In short, Tesla's energy transmission system uses ground surface as a "wire" by means of which it is possible to transmit electric energy to the large distances. An idea of using the Earth as a conductor is not new as such.
In the very beginning of the era of electrical engineering, the Earth was actively used as a second wire (direct current was transmitted to the consumer via one wire while the ground was used as a second wire so that the current could return back to the power source). However, transmission of considerable amount of an electrical energy through Earth to the large distances and with high efficiency factor value is possible only by means of Tesla Tower due to coupling of resonance circuits, that is, Tesla Towers. And all of that does not cause any environmental harm.
In a broad sense, two Tesla Towers work in the following way. Imagine simple wire with the metal balls located in the both ends of it (the balls serve as the charge integrators, or as the capacities so to speak). That is, we can arrange alternating charging of the ball-the charge integrator or sort of pump in and out the electrons from the wire into the ball. In this case, the current is going to flow across the wire, reach its other end and evoke similar alternating charging of the second charge integrator. Take a look at the example of corresponding setup as shown below.
Such simplest experiment allows to understand the main working principle of the system consisting of two Tesla Towers (in this case the Earth surface serves as a wire and the Towers itself are serving as balls-the charge integrators). The Tower-Transmitter creates alternating charge on its integrator. It evokes the currents in the ground around the Tower, which scatter away from the Tower. Next, these currents make the second Tower-Receiver resonating and this allows to get an energy from such receiver. Following such scheme, Tesla itself conducted his early experiments on single-wire energy transmission.
In simple words, energy transmission happens in a same way as in the usual transmission lines, that is, via wire. The only difference is that it requires one wire instead of two. Superficial layer of the Earth with depth of about 100 to 1000m (together with Earth-Ionosphere waveguide) acts as such wire. The Tower-Transmitter literally "oscillates" the currents flowing across the Earth ground to different sides away from the Tower and the Tower-Receiver "collects" the energy from these currents. It happens exactly likewise it is shown in picture below, where "the wire from water" is used instead of "the wire from ground" as the water is well known for its good conductivity (the picture is taken from the website indicated above).
Current waves' propagation in "the wire from ground" via very large distances is possible. At that, energy attenuation in such wave is very small due to small resistance of the ground surface (and due to very large sectional area of such conductor) as well as the presence of so-called Earth-Ionosphere waveguide and considerable spacious charge in the lowest atmospheric levels (which decrease the energy losses to the emission created by the alternating current in the ground).
It would be impossible to transmit the energy with good efficiency factor value if the energy would be just "pumped" into the planetary resonance, that is, to the current waves in the wire-ground of the Earth and would be sort of "taken away" in some other place. Energy amount would quickly decrease as the distance from the Tower-Transmitter would grow like it happens, for instance, during working process of the convential antennas. So, receiver could get only very tiny amount of energy.
Fortunately, in our case, the energy is propagating not like conventional radio waves do, that is, not in all directions, but via singe-wire transmission line (i.e., via wire consisting from ground surface). Both transmitter and receiver function in similar way, and receiver creates the current waves flowing away via ground. So receiver creates similar current waves flowing away from the receiver. Such "secondary" wave (in case of certain location of both transmitter and receiver) acts upon transmitter changing transmitter's impedance, and forces the transmitter to give greater amount of energy to the currents in ground. In that way, so-called coupling of resonance circuits takes a start. As a result, the Tower-Receiver cannot be considered as a passive setup. In opposite, it strongly acts upon the Tower-Transmitter. And that allows to get high value of the efficiency factor of energy transmission.
Project Witricity can serve as an excellent example of using the coupled resonance circuits as it allows to arrange wireless energy transmission with high efficiency factor value exactly based on the principle of the resonance-coupled circuits:
So in a broad sense Tesla's Tower is a global analog of Witricity, and the WiTricity technology is similar to the idea of our experiment. WiTricity employs near field resonant inductive coupling of two resonant circuits to achieve a high power-transmission efficiency. The scope of our approach is practically same. However, there is no distance limitation like in case of WiTricity due to usage of single-wire transmission line (the Earth, i.e. ground wave and earth-ionosphere waveguide) for the transmission of an energy by conventional currents.
As the issue is about the currents flowing in the thick layers of the Earth ground, the certain questions may arise concerning the safety of such energy transmission method. Fortunately, as the current is distributed over the large section of such single-wire transmission line (ground surface), current value is so small in any certain place that can be hardly detected and such small current density does not affect any kind of processes or any live substances. That is, the current values in such system will be much smaller than those of the vertical currents that are constantly flowing between ground and ionosphere (and in which every organism is safely living). The only place, where the current values reach great numbers, is located in the immediate surrounding of the Tower to which the human access should be certainly restricted.
It is certain that everything described above is just an attempt of describing the main working principle of the Tower in extremely simple terms and without complicating it with some important details. More detailed description of such principle can be found in the article called as "Examining Working Principle of Tesla Tower".
What is the Tesla Tower NOT about: