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  1. 1. TRISHA SINGHB070309EE*
  2. 2. *Wireless power transmission dates back to the19th century when Nikola Tesla used conduction-based systems to transfer wireless power.*A couple of techniques of wireless powertransmission are known now:*Direct induction*Resonant magnetic induction*Electromagnetic radiation*
  3. 3. **WiTricity stands for wireless electricity.*It is a trademark of WiTricity Corporation*It refers to their devices and processes whichemploy wireless energy transfer through resonantinductive coupling.*It is used to describe the ability to provideelectricity to remote objects without wires, usingoscillating magnetic fields
  4. 4. *The first experiment of WiTricity wasconducted in the year 2006 by a five-member team of researchers fromMassachusetts Institute of Technology.*It was led by Assistant Professor MarinSoljačić.*It was funded by Army Research Office,National Science Foundation and theDepartment of Energy.**
  5. 5. *Resonance is the tendency of a system to oscillatewith larger amplitude at some frequencies than atothers.* At the resonant frequencies, even small periodicdriving forces can produce large amplitudeoscillations, because the system stores vibrationalenergy.*Two objects having similar resonance tend toexchange energy without causing any effects on thesurrounding objects.*
  6. 6. *Just like in acoustic resonance,where there is a chance of aglass breaking if you strike theright tone.*A wine glass captures soundenergy that oscillates at itsnatural resonant frequency,converts it to mechanicalenergy that causes the glass todeform at that same frequencyand eventually causing it toshatter.*
  7. 7. *Two copper coils of diametertwo feet*The transmitter coil wasattached to a power source*The receiver coil was placedabout seven feet from thetransmitter* This receiver was attached toa light bulb and*The two coils were tuned tothe same frequency*Power was switched on at thetransmitter**
  8. 8. *The coils magnetically coupledand resonated at 10MHz.*Electric energy wastransmitted over a distance oftwo meters, through the airand around an obstacle.*With each cycle, morepressure and voltage built upin the coil till theaccumulation of voltageprovided enough pressure andenergy to flow to the lightbulb**
  9. 9. *Data collected throughmeasurements showed thatthere was transference of 40%of electricity throughWiTricity.*The bulb glowed despite thefact that wood, metal andother devices were placed inbetween the two coils**
  10. 10. *The blue lines represent themagnetic near field inducedby the power source.*The yellow lines represent theflow of energy from the sourceto the WiTricity capture coil.*The magnetic field (blue lines)can wrap around a conductiveobstacle between the powersource and the capturedevice.**
  11. 11. * WiTricity is based on strong coupling between electromagnetic resonantobjects to transfer energy wirelessly between them. This differs from othermethods like simple induction, microwaves, or air ionization.* The system uses two coils - one plugged into the mains (transmitter) and theother embedded or attached to the gadget(receiver). Each coil is carefullyengineered with the same resonant frequency.*
  12. 12. * When the main coil is connected to an electricity supply, the magnetic field itproduces is resonant with that of with the second coil, allowing "tails" of energy toflow between them.* As each "cycle" of energy arrives at the second coil, a voltage begins to build upthat can be used to charge the gadget.* Due to operating in the electromagnetic near field, the receiving devices must beno more than about a quarter wavelengths from the transmitter, which usuallycomes to around a few meters.*
  13. 13. *
  14. 14. **WiTricitys mode of wireless power transfer is highlyefficient over distances ranging from centimeters toseveral meters. In many applications, efficiency canexceed 90%.*Also, WiTricity sources only transfer energy when it isneeded.* When a WiTricity powered device no longer needs tocapture additional energy, the WiTricity power source willautomatically reduce its power consumption to a powersaving “idle” state.*
  15. 15. *Energy Transfer via Magnetic Near Field CanPenetrate and Wrap Around Obstacles*Flexible Geometry Allows WiTricity Devicesto be embedded into OEM Products*Scalable Design Enables Solutions frommilliwatts to Kilowatts*
  16. 16. **WiTricity’s technology is a non-radiative mode of energytransfer, relying instead on the magnetic near field.*Magnetic fields interact very weakly with biologicalorganisms—people and animals—and are scientificallyregarded to be safe.*The exposure levels are below the threshold for FCC safetyregulations, and the radiated-power levels comply with theFCC radio interference regulations*
  17. 17. *Wirelessly powering up an appliance will not add up appreciablyto the costs; though in the early days, the charging costs maybeup to 10-15% higher than in wired appliances*
  18. 18. *An electric toothbrush uses traditionalmagnetic induction to recharge its batteries.*The tooth brush needs to be placed in itscradle in order to be recharged, because thecoils must be within millimeters of each otherto couple and transfer power.**However, WiTricity’s specially designed magnetic resonatorsenable strong coupling and highly efficient energy exchangeover distances much larger than the size of the resonatorcoils, distances very large compared to traditional schemes.
  19. 19. *Radiative power transfer-*Broadcasted radiation*Directed radiation*Laser**WiTricity’s technology for power transfer is non-radiativeand relies on near-field magnetic coupling. It does notrequire a clear line of sight between the power sources andcapture devices and it is safe for use in typical home,hospital, office, or industrial environments.
  20. 20. *Back in the 19th century, Nikola Tesla usedconduction- based systems to transfer wirelesspower.*However, his grand scheme to beam electricityaround the world ran out of funding.*Also, interest in wireless power transmissionfaded away soon as the industrial worldwillingly adopted the wired approach.**WiTricity technology for power transfer isdifferent than the technologies proposedby Tesla, but his work is referenced andacknowledged in the scientific articlespublished by WiTricity’s founding technicalteam.Wardenclyffe tower
  21. 21. *WiTricity’s wireless power transfer technology can be appliedin a wide variety of applications and environments.*WiTricity technology can be used to provide:*Direct Wireless Power - when all the power a device needs isprovided wirelessly, and no batteries are required. This modeis for a device that is always used within range of its WiTricitypower source.*Automatic Wireless Charging - when a device withrechargeable batteries charges itself while still in use or atrest, without requiring a power cord or battery replacement.This mode is for a mobile device that may be used both in andout of range of its WiTricity power source.*
  22. 22. *Consumer electronics**Industrial
  23. 23. *Transportation**Miscellaneous
  24. 24. *
  25. 25. *With the advent of portable electronics that seem to needconstant charging, researchers are exploring ways tomake wireless electricity practical. In addition, plug-inelectric vehicles are another motivating factor, asplugging in a car or forgetting to plug one in, is a burdenthat consumers may not want to bear.*WiTricity Corp. is working towards miniaturizing andpackaging the technology so that it can be built directlyinto a wide variety of products and systems—with no needfor an external power capture device as shown in theprototype configuration.*
  26. 26. *André Kurs, AristeidisKaralis, Robert Moffatt, J. D.Joannopoulos, Peter Fisher, Marin Soljačić, ―WirelessPower Transfer via Strongly Coupled MagneticResonances‖, Science, Vol. 317, no. 5834, 6 July 2007, pp.83-86*AristeidisKaralis; J.D. Joannopoulos, Marin Soljačić,"Efficient wireless non-radiative mid-range energytransfer",Annals of Physics,April 2007, Vol. 323, pp. 34–48*WiTricity Corporation, http://www.witricity.com as onJanuary 9, 2011*