WiTricity

WiTricity, a portmanteau for wireless electricity, is a term coined initially by Dave Gerding in 2005 and used by a MIT research team led by prof. Marin Soljačić in 2007, to describe the ability to provide electricity to remote objects without wires. WiTricity is based on strong coupling between electromagnetic resonant objects to transfer energy wirelessly between them. The system consists of WiTricity transmitters and receivers that contain magnetic loop antennas critically tuned to the same frequency. As WiTricity operates in the electromagnetic near-field, the receiving devices must be within medium range (few meters) from the transmitter. The system uses a relatively low frequency (few MHz). In their first paper, the group also simulated GHz dielectric resonators.

Unlike the far field wireless power transfer systems based on electric field coupling, built by Nikola Tesla in the late 19th century, WiTricity employs near field coupling through magnetic fields, which interact much weaker with surrounding objects, including biological tissue. The WiTricity concept is fundamentally identical to the near field magnetically coupled Tesla coil resonators, albeit WiTricity uses considerably lower and safer power levels and thus may be able to meet FCC and EMC regulations. Near-field technologies draw power from the transmitter when a receiver is nearby, but with far-field techniques, the source is always transmitting power in all directions, even if there is no receiver. The researchers attribute lack of previous development of this technology from long-known physical laws to a lack of motivation; modern consumer have a high number of portable electronic devices which currently require batteries and plug-in chargers.

The MIT researchers successfully demonstrated the ability to power a 60 watt light bulb from a power source that was 2 meters (7 ft) away at roughly 40% efficiency. They used two copper coils, 60 centimeters (24 in) in diameter, designed to resonate together at 10 MHz. One was connected inductively to a power source, the other to a bulb. The setup powered the bulb on, even when the coils were not in line of sight. Aristeidis Karalis says that "the usual non-resonant magnetic induction would be almost 1 million times less efficient in this particular system".

The researchers plan to miniaturize the setup enough for commercial use in three to five years. The researchers suggest that the radiated power densities can be brought below the threshold for FCC safety regulations.

See also

• Wireless energy transfer
• Evanescent wave coupling

References

• Aristeidis Karalis (2007). "Efficient wireless non-radiative mid-range energy transfer". arXiv:physics/0611063v2. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help).
• Aristeidis Karalis (2007). "Efficient wireless non-radiative mid-range energy transfer". Annals of Physics. doi:10.1016/j.aop.2007.04.017. (Subscription required) {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
• Andre Kurs (2007). "Wireless power transfer via strongly coupled magnetic resonances". Science Express. doi:10.1126/science.1143254. (Subscription required) {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)

External links

• Jonathan Fildes (2007-06-07). "Wireless energy promise powers up". BBC News. {{cite news}}: Check date values in: |date= (help)
• Jonathan Fildes (2007-06-07). "Wireless energy promise powers up". BBC News. {{cite news}}: Check date values in: |date= (help)
• John McGullam (2007-06-21). "Wireless electricity power revealed". Wifi Electrics. {{cite news}}: Check date values in: |date= (help)
• "Breakthrough to a wireless (electricity) future (WiTricity)". The Press Association. 2007-06-07. {{cite news}}: Check date values in: |date= (help)
• Katherine Noyes (2007-06-08). "MIT Wizards Zap Electricity Through the Air". TechNewsWorld. {{cite news}}: Check date values in: |date= (help)
• Chris Peredun, Kristopher Kubichi (2007-06-11). "MIT Engineers Unveil Wireless Power System". DailyTech. {{cite news}}: Check date values in: |date= (help)