WiTricity, a portmanteau for "wireless electricity", is a trademark of WiTricity corporation referring to their devices and processes which use a form of wireless energy transfer, the ability to provide electrical energy to remote objects without wires using oscillating magnetic fields. The term WiTricity was used for a project led by Prof. Marin Soljačić in 2007.
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.
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". 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.
It has been more than 100 years since this technology was initially discovered. Researchers attribute the delay to develop the 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.
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. The coils were designed to resonate together at 9.9 MHz 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.
The emerging technology was demonstrated by Eric Giler, CEO of the US firm WiTricity, at the TED Global Conference held at Oxford in July 2009. In this demonstration, Giler shows a WiTricity power unit powering a television as well as three different cell phones.
- List of emerging technologies
- Nikola Tesla
- Electrosmog energy harvesting
- Resonant energy transfer
- Coupled inductors
- Evanescent wave coupling
- WREL technology
- ↑ 
- ↑ "Wireless electricity could power consumer, industrial electronics". MIT News. 2006-11-14. http://web.mit.edu/newsoffice/2006/wireless.html.
- ↑ 3.0 3.1 3.2 "Goodbye wires…". MIT News. 2007-06-07. http://web.mit.edu/newsoffice/2007/wireless-0607.html.
- ↑ "Wireless Power Demonstrated". http://thefutureofthings.com/pod/250/wireless-power-demonstrated.html. Retrieved 2008-12-09.
- ↑ Fildes, Jonathan (2009-07-23). "Wireless power system shown off". BBC News Online. http://news.bbc.co.uk/2/hi/technology/8165928.stm. Retrieved 2009-09-13.
- ↑ "Eric Giler demos wireless electricity". TED. 2009-07. http://www.ted.com/talks/eric_giler_demos_wireless_electricity.html. Retrieved 2009-09-13.
- ↑ Electrical recharging using electrosmog]
- Aristeidis Karalis; J.D. Joannopoulos, Marin Soljačić (January 2008). [Expression error: Missing operand for > "Efficient wireless non-radiative mid-range energy transfer"]. Annals of Physics 323: 34–48. doi:10.1016/j.aop.2007.04.017. "Published online: April 2007".
- Andre Kurs; Aristeidis Karalis, Robert Moffatt, J.D. Joannopoulos, Peter Fisher, Marin Soljačić (July 2007). [Expression error: Missing operand for > "Wireless power transfer via strongly coupled magnetic resonances"]. Science 317: 83–86. doi:10.1126/science.1143254. PMID 17556549. "Published online: June 2007".
- "Marin Soljačić (researcher team leader) home page on MIT". http://www.mit.edu/%7Esoljacic/wireless_power.html.
- Jonathan Fildes (2007-06-07). "Wireless energy promise powers up". BBC News. http://news.bbc.co.uk/2/hi/technology/6725955.stm.
- JR Minkel (2007-06-07). "Wireless Energy Lights Bulb from Seven Feet Away". Scientific American. http://www.sciam.com/article.cfm?articleid=07511C52-E7F2-99DF-3FA6ED2D7DC9AA20&chanId=sa025.
- "Breakthrough to a wireless (electricity) future (WiTricity)". The Press Association. 2007-06-07. http://www.breitbart.com/article.php?id=paWirelessThur19Wirelesspower&show_article=1&catnum=0.
- Katherine Noyes (2007-06-08). "MIT Wizards Zap Electricity Through the Air". TechNewsWorld. http://www.technewsworld.com/story/57757.html.
- Chris Peredun, Kristopher Kubichi (2007-06-11). "MIT Engineers Unveil Wireless Power System". DailyTech. http://www.dailytech.com/MIT+Engineers+Unveil+Wireless+Power+System/article7632.htm.
- "Supporting Online Material for Wireless Power Transfer via Strongly Coupled Magnetic Resonances". Science Magazine. http://www.sciencemag.org/cgi/data/1143254/DC1/1.
- Gary Peterson (2008-08-06). "Anticipating Witricity". 21st Century Books. http://www.tfcbooks.com/articles/witricity.htm.
- William C. Brown biography on the IEEE MTT-S website
- Anuradha Menon (2008-11-14). "Intel’s Wireless Power Technology Demonstrated". The Future of Things e-magazine. http://thefutureofthings.com/news/5763/intel-s-wireless-power-technology-demonstrated.html.
- WiTricity Explained
- Cutting the Cord article from physics.org
- Ovidiu (2009-12-03). "WiTricity To Be Used In First Wirelessly Powered Devices by Next Christmas". The green optimistic. http://www.greenoptimistic.com/2009/12/03/witricity-commercial-launch/.