In every field of life and practice, things change over the course of time. But like the proverbial “upcoming artist” some things offer so much in terms of potential but grow so slowly that hope seems to die out. One such trend is wireless electricity.  The area of wireless power transmission is very interesting. The technology is in its infancy but the overall benefits from its maturation could be significant to society as a whole.

You would be surprised to know that wireless electricity is not as new in application as it may sound to the ear.

In the late 19th century, Heinrich Hertz and Nicolai Tesla both theorized the possibility of wireless power transmission. In 1899, Tesla demonstrated it by powering fluorescent lamps 25 miles from the power source without using wires.  Despite the novelty of Tesla’s demonstration and his personal efforts to commercialize this innovation, he soon ran out of funding because it was a whole lot less expensive to lay copper than to build the equipment necessary to  transmit power through radio waves.

William C. Brown, an American electrical engineer who helped to invent the crossed-field amplifier in the 1950s, contributed much to the modern development of microwave power transmission which for many reasons dominates research and development of wireless transmission today.

In the early 1960s, Brown invented the rectenna which directly converts microwaves to DC current. He demonstrated its ability in 1964 by powering a helicopter from this solely through microwaves.

“In 1982, Brown (Raytheon) and James F. Trimer (NASA) announced the development of a thin-film plastic rectenna using printed-circuit technology that weighed only one-tenth as much as any previous rectenna”. This new, lighter weight rectenna led to the development of the Stationary High Altitude Relay Platform (SHARP). No commercial development past the prototype stage has been funded todate.

Many researchers are looking to use magnetrons instead because they are cheap and efficient. Magnetron frequency output however is not as precisely controllable as the klystron or travelling wave tube (TWT) that are used for microwave transmission, but power transmission is more lenient to frequency fluctuations than communication systems are. One of the more common proposals would be for an array of magnetrons to be used as the transmitter.

An alternative approach was pursued by an MIT (Massachusetts Institute of Technology) team that exploited some near field interaction between the source and device so that efficient power transfer was possible. The approach was evanescent wave coupling or resonant inductive coupling.

Despite all these, wireless power transmission has not been commercialized except for the sole exception of pacemakers and electric toothbrush rechargers and very recently smartphone rechargers.  However, the future indeed is bright for this trend.

This article make reference to:

  1. http://web.pdx.edu/~larosaa/Applied_Optics_464-564/Projects_Presented/Projects-2006/Andrew_Bomber_Report_Wireless_Power_Transmission_PH464.pdf
  2. https://en.wikipedia.org/wiki/Resonant_inductive_coupling
  3. http://www.cornellcollege.edu/physics-and-engineering/pdfs/phy-312/mandip-sibakoti.pdf