WiTricity

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WiTricity
Founder(s) Marin Soljačić
Headquarters Watertown, USA
Key people Eric Giler, CEO
Website www.witricity.com

WiTricity is an American engineering company that manufactures devices for wireless energy transfer using resonant energy transfer (oscillating magnetic fields).

Contents

History[edit]

The term WiTricity was used for a project that took place at MIT, led by Marin Soljačić in 2007.[1][2] The MIT researchers successfully demonstrated the ability to power a 60 watt light bulb wirelessly, using two 5-turn copper coils of 60 cm (24 in) diameter, that were 2 m (7 ft) away, at roughly 45% efficiency.[3] The coils were designed to resonate together at 9.9 MHz (≈ wavelength 30 m) and were oriented along the same axis. One was connected inductively to a power source, and the other one to a bulb. The setup powered the bulb on, even when the direct line of sight was blocked using a wooden panel. Researchers were able to power a 60 watt light bulb at roughly 90% efficiency at a distance of 3 feet[citation needed]. The research project was spun off into a private company, also called WiTricity.

The emerging technology was demonstrated by CEO Eric Giler at the TED Global Conference held at Oxford in July 2009.[4][5] In this demonstration, Giler shows a WiTricity power unit powering a television as well as three different cell phones, the initial problem which inspired Soljacic to get involved with the project.

In April 27, 2011, car maker Toyota made an investment in WiTricity.[6][7]

In September 2012, the company announced it would make a $1000 demonstration kit available to interested parties, to promote development of commercial applications.[8]

Technology[edit]

WiTricity is based on strong coupling between electromagnetic resonant objects to transfer energy wirelessly between them. This differs from other methods like simple induction, microwaves, or air ionization. The system consists of transmitters and receivers that contain magnetic loop antennas critically tuned to the same frequency. Due to operating in the electromagnetic near field, the receiving devices must be no more than about a quarter wavelength from the transmitter (which is a few meters at the frequency used by the example system). In their first paper, the group also simulated GHz dielectric resonators. The WiTricity devices are coupled almost entirely with magnetic fields (the electric fields are largely confined within capacitors inside the devices), which is argued to make them safer than resonant energy transfer using electric fields (most famously in Tesla coils, whose high electric fields allow them to be used as lightning generators), since most materials couple weakly to magnetic fields (Kurs, 2007). The WiTricity devices are also claimed to be unusual in that they support efficient energy transfer for "mid-range" distances several times larger than the diameter of the resonant objects (Karalis, 2007).

Unlike the far field wireless power transmission systems based on traveling electro-magnetic waves, WiTricity employs near field resonant inductive coupling through magnetic fields similar to those found in transformers except that the primary coil and secondary winding are physically separated, and tuned to resonate to increase their magnetic coupling. These tuned magnetic fields generated by the primary coil can be arranged to interact vigorously with matched secondary windings in distant equipment but far more weakly with any surrounding objects or materials such as radio signals or biological tissue.

In particular, WiTricity is based on using 'strongly-coupled' resonances to achieve a high power-transmission efficiency. Aristeidis Karalis, referring to the team's experimental demonstration, says that "the usual non-resonant magnetic induction would be almost 1 million times less efficient in this particular system".[2] The researchers suggest that the exposure levels will be below the threshold for FCC safety regulations, and the radiated-power levels will also comply with the FCC radio interference regulations.

Researchers attribute the delay in developing wireless-power technology to limitations of well-known physical laws and a simple lack of need. Only recently have modern consumers obtained a high number of portable electronic devices which currently require batteries and plug-in chargers.[2]

Radiation levels[edit]

See also: Electromagnetic radiation and health

The company's FAQ [1] claims that it uses a "non-radiative mode of energy transfer, relying instead on the magnetic near field. Magnetic fields interact very weakly with biological organisms — people and animals — and are scientifically regarded to be safe." No actual studies or reports are claimed of the specific technology, power levels and use in home environments, although it does claim that "WiTricity products are being designed to comply with applicable safety standards and regulations."

See also[edit]

References[edit]

  1. ^ "Wireless electricity could power consumer, industrial electronics". MIT News. 2006-11-14. 
  2. ^ a b c "Goodbye wires…". MIT News. 2007-06-07. 
  3. ^ "Wireless Power Demonstrated". Retrieved 2008-12-09. 
  4. ^ Fildes, Jonathan (2009-07-23). "Wireless power system shown off". BBC News Online. Retrieved 2009-09-13. 
  5. ^ "Eric Giler demos wireless electricity". TED. 2009-07. Retrieved 2009-09-13. 
  6. ^ Gordon-Bloomfield, Nikki (Apr 28, 2011). "Toyota Joins Wireless Electric Car Charging Revolution". Green Car Reports. Retrieved 24 April 2012. 
  7. ^ "TMC and WiTricity Form Wireless Battery-charging Alliance". Toyota Motor Corporation. April 27, 2011. Retrieved 24 April 2012. 
  8. ^ Scott Kirsner (2012-09-17). "Flying electricity and neighborhood news". Boston Globe. 
  9. ^ Electrical recharging using electrosmog

Reference articles[edit]

External links[edit]

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