It can accept alternating current easily. It also accepts direct current, as you see here -->