Wireless energy transfer over a distance at high efficiency

• US 8,395,283 B2
• Filed: 12/16/2009
• Issued: 03/12/2013
• 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:
  US12/639,961
• Publication Number:
  US 20100127573A1
• Time in Patent Office: 1,182 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 5/79 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 a source resonator optionally coupled to an energy source, and a second resonator, optionally coupled to an energy drain that may be located a distance from the source resonator. The source resonator and the second resonator may be coupled to provide κ/sqrt(Γ₁Γ₂)>0.2 via near-field wireless energy transfer among the source resonator and the second resonator over distances up to at least the characteristic size of a resonator.

Claims

1. A system, comprising:

a source resonator coupled to an energy source; and

a second resonator, coupled to an energy drain, located a distance from the source resonator,

wherein the source resonator and the second resonator are coupled to provide κ

/√

{square root over (Γ

₁Γ

₂)}>

0.2 via near-field wireless energy transfer among the source resonator and the second resonator over distances up to at least the characteristic size of at least one of the source resonator and the second resonator, wherein κ

is the wireless energy transfer rate, Γ

₁ is the intrinsic loss rate of the source resonator, and Γ

₂ is the intrinsic loss rate of the second resonator.

2. The system of claim 1, wherein the energy drain comprises a robot, vehicle, computer, cell phone, or a portable electronic device.

3. The system of claim 1, wherein at least one of the resonators has a Q-factor Q_i>

100.

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

5. The system of claim 1, wherein at least 10 Watts of power is transferred over the distances.

6. The system of claim 1, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.5 over the distances.

7. The system of claim 1, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

1 over the distances.

8. The system of claim 1, wherein each resonator comprises an inductive element and a capacitive element.

9. The system of claim 1, wherein the distances can vary to values greater than at least several times the characteristic size of at least one of the source resonator and the second resonator.

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

11. The system of claim 1, wherein the distances include 10 cm.

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

13. The system of claim 1, wherein the resonators are movable relative to one another.

14. The system of claim 1, wherein the resonators have respective resonant frequencies f₁=ω

₁/2π and

f₂=ω

₂/2π

which are each at least 5 MHz.

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

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

.

17. The system of claim 1, wherein the source resonator and second resonator are configured to be adjustably tuned to increase the ratio of useful-to-lost power for varying wireless energy transfer rates x over the distances.

18. The system of claim 1, wherein the source resonator has a Q-factor Q₁ and the second resonator has a Q-factor Q₂, and wherein √

{square root over (Q₁Q₂)}>

100.

19. The system of claim 1, wherein the source resonator has a Q-factor Q₁>

100 and the second resonator has a Q-factor Q₂>

100.

20. The system of claim 1, wherein the source resonator and the second resonator have different characteristic sizes.

21. The method of claim 1, wherein the source resonator and the second resonator have different characteristic sizes.

22. A method, comprising:

providing a source resonator coupled to an energy source and a second resonator, wherein the second resonator is coupled to an energy drain and located a distance from the source resonator,

wherein the source resonator and the second resonator are coupled to provide κ

/√

{square root over (Γ

₁Γ

₂)}>

0.2 via near-field wireless energy transfer among the source resonator and the second resonator over distances up to at least the characteristic size of at least one of the source resonator and the second resonator, wherein κ

is the wireless energy transfer rate, Γ

₁ is the intrinsic loss rate of the source resonator, and Γ

₂ is the intrinsic loss rate of the second resonator.

23. The method of claim 22, wherein the energy drain comprises a robot, vehicle, computer, cell phone, or a portable electronic device.

24. The method of claim 22, wherein at least one of the resonators has a Q-factor Q_i>

100.

25. The method of claim 22, wherein at least one of the resonators is tunable.

26. The method of claim 22, wherein at least 10 Watts of power is transferred over the distances.

27. The method of claim 22, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.5 over the distances.

28. The method of claim 22, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

1 over the distances.

29. The method of claim 22, wherein each resonator comprises an inductive element and a capacitive element.

30. The method of claim 22, wherein the distances can vary to values greater than at least several times the characteristic size of at least one of the source resonator and the second resonator.

31. The method of claim 22, wherein the distances include 5 cm.

32. The method of claim 22, wherein the distances include 10 cm.

33. The method of claim 22, wherein the distances include 30 cm.

34. The method of claim 22, wherein the resonators are movable relative to one another.

35. The method of claim 22, wherein the resonators have respective resonant frequencies f₁=ω

₁/2π and

f₂=ω

₂/2π

which are each at least 5 MHz.

36. The method of claim 22, wherein a feedback mechanism is coupled to at least one of the resonators to correct for detuning.

37. The method of claim 22, wherein the energy source is coupled to the source resonator and the energy drain is coupled to the second resonator, and wherein the energy source and energy drain are driven to increase the ratio of useful-to-lost power for varying wireless energy transfer rates K.

38. The method of claim 22, wherein the source resonator and second resonator are adjustably tuned to increase the ratio of useful-to-lost power for varying wireless energy transfer rates x over the distances.

39. The method of claim 22, wherein the source resonator has a Q-factor Q₁ and the second resonator has a Q-factor Q₂, and wherein √

{square root over (Q₁Q₂)}>

100.

40. The method of claim 22, wherein the source resonator has a Q-factor Q₁>

100 and the second resonator has a Q-factor Q₂>

100.