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Page 1-2 (Naoki Shinohara: Wireless Power Transfer via Radiowaves)

During the same period, when Marchese G. Marconi and Reginald Fessenden pioneered communication via radiowaves, Nicola Tesla suggested the idea of wireless power transfer and carried out the first WPT experiments in 1899 [TES 04a, TES 04b]. He said “This energy will be collected all over the globe preferably in small amounts ranging from a fraction of one to a few horse-power. One of its chief uses will be the illumination of isolated homes”. Tesla actually built a gigantic coil that was connected to a 200 ft high mast with a 3 ft diameter ball at its top. The device was called the “Tesla Tower” (Figure 1.1). Tesla fed 300 kw of power to the coil that resonated at a frequency of 150 kHz. The radio frequency (RF) potential at the top sphere reached 100 MV. Unfortunately, the experiment failed because the transmitted power was diffused in all directions using 150 kHz radiowaves, whose wavelength was 21 km. After this first WPT trial, the history of radiowaves has been dominated by wireless communications and remote sensing.

What does radio frequency potential mean here?

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Potential means "voltage relative to ground" so they had RF AC voltages of 100 MV relative to the ground / earth potential which is defined as 0 V (zero Volt).

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  • \$\begingroup\$ Thanks. Do you happen to know any article on the Internet which describes the theory behind working of the Tesla tower well? (And contains illustrations if possible...) \$\endgroup\$ – user133614 Sep 18 '17 at 19:42
  • \$\begingroup\$ Hmm, well that Tesla tower never worked as Tesla intended. He wanted to distribute electric power worldwide with that tower but never succeeded. In my opinion he wanted the impossible! But the tower itself is, I think, just a gigantic Tesla coil, see here: en.wikipedia.org/wiki/Tesla_coil for what that is. In my view, a Tesla coil is basically an LC resonator combined with a transformer and spark gaps to make abrupt current changes. This in turn can generate high voltages. \$\endgroup\$ – Bimpelrekkie Sep 18 '17 at 19:46
  • \$\begingroup\$ Personally I think the inventions of Tesla regarding polyphase AC power distribution and AC motors is much more practical and proves that he was indeed a genius. Yep, Tesla coils look more impressive but what purpose do they serve ? And how do we distribute mains power these days? Yes, AC. Thanks to Tesla! \$\endgroup\$ – Bimpelrekkie Sep 18 '17 at 19:51
  • \$\begingroup\$ Some amount of power can be captured from the reactive nearfield of Teslas resonator. That works fine as long as the loading is so low that sinusoidal oscillations do not get choked due too high losses. Teslas big tower unfortunately had a size of a proper antenna which of course was too much loading. \$\endgroup\$ – user287001 Sep 18 '17 at 20:06
  • \$\begingroup\$ Tesla built a Wardenclyffe Tower which never operated, because of the lack of money, then destroyed by US government because it was a good orientation point for the U-boot. Tesla stated that any of his inventions worked, so no doubt that also Wardenclyffe Tower would work. He never made an apparatus "by the way", without a deep math. and physical knowledge . He was genius, indeed. His brain was a complex computer, this fact was known to his professors at university, so they were abusing him for their math. calculations. \$\endgroup\$ – Marko Buršič Sep 18 '17 at 20:44

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