Wireless energy transfer with high-Q sub-wavelength resonators

• US 8,400,021 B2
• Filed: 12/16/2009
• Issued: 03/19/2013
• 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): Fleming, Fritz M
• Application Number:
  US12/639,972
• Publication Number:
  US 20100123355A1
• Time in Patent Office: 1,189 Days
• Field of Search: 307/104, 333/195, 320/108
• 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

Described herein are embodiments of transferring electromagnetic energy that includes a first electromagnetic resonator structure receiving energy from an external power supply, said first resonator structure may have a first mode with a resonant frequency ω₁, an intrinsic loss rate Γ₁, and a first Q-factor Q₁=ω₁L₁/R_1ohm+R_1rad). A second electromagnetic resonator structure being positioned distal from said first resonator structure and not electrically wired to the first resonator structure, said second resonator structure having a second mode with a resonant frequency ω₂, an intrinsic loss rate Γ₂, and a second Q-factor Q₂=ω₂L₂/(R_2ohm+R_2rad). The electromagnetic energy may be transferred from said first resonator structure to said second resonator structure over a distance D that is smaller than each of the resonant wavelengths λ₁ and λ₂ corresponding to the resonant frequencies ω₁ and ω₂, respectively, where the characteristic sizes of the resonator structures are less than the resonant wavelengths and where Q1>100, Q2>100, R_1ohm>R_1rad, and R_2ohm>R_2rad.

Claims

1. A system of transferring electromagnetic energy comprising:

a first electromagnetic resonator receiving energy from a power supply, said first electromagnetic resonator having a first mode with a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, an inductance L₁, and a first Q-factor Q₁=ω

₁L₁/(R_1ohm+R_1rad), wherein R_1ohm is the ohmic component of resistance in the first electromagnetic resonator and R_1rad is the radiative component of resistance in the first resonator;

a second electromagnetic resonator being positioned distal from said first electromagnetic resonator and not electrically wired to the first electromagnetic resonator, said second electromagnetic resonator having a second mode with a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and inductance L₂, and a second Q-factor Q₂=ω

₂L₂/(R_2ohm+R_2rad), wherein R_2ohm is the ohmic component of resistance in the second electromagnetic resonator and R_2rad is the radiative component of resistance in the second electromagnetic resonator; and

wherein electromagnetic energy is wirelessly transferred from said first electromagnetic resonator to said second electromagnetic resonator over a distance D that is smaller than each of the resonant wavelengths λ

₁ and λ

₂ corresponding to the resonant frequencies ω

₁ and ω

₂, respectively,

wherein √

{square root over (Q₁Q₂)}>

100, R_1ohm>

R_1rad, and R_2ohm>

R_2rad.

2. The system of claim 1, further comprising an energy drain coupled to the second electromagnetic resonator.

3. The system of claim 2, wherein the energy drain comprises a robot, vehicle, computer, cell phone, or a portable electronic device.

4. The system of claim 1, wherein Q₁>

100.

5. The system of claim 1, wherein Q₂>

100.

6. The system of claim 1, wherein Q₁>

100 and Q₂>

100.

7. The system of claim 1, further comprising a third electromagnetic resonator, coupled to an energy drain, located at a variable distance from the first electromagnetic resonator, and wherein the first electromagnetic resonator and the third electromagnetic resonator are coupled to wirelessly transfer electromagnetic energy from the first electromagnetic resonator to the third electromagnetic resonator.

8. The system of claim 7, further comprising the energy drain coupled to the third electromagnetic resonator.

9. The system of claim 1, further comprising a third electromagnetic resonator, coupled to another power supply, located at a variable distance from the second electromagnetic resonator, and wherein the third electromagnetic resonator and the second electromagnetic resonator are coupled to wirelessly transfer electromagnetic energy from the third electromagnetic resonator to the second electromagnetic resonator.

10. The system of claim 1, wherein at least one of the electromagnetic resonators is a tunable electromagnetic resonator.

11. The system of claim 1, wherein the electromagnetic resonators are movable relative to one another and wherein the wireless energy transfer occurs over a range of distances.

12. The system of claim 11, wherein the range of distances includes 5 cm.

13. The system of claim 11, wherein the range of distances includes 10 cm.

14. The system of claim 11, wherein the range of distances includes 30 cm.

15. The system of claim 11, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.2 over the range of distances.

16. The system of claim 15, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.5 over the range of distances.

17. The system of claim 15, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

1 over the range of distances.

18. The system of claim 11, wherein an efficiency of the wireless energy transfer is at least 20% over the range of distances.

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

₁/2π and

f₂=ω

₂/2π

are each at least 5 MHz.

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

21. The system of claim 1, wherein an energy drain is coupled to the second electromagnetic resonator, and wherein the power supply and the energy drain are configured to be driven to increase a ratio of useful-to-lost power for varying wireless energy transfer rates κ

between the first electromagnetic resonator and the second electromagnetic resonator.

22. The system of claim 1, wherein the first electromagnetic resonator and second electromagnetic resonator are configured to be adjustably tuned to increase a ratio of useful-to-lost power for varying wireless energy transfer rates κ

between the first electromagnetic resonator and the second electromagnetic resonator.

23. The system of claim 1, wherein the first electromagnetic resonator and the second electromagnetic resonator have different characteristic sizes.

24. The system of claim 1, wherein characteristic sizes of the electromagnetic resonators are less than the resonant wavelengths of the electromagnetic resonators, respectively.

25. A method of transferring electromagnetic energy comprising:

providing a first electromagnetic resonator receiving energy from a power supply, said first electromagnetic resonator having a first mode with a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, an inductance L₁, and a first Q-factor Q₁=ω

₁L₁/(R_1ohm+R_1rad), wherein R_1ohm is the ohmic component of resistance in the first electromagnetic resonator and R_1rad is the radiative component of resistance in the first electromagnetic resonator;

providing a second electromagnetic resonator being positioned distal from said first electromagnetic resonator and not electrically wired to the first electromagnetic resonator, said second electromagnetic resonator having a second mode with a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and inductance L₂, and a second Q-factor Q₂=ω

₂L₂/(R_2ohm+R_2rad), wherein R_2ohm is the ohmic component of resistance in the second electromagnetic resonator and R_2rad is the radiative component of resistance in the second electromagnetic resonator; and

transferring electromagnetic energy wirelessly from said first electromagnetic resonator to said second electromagnetic resonator over a distance D that is smaller than each of the resonant wavelengths λ

₁ and λ

₂ corresponding to the resonant frequencies ω

₁ and ω

₂, respectively,

wherein √

{square root over (Q₁Q₂)}>

100, R_1ohm>

R_1rad, and R_2ohm>

R_2rad.

26. The method of claim 25, wherein an energy drain is coupled to the second electromagnetic resonator.

27. The method of claim 26, wherein the energy drain comprises a robot, vehicle, computer, cell phone, or a portable electronic device.

28. The method of claim 25, wherein Q₁>

100.

29. The method of claim 25, wherein Q₂>

100.

30. The method of claim 25, wherein Q₁>

100 and Q₂>

100.

31. The method of claim 25, wherein a third electromagnetic resonator, coupled to an energy drain, is located at a variable distance from the first electromagnetic resonator, and wherein the first electromagnetic resonator and the third electromagnetic resonator are coupled to wirelessly transfer electromagnetic energy from the first electromagnetic resonator to the third electromagnetic resonator.

32. The method of claim 31, wherein the energy drain is coupled to the third electromagnetic resonator.

33. The method of claim 25, wherein a third electromagnetic resonator, coupled to another power supply, is located at a variable distance from the second electromagnetic resonator, and wherein the third electromagnetic resonator and the second electromagnetic resonator are coupled to wirelessly transfer electromagnetic energy from the third electromagnetic resonator to the second electromagnetic resonator.

34. The method of claim 25, wherein at least one of the electromagnetic resonators is a tunable resonator.

35. The method of claim 25, wherein the electromagnetic resonators are movable relative to one another and wherein the wireless energy transfer occurs over a range of distances.

36. The method of claim 35, wherein the range of distances includes 5 cm.

37. The method of claim 35, wherein the range of distances includes 10 cm.

38. The method of claim 35, wherein the range of distances includes 30 cm.

39. The method of claim 35, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.2 over the range of distances.

40. The method of claim 39, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.5 over the range of distances.

41. The method of claim 39, wherein κ

/√

{square root over (Γ

₁Γ

₂)}1 over the range of distances.

42. The method of claim 35, wherein an efficiency of the wireless energy transfer is at least 20% over the range of distances.

43. The method of claim 25, wherein resonant frequencies f₁=ω

₁/2π and

f₂=ω

₂/2π

are each at least 5 MHz.

44. The method of claim 25, wherein a feedback mechanism is coupled to at least one of the electromagnetic resonators to correct for frequency detuning.

45. The method of claim 25, wherein an energy drain is coupled to the second electromagnetic resonator, and wherein the power supply and the energy drain are driven to increase a ratio of useful-to-lost power for varying wireless energy transfer rates κ

between the first electromagnetic resonator and the second electromagnetic resonator.

46. The method of claim 25, wherein the first electromagnetic resonator and second electromagnetic resonator are adjustably tuned to increase a ratio of useful-to-lost power for varying wireless energy transfer rates κ

between the first electromagnetic resonator and the second electromagnetic resonator.

47. The method of claim 25, wherein the first electromagnetic resonator and the second electromagnetic resonator have different characteristic sizes.

48. The method of claim 25, wherein characteristic sizes of the electromagnetic resonators are less than the resonant wavelengths of the electromagnetic resonators, respectively.