Wireless energy transfer

• US 8,097,983 B2
• Filed: 05/08/2009
• Issued: 01/17/2012
• Est. Priority Date: 07/12/2005
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Karalis, Aristeidis, Moffatt, Robert, Joannopoulos, John D., Fisher, Peter H., Soljacic, Marin, Kurs, Andre B
• Primary Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US12/437,641
• Publication Number:
  US 20090224856A1
• Time in Patent Office: 984 Days
• Field of Search: 307/104, 333/195
• US Class Current: 307/104
• CPC Class Codes: B60L 2210/20 AC to AC converters
• CPC Class Codes: B60L 53/126 Methods for pairing a vehicle and a charging station, e.g. establishing a one-to-one relation between a wireless power transmitter and a wireless power receiver
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/04 Resonant antennas
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

Disclosed is an apparatus for use in wireless energy transfer, which includes a first resonator structure configured to transfer energy non-radiatively with a second resonator structure over a distance greater than a characteristic size of the second resonator structure. The non-radiative energy transfer is mediated by a coupling of a resonant field evanescent tail of the first resonator structure and a resonant field evanescent tail of the second resonator structure.

Claims

1. A system, comprising:

a source resonator optionally coupled to an energy source;

a second resonator located a distance from the source resonator; and

a third resonator located a distance from the source resonator and the second resonator;

wherein the source resonator, the second resonator, and the third resonator are coupled to provide non-radiative wireless energy transfer among the resonators and wherein the second resonator is configured to receive energy from the source resonator and to transfer energy to the third resonator,

wherein each resonator is an electromagnetic resonator having an angular resonant frequency ω

, an intrinsic loss rate Γ

, and a Q-factor Q=ω

/(2Γ

), and wherein the Q-factor for at least one of the resonators is greater than 100.

2. The system of claim 1, wherein each electromagnetic resonator has a capacitance and an inductance defining the resonant frequency ω

.

3. The system of claim 2, wherein each electromagnetic resonator comprises an inductor and a capacitor.

4. The system of claim 1, wherein the Q-factor for at least one of the resonators is greater than 300.

5. The system of claim 1, wherein the Q-factor for the source resonator is greater than 100.

6. The system of claim 1, wherein the Q-factor for at least one other resonator is greater than 100.

7. The system of claim 1, further comprising the energy source providing energy to the source resonator, and wherein the source resonator has a characteristic size L_S, and the non-radiative wireless energy transfer from the source resonator to the third resonator through the second resonator extends over a distance D>

L₃.

8. The system of claim 1, further comprising the energy source providing energy to the source resonator, and wherein the third resonator has a characteristic size L₃, and the non-radiative wireless energy transfer from the source resonator to the third resonator through the second resonator extends over a distance D>

L₃.

9. The system of claim 8, wherein the non-radiative wireless energy transfer from the source resonator to the third resonator through the second resonator extends over a distance D>

2 L₃.

10. The system of claim 8, wherein the non-radiative wireless energy transfer from the source resonator to the third resonator through the second resonator extends over a distance D>

3 L₃.

11. The system of claim 8, wherein the non-radiative wireless energy transfer from the source resonator to the third resonator through the second resonator extends over a distance D>

5 L₃.

12. The system of claim 1, wherein at least one resonator is movable relative to the other resonators.

13. The system of claim 1, further comprising one or more additional electromagnetic resonators to facilitate the coupling between any of the source resonator, the second resonator, and the third resonator.

14. The system of claim 1, wherein the third resonator is directly coupled to a load in a device.

15. The system of claim 14, wherein the directly coupling between the third resonator and the load is an inductive coupling.

16. The system of claim 1, further comprising the energy source providing the energy to the source resonator, and wherein the energy source is directly coupled to the source resonator.

17. The system of claim 16, wherein the direct coupling between the energy source and the source resonator is an inductive coupling.

18. The system of claim 14, wherein the device comprises at least one of a robot, a mobile electronic device, a computer, a sensor, a vehicle, a medical device configured to be implanted in a patient, a television screen, a wireless keyboard, and a wireless mouse.

19. The system of claim 14, wherein the second resonator is directly coupled to another load in another portable electronic device.

20. The system of claim 1, further comprising the energy source providing energy to the source resonator, and wherein wireless energy transfer flows from the source resonator to each of the second and third resonators.

21. The system of claim 14, wherein the system provides the wireless energy to the load at a rate greater than 1 Watt.

22. The system of claim 21, wherein the system provides the wireless energy to the load at a rate greater than 30 Watt.

23. The system of claim 1, wherein the absolute difference between any two of the resonator frequencies is less than the largest of the intrinsic loss rates for the resonators.

24. The system of claim 1, further comprising the energy source providing electromagnetic energy to the source resonator at a source frequency f.

25. The system of claim 24, wherein the source frequency f is at least larger than 100 kHz and smaller than 500 MHz.

26. The system of claim 25, wherein the source frequency f is at least larger than 1 MHz and smaller than 50 MHz.

27. The system of claim 24, wherein the source frequency f is within one of the frequency bands specially assigned for industrial, scientific, and medical (ISM) equipment.

28. The system of claim 1, wherein at least one resonator comprises a self-resonant coil of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon.

29. The system of claim 1, wherein at least one resonator comprises a capacitively loaded loop or coil of at least one of a conducting wire, a conducting Litz wire, and a conducting ribbon.

30. The system of claim 1, wherein at least one of the resonators is tunable.

31. The system of claim 1, further comprising a feedback mechanism for improving the wireless energy transfer among the resonators.

32. The system of claim 31, wherein the feedback mechanism comprises an oscillator with a fixed frequency and is configured to adjust the resonant frequency of one or more of the resonators to be about equal to the fixed frequency to maintain resonance among the resonators.

33. The system of claim 31, further comprising the energy source providing energy to the source resonator, where the feedback mechanism is configured to monitor an efficiency of the wireless energy transfer from the source resonator to one or more of the remaining resonators, and adjust the resonant frequency of at least one of the resonators to increase the efficiency.

34. The system of claim 31, wherein the feedback mechanism provides information exchange among at least some of the resonators.

35. The system of claim 1, wherein the energy source is directly coupled to the first resonator and the third resonator is directly coupled to a load, and wherein the energy source is configured to be driven to increase the ratio of useful-to-lost power for the wireless energy transfer.

36. A system for use in wireless energy transfer, the system comprising:

a first electromagnetic resonator having an angular resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

/(2Γ

);

a second electromagnetic resonator having an angular resonant frequency ω

₁, an intrinsic loss rate Γ

₂, and a first Q-factor Q₂=ω

/(2Γ

); and

one or more additional electromagnetic resonators,

wherein the electromagnetic resonators are coupled to provide non-radiative wireless energy transfer among the resonators, and wherein at least one of Q₁ and Q₂ is greater than 100.

37. The system of claim 36, further comprising an energy source directly coupled to at least one of the resonators and a load directly coupled to another of the resonators.

38. The system of claim 37, further comprising a second load directly coupled to a further one of the resonators.

39. The system of claim 37, further comprising a second energy source directly coupled to a further one of the resonators.