Editing Wireless power transfer (section)

== Uses ==

Inductive power transfer between nearby wire coils was the earliest wireless power technology to be developed, existing since the [[transformer]] was developed in the 1800s.  [[Induction heating]] has been used since the early 1900s and is used for [[induction cooking]].<ref>{{Cite book |title=Handbook of Induction Heating |edition=Second |isbn=978-1351643764 |last1=Rudnev |first1=Valery |last2=Loveless |first2=Don |last3=Cook |first3=Raymond L |date=2017-07-14 |publisher=CRC Press}}</ref>

With the advent of [[cordless]] devices, induction charging stands have been developed for appliances used in wet environments, like [[electric toothbrush]]es and [[electric razor]]s, to eliminate the hazard of electric shock.  One of the earliest proposed applications of inductive transfer was to power electric locomotives.  In 1892 Maurice Hutin and Maurice Leblanc patented a wireless method of powering railroad trains using resonant coils inductively coupled to a track wire at 3&nbsp;kHz.<ref name="Patent527857A">{{cite patent |country=United States |number=527857A |status= |title=Transformer system for electric railways |pubdate= |gdate=23 October 1894 |fdate=16 November 1892 |invent1=Maurice Hutin |invent2=Maurice Leblanc |url=https://www.google.com/patents/US527857}}</ref>

In the early 1960s resonant inductive wireless energy transfer was used successfully in implantable medical devices<ref>{{cite journal |last1=Schuder |first1=J. C. |year=2002 |title=Powering an artificial heart: Birth of the inductively coupled-radio frequency system in 1960 |journal=Artificial Organs |volume=26 |issue=11 |pages=909–915 |doi=10.1046/j.1525-1594.2002.07130.x |pmid=12406141}}</ref> including such devices as pacemakers and artificial hearts.  While the early systems used a resonant receiver coil, later systems<ref>{{cite book |last1=SCHWAN |first1=M. A. |first2=P.R. |last2=Troyk |title=Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society |chapter=High efficiency driver for transcutaneously coupled coils |date=November 1989 |pages=1403–1404 |doi=10.1109/IEMBS.1989.96262 |s2cid=61695765}}</ref> implemented resonant transmitter coils as well. These medical devices are designed for high efficiency using low power electronics while efficiently accommodating some misalignment and dynamic twisting of the coils. The separation between the coils in implantable applications is commonly less than 20&nbsp;cm. Today resonant inductive energy transfer is regularly used for providing electric power in many commercially available medical implantable devices.<ref>{{cite web |url=http://www.cochlearamericas.com/Products/11.asp |title=What is a cochlear implant? |publisher=Cochlearamericas.com |date=2009-01-30 |access-date=2009-06-04 |url-status=dead |archive-url=https://web.archive.org/web/20081224181329/http://www.cochlearamericas.com/Products/11.asp |archive-date=2008-12-24}}</ref>

The first passive [[RFID]] (Radio Frequency Identification) technologies were invented by Mario Cardullo<ref name="Patent">{{cite patent |country=United States |number=3713148A |title=Transponder apparatus and system |gdate=23 January 1973 |fdate=21 May 1970 |invent1=Mario W. Cardullo |invent2=William L. Parks |url=http://www.google.com/patents/US3713148}}</ref> (1973) and Koelle et al.<ref name="Koelle">{{cite journal |last1=Koelle |first1=A. R. |last2=Depp |first2=S. W. |last3=Freyman |first3=R. W. |title=Short-range radio-telemetry for electronic identification, using modulated RF backscatter |journal=Proceedings of the IEEE |volume=63 |issue=8 |pages=1260–1261 |year=1975 |doi=10.1109/proc.1975.9928}}</ref> (1975) and by the 1990s were being used in [[proximity card]]s and contactless [[smartcard]]s.

The proliferation of portable wireless communication devices such as [[mobile phone]]s, [[tablet computer|tablet]], and [[laptop computer]]s in recent decades is currently driving the development of mid-range wireless powering and charging technology to eliminate the need for these devices to be tethered to wall plugs during charging.<ref name="Sayer">{{cite journal |last1=Sayer |first1=Peter |title=Wireless Power Consortium to Unleash Electronic Gadgets |journal=PC World |date=19 December 2008 |url=http://www.pcworld.com/article/155766/article.html |access-date=8 December 2014}}</ref> The [[Wireless Power Consortium]] was established in 2008 to develop interoperable standards across manufacturers.<ref name="Sayer" /> Its [[Qi (inductive power standard)|Qi]] inductive power standard published in August 2009 enables high efficiency charging and powering of portable devices of up to 5 watts over distances of 4&nbsp;cm (1.6 inches).<ref name="Qi">{{Cite news |title=Global Qi Standard Powers Up Wireless Charging |agency=PR Newswire |publisher=UBM plc |date=2 September 2009 |url=http://www.prnewswire.com/news-releases/global-qi-standard-powers-up-wireless-charging-102043348.html |access-date=8 December 2014}}</ref> The wireless device is placed on a flat charger plate (which can be embedded in table tops at cafes, for example) and power is transferred from a flat coil in the charger to a similar one in the device. In 2007, a team led by Marin Soljačić at MIT used a dual resonance transmitter with a 25&nbsp;cm diameter secondary tuned to 10&nbsp;MHz to transfer 60 W of power to a similar dual resonance receiver over a distance of {{convert|2|meters|feet}} (eight times the transmitter coil diameter) at around 40% efficiency.<ref name="LeeZhongHui" /><ref name="Kurs" />

In 2008 the team of Greg Leyh and Mike Kennan of Nevada Lightning Lab used a grounded dual resonance transmitter with a 57&nbsp;cm diameter secondary tuned to 60&nbsp;kHz and a similar grounded dual resonance receiver to transfer power through coupled electric fields with an earth current return circuit over a distance of {{convert|12|meters|feet}}.<ref name="Leyh-Kennan_2008">{{cite conference |first1=G. E. |last1=Leyh |first2=M. D. |last2=Kennan |title=2008 40th North American Power Symposium |chapter=Efficient wireless transmission of power using resonators with coupled electric fields |conference=NAPS 2008 40th North American Power Symposium, Calgary, 28–30 September 2008 |pages=1–4 |publisher=IEEE |date=28 September 2008 |chapter-url=http://www.lod.org/uploads/8/2/1/1/82111982/naps2008final.pdf |doi=10.1109/NAPS.2008.5307364 |isbn=978-1-4244-4283-6 |access-date=20 November 2014}}</ref> In 2011, Dr. Christopher A. Tucker and Professor [[Kevin Warwick]] of the [[University of Reading]], recreated Tesla's 1900 patent [[List of Nikola Tesla patents|0,645,576]] in miniature and demonstrated power transmission over {{convert|4|meters|feet}} with a coil diameter of {{convert|10|cm|in}} at a resonant frequency of 27.50&nbsp;MHz, with an effective efficiency of 60%.<ref name="Tucker">{{cite journal |last1=Tucker |first1=Christopher A. |last2=Warwick |first2=Kevin |last3=Holderbaum |first3=William |title=A contribution to the wireless transmission of power |journal=International Journal of Electrical Power & Energy Systems |volume=47 |pages=235–242 |year=2013 |url=https://www.academia.edu/3800273 |doi=10.1016/j.ijepes.2012.10.066 |bibcode=2013IJEPE..47..235T}}</ref>

A major motivation for microwave research in the 1970s and 1980s was to develop a satellite for [[space-based solar power]].<ref name="Shinohara" /><ref name="Brown1984"/> Conceived in 1968 by [[Peter Glaser]], this would harvest energy from sunlight using [[solar cell]]s and beam it down to Earth as [[microwave]]s to huge rectennas, which would convert it to electrical energy on the [[electric power grid]].<ref name="Glaser">{{cite journal |last=Glaser |first=Peter E. |title=Power from the Sun: Its future |journal=Science |volume=162 |issue=3856 |pages=857–861 |date=22 November 1968 |url=http://www.science-sainte-rose.net/GrandBassin/documents/downloads/GlaserSPS68.pdf |doi=10.1126/science.162.3856.857 |pmid=17769070 |access-date=4 November 2014 |bibcode=1968Sci...162..857G}}</ref> In landmark 1975 experiments as technical director of a JPL/Raytheon program, Brown demonstrated long-range transmission by beaming 475 W of microwave power to a rectenna a mile away, with a microwave to DC conversion efficiency of 54%.<ref name="Brown2">{{cite web |last1=Friend |first1=Michael |last2=Parise |first2=Ronald J. |title=Cutting the Cord: ISTF 07-1726 |url=http://mainland.cctt.org/istf2008/Brown.asp |publisher=Mainland High School, Daytona Beach, Florida |access-date=7 October 2016}}</ref> At NASA's Jet Propulsion Laboratory, he and Robert Dickinson transmitted 30&nbsp;kW DC output power across 1.5&nbsp;km with 2.38&nbsp;GHz microwaves from a 26 m dish to a 7.3 x 3.5 m rectenna array. The incident-RF to DC conversion efficiency of the rectenna was 80%.<ref name="Dickinson">{{cite book |doi=10.1109/mwsym.1976.1123672 |title=MTT-S International Microwave Symposium Digest |year=1976 |last1=Dickinson |first1=R.M. |chapter=Performance of a High-Power, 2.388-GHZ Receiving Array in Wireless Power Transmission over 1.54&nbsp;km |volume=76 |pages=139–141}}</ref> In 1983 Japan launched [[Microwave Ionosphere Nonlinear Interaction Experiment]] (MINIX), a rocket experiment to test transmission of high power microwaves through the ionosphere.{{citation needed|date=April 2021}}

In recent years a focus of research has been the development of wireless-powered drone aircraft, which began in 1959 with the Dept. of Defense's RAMP (Raytheon Airborne Microwave Platform) project<ref name="Brown1984"/> which sponsored Brown's research.  In 1987 Canada's Communications Research Center developed a small prototype airplane called [[Stationary High Altitude Relay Platform]] (SHARP) to relay telecommunication data between points on earth similar to a [[communications satellite]].  Powered by a rectenna, it could fly at 13 miles (21&nbsp;km) altitude and stay aloft for months. In 1992 a team at Kyoto University built a more advanced craft called MILAX (MIcrowave Lifted Airplane eXperiment).

In 2003 NASA flew the first laser powered aircraft.  The small model plane's motor was powered by electricity generated by [[photocell]]s from a beam of infrared light from a ground-based laser, while a control system kept the laser pointed at the plane.