THE WIRELESS TRANSMISSION OF ELECTRICAL ENERGY

Introduction:
    It is possible that Nikola Tesla is best known for his remarkable statements regarding the wireless transmission of electrical power. His first efforts towards this end started in 1891 and were intended to simply "disturb the electrical equilibrium in the nearby portions of the earth... to bring into operation in any way some instrument." In other words the object of his experiments was simply to produce effects locally and detect them at a distance. By 1899 the electrical potential of his transmitter had increased to the point that more room was needed for the sake of safety. This and other considerations led him to temporarily shift his wireless experiments to a location just outside of Colorado Springs.

Historical Problems:

    Tesla described his wireless power transmission method by three characteristics: 1) the reduction or elimination of electromagnetic radiations, 2) that it operated through the earth, and 3) that the mechanism of transmission is an electric current - as contrasted with radiations. Modern analysts, on the other hand, model Tesla's transmission system on present day broadcast radio technology. This model assumes an antenna propagating electromagnetic waves into the air where these radiations either will not or will, depending on the presuppositions of the writer, bring about the effects claimed by the inventor.

    Anachronistic interpretation - applying the assumptions of today's electrical theories to Tesla's original turn of the century researches - is only half the problem of understanding the inventor's wireless method. The situation is further complicated by the similar sounding descriptions Tesla gave to his earlier and later transmission techniques.

    In his early work Tesla attempted electronic transmission by modifying the atmosphere. This is the case in his patent entitled Method of Intensifying and Utilizing Effects Transmitted Through Natural Media, #685,953, applied for in June 1899. In this patent he proposes a very powerful signal generator to ionize atmospheric gases and, by that, create a conductive path between the transmitter and receiver through which a current could be sent. Later, when Tesla disclosed what he described as through-the-earth (or water) transmission with essentially the same type of apparatus and operating at ELF frequencies, it has been assumed by modern authorities that Tesla was mistaken about his method of propagation and was really witnessing earth-ionosphere cavity resonance at Schuman frequencies [1,2].

    Tesla, though, was more than an engineer of conventional methods. He was an electrical researcher who investigated fundamental issues of the science. It will be shown that the three characteristics of Tesla's wireless transmission system describe an electrostatic wireless method that used the earth as a conductor and transmitted displacement currents. At moderate power levels the system could be used for communication. At greater levels, power could be sent by wireless.

Experiments:

    At this Colorado "Experimental Station" Tesla had some early success in wireless power transmission. One photograph shows that "a small incandescent lamp was lighted by means of a resonant circuit grounded on one end, all the energy being drawn through the earth [from a nearby transmitter]." In 1907 he even went as far as to make this statement: "... to make the little filament glow, the entire surface of the planet, two hundred million square miles, must be strongly electrified. This calls for peculiar electrical activities, hundreds of times greater than those involved in the lighting of an arc lamp through the human body [a far more spectacular demonstration]. What impresses him most, however, is the knowledge that the little lamp will spring into the same brilliancy anywhere on the globe, there being no appreciable diminution of the effect with the increase of distance from the transmitter."

    It is not at all clear that Tesla was referring to effects produced by his large Colorado transmitter. It is quite possible that he was writing about what he felt could be done with an even bigger transmitter such as the one that he was developing in New York. If the Wardenclyffe communications facility had been finished, the 187 foot tall mushroom-shaped tower would have permanently housed a set of large coils including an immense helical resonator that would have served as the main transmitting element. Directly below the wooden tower there was a 120 foot shaft where deep underground Tesla had installed a radial array of iron pipes that served as a connection between the oscillator and the earth.

   

    The Wardenclyffe plant was a major milestone in Tesla's researches into the application of alternating electrical currents to wireless communications and power transmission, an effort which drew a considerable amount of Tesla's attention during the period between 1891 and 1912. In the article "The Future of the Wireless Art" which appeared in Wireless Telegraphy & Telephony, 1908, Tesla made the following statement regarding the Wardenclyffe project on which he was then working: "As soon as completed, it will be possible for a business man in New York to dictate instructions, and have them instantly appear in type at his office in London or elsewhere. He will be able to call up, from his desk, and talk to any telephone subscriber on the globe, without any change whatever in the existing equipment. An inexpensive instrument, not bigger than a watch, will enable its bearer to hear anywhere, on sea or land, music or song, the speech of a political leader, the address of an eminent man of science, or the sermon of an eloquent clergyman, delivered in some other place, however distant. In the same manner any picture, character, drawing, or print can be transferred from one to another place. Millions of such instruments can be operated from but one plant of this kind. More important than this, however, will be the transmission of power, without wires, which will be shown on a scale large enough to carry conviction. These few indications will be sufficient to show that the wireless art offers greater possibilities than any invention or discovery heretofore made, and if the conditions are favorable, we can expect with certitude that in the next few years wonders will be wrought by its application."

   

After the Experiments:

    In the end, Tesla was never able to complete the Wardenclyffe plant, although he was able to conduct some performance tests. Nevertheless, if the above stated predictions were to be true, an interesting feature of Tesla's World System for global communications, had it gone into full operation, would have been its capacity to provide small but usable quantities of electrical power at the location of the receiving circuits. He predicted that further advances would have permitted the wireless transmission of industrial amounts of electrical energy with minimal losses to any point on the earth's surface. Had he been able to complete the prototype station on Long Island and use it to demonstrate the feasibility of wireless power transmission then a plan would have been implemented for the construction of a pilot plant for this larger system at Niagara Falls, site of the world's first commercial three phase AC power plant.

Future Objectives:

    The successful resonating of the Schumann Cavity and wirelesstransmission of power on a small scale resulting in proof of principle will require a second phase of engineering, the design of receiving stations. On completion of the second phase, the third and fourth phases of the project involving further tests and improvements and a large scale demonstration project will be pursued to prove commercial feasibility. Total cost from proof of principle to commercial prototype is expected to total $3 million.