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Wireless power presentation

  1. 1. Wireless PowerBy Jenna Rock and Loren Schwappach For Jing Guo – Electromagentics March 2010
  2. 2. Overview History Recent Developments Technical Details Demonstration Advantages and Disadvantages Variants and Evolution of Technology
  3. 3. History Nikola Tesla’s experiments (1900s)  Experiments conducted by Nikola Tesla over 100 years ago.  The Chicago World’s Fair Demonstration in 1893.  Required a clear line-of-site.  Second proposed system used the earth’s ionosphere.  Investors could not see a way to manage and profit from Tesla’s ideas. Wireless power via highly elliptical antennas (1970s)  June 5, 1975 NASA JPL Goldstone demonstration.  34kw of power at a distance of 1.5km; 82% efficiency.  Seen as impractical due to atmospheric absorption and free space loss. Wireless power in the Twentieth Century (2000s)  Today the most popular approach to wireless power uses inductive charging.  Considered a type of short distance wireless energy transfer.  Impractical for separation of more than a few inches.
  4. 4. Recent DevelopmentsMassachusetts Institute of Technology (MIT) Experiment Project Lead: Marin Soljačić Solution: wireless power transfer via strongly coupled magnetic resonances. Concept: “WiTricity” (Wireless Electricity) Overcomes several major drawbacks  Free space loss and atmospheric absorption.  Requirement for unobstructed line-of-sight (Lasers & HDAs).  Close-range and very low-power energy transfer limitations. “WiTricity” concept 106 times better than magnetic induction.
  5. 5. Technical Details Magnetic Induction  Loop or coil of conductive material like copper, carrying an AC current, to generate an oscillating magnetic field.  When second conducting loop (receiver) is brought close enough to the first, it captures a portion of the oscillating magnetic field, inducing an electric current in the second coil.  The current it drives around the circuit opposes the change in magnetic flux (Lenz’s Law).  When the current reverses direction, the magnetic field also reverses its direction. Faradays law of Coupling electromagnetic induction:  Conductors are referred to as inductively or E= -dφB/dt magnetically coupled when they are configured such E = electromotive force. that change in current flow through one induces a φB = magnetic flux. voltage across the ends of the other through electromagnetic induction.  A simple example is a locomotive pulling a train car.
  6. 6. Technical Details (Continued) Resonance:  The tendency of a system to oscillate at larger amplitude at some frequencies than at others.  These are known as the systems resonant frequencies.  At these frequencies, even small periodic driving forces can produce large amplitude oscillations.  Opera singer example, swing example. Resonant Magnetic Coupling:  Magnetic coupling occurs when two objects exchange energy through their oscillating magnetic fields.  All resonators have a Q (Quality) factor characterizes a resonators bandwidth relative to its center frequency, a tuning fork has a resonance of approx 1000.
  7. 7. Technical Details (Continued)The MIT Experiment Used two self-resonant coils, single copper loops (r =25 cm). One coil (the source coil) is coupled inductively to an oscillating circuit; the other (the device coil) is coupled inductively to a resistive load. The transmitting coil output a 9.9MHz resonating magnetic field. The resulting resonant frequency is: 1 f0  2 LC Both coils were separated by a distance of 2m with a 60W light connected to the receiving coil.
  8. 8. Demonstration
  9. 9. Advantages and Disadvantages Pros  No negative effect on humans.  “WiTricity” is using higher frequencies than pacemakers use, for example.  Efficient power transfer is only received by like resonant devices.  “WiTricity” magnetic field is << than earths.  No negative effects on the environment.  No more batteries ending up in landfills.  “WiTricity” is several thousand times more efficient than batteries and a million times more efficient than induction. Cons  Smallpower transmission waste due to coils (thermal energy).
  10. 10. Variants and Evolution of theTechnology Products and Applications  Consumer: phones, laptops, flat screen TV’s, digital pictures, home theater systems, speakers, and desktop PC’s and peripherals for use in home and “WiTricity” enabled hot spots.  Industrial: power interconnections across rotating and moving “joints” (think robotics, packing machinery, assembly machinery, machine tools), power interconnections in harsh environments (drilling, mining, underwater), robotics, and automatic guided vehicles.  Transportation: Automatic wireless powering for personal and commercial hybrid and future all electric vehicles and high tech military systems (mobile robotics, aircrafts, etc). Evolution of “WiTricity” technology  Smaller scale WiTricity fixed receivers, capable of enabling the WiTricity transmitters within an area.  WiTricity on a larger scale (street “WiTricity” transmitters), recreational use.
  11. 11. Conclusion  Wireless power transfer is quickly becoming a viable reality. “WiTricity” products expected in 2011  “WiTricity” offers an extremely efficient alternative to previous attempts at providing wireless power.  Future improvements in wireless power technology offer world changing implications.
  12. 12. ReferencesF. Hadley,. (2007). “Goodbye wires”. (PDF) “MIT_WiTricity_Press_Release.pdf”J. Dix. (2010). “Wireless power” Retrieved March 17, 2010, from http://www.networkworld.com/news/2010/011210-witricity.html?page=1A. Kurs., A. Karalis., R. Moffatt., P. Fisher., & M. Soljacic. (2007). “Wireless power transfer via strongly coupled magnetic resonances”. Science Express. (n.d.).A. Kurs. (2007). “Wireless power transfer via strongly coupled magnetic resonances. Science. 317(7), 83,A. Karalis., J. Joannopoulos., & Marin Soljacic. (2007). Efficient wireless non- radiative mid-range energy transfer. Annals of Physics. 323(2008), 34-48.
  13. 13. Questions?