Wireless energy transfer over variable distances between resonators of substantially similar resonant frequencies

• US 8,760,008 B2
• Filed: 12/30/2009
• Issued: 06/24/2014
• 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:
  US12/649,777
• Publication Number:
  US 20100133918A1
• Time in Patent Office: 1,637 Days
• Field of Search: 307/104
• 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 a first resonator, with a resonant frequency f1, optionally coupled to an energy source; and a second resonator, with a resonant frequency f2, optionally coupled to an energy drain, located a variable distance from the first resonator. The first resonator and the second resonator may be coupled to provide near-field wireless energy transfer among the first resonator and the second resonator, and where f1 may be approximately equal to f2 and both f1 and f2 may be less than 400 MHz.

Claims

1. A system, comprising:

a first resonator having a resonant frequency ω

₁ and an intrinsic loss rate Γ

₁, and capable of storing electromagnetic energy with a high intrinsic quality factor Q₁=ω

₁/(2Γ

₁), and configured to be coupled to an energy source; and

a second resonator having a resonant frequency ω

₂ and an intrinsic loss rate Γ

₂, and capable of storing electromagnetic energy with a high intrinsic quality factor Q₂=ω

₂/(2Γ

₂), located a variable distance D from the first resonator;

wherein the first resonator and the second resonator are configured to be resonantly coupled to provide near-field wireless energy transfer among the first resonator and the second resonator over the variable distance D when the first resonator is coupled to the energy source;

wherein the variable distance D is no more than ten times the characteristic size L₂ of the second resonator and wherein the efficiency of the wireless energy transfer is at least 20%, and

wherein Q₁>

100 and Q₂>

100.

2. The system of claim 1, wherein the variable distance includes distances greater than 5 cm.

3. The system of claim 1, wherein the variable distance includes distances greater than 10 cm.

4. The system of claim 1, wherein the variable distance between the resonators is larger than the characteristic size L₂ of the second resonator.

5. The system of claim 1, wherein each resonator comprises an electrical conductor shaped into one or more loops wound in substantially a single plane circumscribing a substantially planar area.

6. The system of claim 5, wherein the loops of the electrical conductors of each of the first and second resonators are in substantially the same plane.

7. The system of claim 5, wherein a line drawn from the center of the first resonator to the center of the second resonator is substantially normal to the circumscribed planar area of each resonator.

8. The system of claim 5, wherein a line drawn from the center of the first resonator to the center of the second resonator is substantially parallel to the circumscribed planar area of each resonator.

9. The system of claim 5, wherein a line drawn from the center of the first resonator to the center of the second resonator forms a different angle to the surface area circumscribed by the first resonator than to the circumscribed planar area of each resonator.

10. The system of claim 1, wherein f₁=ω

₁/(2π

) is approximately equal to f₂=ω

₂/(2π

) and both f₁ and f₂ are less than or equal to 17 MHz.

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

12. The system of claim 11, wherein the energy drain comprises a robot, vehicle, computer, cell phone, or a portable electronic device.

13. The system of claim 1, wherein f₁=ω

₁/(2π

) and f₂=ω

₂/(2π

), and each of f₁ and f₂ is between about 5 MHz and 380 MHz.

14. The system of claim 1, wherein each intrinsic loss rate comprises a resistive component and a radiative component.

15. The system of claim 1, wherein Q₁>

200 and Q₂>

200.

16. The system of claim 15, further comprising the energy source coupled to the first resonator and a vehicle having the second resonator, and wherein the system is configured to provide wireless power to the vehicle from the first resonator to the second resonator.

17. The system of claim 1, further comprising the energy source coupled to the first resonator and a vehicle having the second resonator, and wherein the system is configured to provide wireless power to the vehicle from the first resonator to the second resonator.

18. A method, comprising:

providing a first resonator having a resonant frequency ω

₁ and an intrinsic loss rate Γ

₁, and capable of storing electromagnetic energy with a high intrinsic quality factor Q₁=ω

₁/(2Γ

₁), coupled to an energy source; and

providing a second resonator having a resonant frequency ω

₂ and an intrinsic loss rate Γ

₂, and capable of storing electromagnetic energy with a high intrinsic quality factor Q₂=ω

₂/(2Γ

₂), located a variable distance D from the first resonator;

wherein the first resonator and the second resonator are resonantly coupled to provide near-field wireless energy transfer among the first resonator and the second resonator over the variable distance D;

wherein the variable distance D is no more than ten times the characteristic size L₂ of the second resonator and wherein the efficiency of the wireless energy transfer is at least 20%, and

wherein Q₁>

100 and Q₂>

100.

19. The method of claim 18, wherein the variable distance between the resonators includes distances greater than 5 cm.

20. The method of claim 18, wherein the variable distance between the resonators includes greater than 10 cm.

21. The method of claim 18, wherein the variable distance between the resonators is larger than the characteristic size L₂ of second resonator.

22. The method of claim 18, wherein each resonator comprises an electrical conductor shaped into one or more loops wound in substantially a single plane circumscribing a substantially planar area.

23. The method of claim 22, wherein the loops of the electrical conductors of each of the first and second resonators are in substantially the same plane.

24. The method of claim 22, wherein a line drawn from the center of the first resonator to the center of the second resonator is substantially normal to the circumscribed planar area of each resonator.

25. The method of claim 22, wherein a line drawn from the center of the first resonator to the center of the second resonator is substantially parallel to the circumscribed planar area of each resonator.

26. The method of claim 22, wherein a line drawn from the center of the first resonator to the center of the second resonator forms a different angle to the surface area circumscribed by the first resonator than to the circumscribed planar area of each resonator.

27. The method of claim 18, wherein Q₁>

200 and Q₂>

200.

28. The method of claim 27, wherein a vehicle carries the second resonator, and wherein the method provides wireless power to the vehicle from the first resonator to the second resonator.

29. The method of claim 18, wherein a vehicle carries the second resonator, and wherein the method provides wireless power to the vehicle from the first resonator to the second resonator.

30. The method of claim 18, wherein f₁=ω

₁/(2π

) is approximately equal to f₂=ω

₂/(2π

) and both f₁ and f₂ are less than or equal to 17 MHz.

31. The method of claim 18, wherein each intrinsic loss rate comprises a resistive component and a radiative component.

32. A system, comprising:

a first resonator having a resonant frequency ω

₁ and an intrinsic loss rate Γ

₁, and capable of storing electromagnetic energy with a high intrinsic quality factor Q₁=ω

₁/(2Γ

₁), and configured to be coupled to an energy source; and

a second resonator having a resonant frequency ω

₂ and an intrinsic loss rate Γ

₂, and capable of storing electromagnetic energy with a high intrinsic quality factor Q₂=ω

₂/(2Γ

₂), located a variable distance D from the first resonator;

wherein the first resonator and the second resonator are configured to be coupled to provide near-field wireless energy transfer among the first resonator and the second resonator over the variable distance D when the first resonator is coupled to the energy source;

wherein the variable distance D includes distances greater than the characteristic size L₂ of the second resonator and wherein the efficiency of the wireless energy transfer is at least 20%, and

wherein Q₁>

100 and Q₂>

100,

further comprising the energy source configured to be coupled to the first resonator and an energy drain configured to be coupled to the second resonator to provide useful power to the energy drain, and wherein the energy source is configured to provide energy to the first resonator at a rate that varies with a rate of wireless energy transfer κ

between the first resonator and the second resonator.

33. The system of claim 32, wherein the energy source is configured to provide energy to the first resonator at a rate that substantially minimizes the energy stored in the first resonator and the second resonator.

34. The system of claim 32, wherein the energy source is configured to provide energy to the first resonator at a rate that substantially maximizes a ratio of the useful power to lost power from the energy source to the energy drain.