Wireless non-radiative energy transfer

• US 8,084,889 B2
• Filed: 03/31/2009
• Issued: 12/27/2011
• Est. Priority Date: 07/12/2005
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Joannopoulos, John D., Karalis, Aristeidis, Soljacic, Marin
• Primary Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US12/415,616
• Publication Number:
  US 20090267709A1
• Time in Patent Office: 1,001 Days
• Field of Search: 307/104, 333/195
• US Class Current: 307/104
• 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: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H01Q 9/04 Resonant antennas
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02M 1/0064 Magnetic structures combining different functions, e.g. storage, filtering or transformation
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H04B 5/0037 for power transfer
• 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 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

The electromagnetic energy transfer device includes a first resonator structure receiving energy from an external power supply. The first resonator structure has a first Q-factor. A second resonator structure is positioned distal from the first resonator structure, and supplies useful working power to an external load. The second resonator structure has a second Q-factor. The distance between the two resonators can be larger than the characteristic size of each resonator. Non-radiative energy transfer between the first resonator structure and the second resonator structure is mediated through coupling of their resonant-field evanescent tails.

Claims

1. A system for wirelessly providing power to a load, the system comprising:

a first electromagnetic resonator configured to be coupled to a power supply, the first resonator having a characteristic size L₁, a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁);

a second electromagnetic resonator configured to be coupled to the load, the second resonator having a characteristic size L₂, a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂),

wherein the first and second resonators are configured to be wirelessly coupled to provide resonant non-radiative wireless power to the second resonator from the first resonator with a wireless energy transfer rate κ

, and

wherein the resonators satisfy κ

/√

{square root over (Γ

₁Γ

₂)}>

1 for at least some distances D between the first and second resonators satisfying D/L₂>

1.

2. The system of claim 1, wherein the distances D satisfy D/L₂>

2.

3. The system of claim 1, wherein the distances D satisfy D/L₂>

3.

4. The system of claim 1, wherein the distances D satisfy D/L₂>

5.

5. The system of claim 1, wherein the resonators further satisfy κ

/√

{square root over (Γ

₁Γ

₂)}>

1 for the distances D/L₂>

1 and different relative orientations of the first and second resonators.

6. The system of claim 1, wherein Q₁>

100.

7. The system of claim 1, wherein Q₂>

100.

8. The system of claim 1, wherein (√

{square root over (Q₁Q₂)})>

100.

9. The system of claim 1, wherein the first and second resonators are movable relative to one another.

10. The system of claim 1, further comprising the power supply coupled to the first resonator and the load coupled to the second resonator.

11. The system of claim 1, wherein the first resonator provides at least 10 W of wireless power to the second resonator.

12. The system of claim 1, wherein the efficiency of the wireless energy transfer from the first resonator to the second resonator is at least 20%.

13. The system of claim 12, wherein the distances D include 10 cm.

14. The system of claim 1, wherein the distances D include 5 cm.

15. The system of claim 1, wherein the distances D include 30 cm.

16. The system of claim 1, wherein the resonant frequencies f₁=ω

₁/2π and

f₂=ω

₂/2π

are each at least 5 MHz.

17. The system of claim 1, wherein said first resonator comprises a capacitive element and an inductive element.

18. The system of claim 1, wherein said second resonator comprises a capacitive element and an inductive element.

19. The system of claim 1, further comprising a feedback mechanism coupled to at least one of the resonators to correct for frequency detuning.

20. The system of claim 11, wherein the power supply and load are driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.

21. The system of claim 11, wherein the second resonator and the load are part of a portable electronic device.

22. The system of claim 21, wherein the portable electronic device is a cell phone, a computer, a robot, or a vehicle.

23. The system of claim 1, wherein the characteristic size of at least one of the resonators is at least 1 cm.

24. The system of claim 1, wherein the characteristic size of at least one of the resonators is at least 30 cm.

25. The system of claim 1, wherein the characteristic sizes of the first and second resonators are different from one another.

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

27. The system of claim 1, wherein the resonators satisfy κ

/√

{square root over (Γ

₁Γ

₂)}>

2 for the distances D.

28. The system of claim 1, wherein the resonators satisfy κ

/√

{square root over (Γ

₁Γ

₂)}>

5 for the distances D.

29. The system of claim 1, further comprising an additional electromagnetic resonator configured to receive resonant non-radiative wireless power from the first resonator.

30. A system for wirelessly providing power to a portable electronic device, the system comprising:

a first electromagnetic resonator coupled to a power supply, the first resonator having a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁);

a second electromagnetic resonator coupled to a load in the portable electronic device, the second resonator having a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂),

wherein the first and second resonators are wirelessly coupled to provide resonant non-radiative wireless power to the second resonator from the first resonator with a wireless energy transfer rate κ and

an efficiency of at least 20% for distances D of at least 10 cm between the first and second resonators.

31. The system of claim 30, wherein the portable electronic device is a cell phone, a computer, a robot, or a vehicle.

32. The system of claim 30, further comprising a feedback mechanism coupled to at least one of the resonators to correct for frequency detuning.

33. The system of claim 30, wherein the resonant frequencies f₁=ω

₁/2π and

f₂=ω

₂/2π

are each at least 5 MHz.

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

35. The system of claim 30, wherein at least one of Q₁ and Q₂ is greater than 100.

36. The system of claim 30, wherein the power supply and load are driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.

37. The system of claim 30, wherein each of the electromagnetic resonators comprise a capacitive element and an inductive element.

38. A portable electronic device for use with a first electromagnetic resonator coupled to a power supply, the first resonator having a characteristic size L₁, a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁), the portable electronic device comprising;

a load; and

a second electromagnetic resonator configured to be coupled to the load and movable relative to the first resonator, the second resonator having a characteristic size L₂, a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂),

wherein the second resonator is configured to be wirelessly coupled to the first resonator to provide resonant non-radiative wireless power to the second resonator from the first resonator with a wireless energy transfer rate κ

, and

wherein the resonators satisfy κ

/√

{square root over (Γ

₁Γ

₂)}>

1 for at least some distances D between the first and second resonators satisfying D/L₂>

1.

39. The device of claim 38, wherein Q₂>

100.

40. The device of claim 38, wherein (√

{square root over (Q₁Q₂)})>

100.

41. The device of claim 38, wherein the second resonator is tunable.

42. The device of claim 38, wherein the wireless power is at least 10 W.

43. The device of claim 38, wherein the device is a cell phone, a computer, a robot, or a vehicle.

44. The device of claim 38, wherein the resonant frequency f₂=ω

₂/2π

is at least 5 MHz.

45. The device of claim 38, wherein the efficiency of the wireless power transfer is at least 20% for distances D of at least 10 cm between the first and second resonators.

46. The device of claim 38, wherein during operation the load is driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.

47. A power source for wirelessly providing power to a portable electronic device, the power source comprising:

a power supply; and

a first electromagnetic resonator coupled to a power supply, the first resonator having a characteristic size L₁, a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁), the portable electronic device,

wherein the first resonator is configured to be wirelessly coupled to a second electromagnetic resonator in the portable electronic device to provide non-radiative wireless power to the second resonator from the first resonator with a wireless energy transfer rate κ

,

wherein the second electromagnetic resonator is coupled to a load in the portable electronic device and movable relative to the first resonator, the second resonator having a characteristic size L₂, a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂),

wherein the resonators satisfy κ

/√

{square root over (Γ

₁Γ

₂)}>

1 for at least some distances D between the first and second resonators satisfying D/L₂>

1.

48. The power source of claim 47, wherein Q₁>

100.

49. The power source of claim 47, wherein (√

{square root over (Q₁Q₂)})>

100.

50. The power source of claim 47, wherein the first resonator is tunable.

51. The power source of claim 47, wherein the wireless power is at least 10 W.

52. The power source of claim 47, wherein the device is a cell phone, a computer, a robot, or a vehicle.

53. The power source of claim 47, wherein the resonant frequency f₁=ω

₁/2π

is at least 5 MHz.

54. The power source of claim 47, wherein the efficiency of the wireless power transfer is at least 20% for distances D of at least 10 cm between the first and second resonators.

55. The power source of claim 47, wherein during operation the power supply is driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.

56. A portable electronic device for use with a first electromagnetic resonator coupled to a power supply, the first resonator having a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁), the portable electronic device comprising;

a load; and

a second electromagnetic resonator configured to be coupled to the load and movable relative to the first resonator, the second resonator having a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂),

wherein the second resonator is configured to be wirelessly coupled to the first resonator to provide resonant non-radiative wireless power to the second resonator from the first resonator with a wireless energy transfer rate κ

, and

wherein the efficiency of the wireless power transfer is at least 20% for distances D of at least 10 cm between the first and second resonators.

57. The device of claim 56, wherein Q₂>

100.

58. The device of claim 56, wherein (√

{square root over (Q₁Q₂)})>

100.

59. The device of claim 56, wherein the second resonator is tunable.

60. The device of claim 56, wherein the device is a cell phone, a computer, a robot, or a vehicle.

61. The device of claim 56, wherein the resonant frequency f₂=ω

₂/2π

is at least 5 MHz.

62. The device of claim 56, wherein during operation the load is driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.

63. A power source for wirelessly providing power to a portable electronic device, the power source comprising:

a power supply; and

a first electromagnetic resonator coupled to a power supply, the first resonator having a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁), the portable electronic device,

wherein the first resonator is configured to be wirelessly coupled to a second electromagnetic resonator in the portable electronic device to provide non-radiative wireless power to the second resonator from the first resonator with a wireless energy transfer rate κ

,

wherein the second electromagnetic resonator is coupled to a load in the portable electronic device and movable relative to the first resonator, the second resonator having a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂),

wherein the efficiency of the wireless power transfer is at least 20% for distances D of at least 10 cm between the first and second resonators.

64. The power source of claim 63, wherein Q₁>

100.

65. The power source of claim 63, wherein (√

{square root over (Q₁Q₂)})>

100.

66. The power source of claim 63, wherein the first resonator is tunable.

67. The power source of claim 63, wherein the device is a cell phone, a computer, a robot, or a vehicle.

68. The power source of claim 63, wherein the resonant frequency f₁=ω

₁/2π

is at least 5 MHz.

69. The power source of claim 63, wherein during operation the power supply is driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.