Wireless non-radiative energy transfer

• US 8,076,800 B2
• Filed: 03/31/2009
• Issued: 12/13/2011
• 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:
  US12/415,655
• Publication Number:
  US 20090195333A1
• Time in Patent Office: 987 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, comprising:

a source resonator configured to be coupled to an energy source; and

a second resonator located a distance from the source resonator;

wherein the source resonator and the second resonator are coupled to provide resonant non-radiative wireless energy transfer between the source resonator and the second resonator and wherein at least one resonator is a tunable resonator,

wherein the source resonator has a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁), the second resonator has a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂), and at least one of Q₁ and Q₂ is greater than 100.

2. The system of claim 1, wherein the tunable resonator is a capacitively-loaded conducting-wire loop.

3. The system of claim 1, wherein the tunable resonator is tuned through changes in its geometry.

4. The system of claim 1, wherein the resonators wirelessly transfer energy at a continuous-wave frequency of the normal mode for the resonators that has a larger radiation-Q.

5. The system of claim 1, wherein the resonators are electromagnetic resonators.

6. The system of claim 5, wherein (√

{square root over (Q₁Q₂)})>

100.

7. The system of claim 5, wherein the rate of the wireless energy transfer rate is κ

, the second resonator has a characteristic size L₁, and 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.

8. The system of claim 5, wherein the second resonator has a characteristic size L₂ and the efficiency of the wireless energy transfer is at least 20% for at least some distances D between the source and second resonators satisfying D/L₂>

1.

9. The system of claim 5, wherein the efficiency of the wireless energy transfer is at least 20% for at least some distances D between the source and second resonators including 10 cm.

10. The system of claim 5, further comprising the energy source and a load coupled to the second resonator, and wherein during operation the energy source and the load are driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.

11. The system of claim 5, wherein the source resonator and the second resonator are electromagnetic resonators comprising a capacitance and an inductance.

12. The system of claim 5, wherein the resonant frequencies f₁=ω

₁/2π and

f₂=ω

₂/2π

are each at least 5 MHz.

13. The system of claim 5, further comprising an additional resonator coupled to the source resonator to provide resonant non-radiative wireless energy transfer between the source resonator and the additional resonator.

26. The system of claim 1, wherein the source resonator and the second resonator are movable relative to one another to a define a variable distance between them.

14. A system, comprising:

a source resonator configured to be coupled to an energy source; and

a second resonator located a distance from the source resonator;

wherein the source resonator and the second resonator are coupled to provide resonant non-radiative wireless energy transfer between the source resonator and the second resonator,

wherein at least one resonator is a tunable resonator, and

wherein at least one resonator is a high-Q resonator.

15. The system of claim 14, wherein the high-Q resonator has a resonant frequency ω

, an intrinsic loss rate Γ

, and a first Q-factor Q=ω

/(2Γ

)>

100.

16. The system of claim 14, wherein the source resonator has a resonant frequency ω

₁, an intrinsic loss rate Γ

₁, and a first Q-factor Q₁=ω

₁/(2Γ

₁), the second resonator has a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, and a second Q-factor Q₂=ω

₂/(2Γ

₂), and wherein (√

{square root over (Q₁Q₂)})>

100.

17. The system of claim 14, wherein the tunable resonator is tuned through changes in its geometry.

18. The system of claim 14, wherein the resonators wirelessly transfer energy at a continuous-wave frequency of the normal mode for the resonators that has a larger radiation-Q.

19. The system of claim 14, wherein the rate of the wireless energy transfer rate is κ

, the second resonator has a characteristic size L₁, and the resonators to 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.

20. The system of claim 14, wherein the second resonator has a characteristic size L₂ and the efficiency of the wireless energy transfer is at least 20% for at least some distances D between the source and second resonators satisfying D/L₂>

1.

21. The system of claim 14, wherein the efficiency of the wireless energy transfer is at least 20% for at least some distances D between the source and second resonators including 10 cm.

22. The system of claim 14, further comprising the energy source and a load coupled to the second resonator, and wherein during operation the energy source and the load are driven to increase the ratio of useful-to-lost power for the wireless energy transfer rate κ

.

23. The system of claim 14, wherein the source resonator and the second resonator are electromagnetic resonators comprising a capacitance and an inductance.

24. The system of claim 14, wherein the resonant frequencies f₁=ω

₁/2π and

f₂=ω

₂/2π

are each at least 5 MHz.

25. The system of claim 14, further comprising an additional resonator coupled to the source resonator to provide resonant non-radiative wireless energy transfer between the source resonator and the additional resonator.

27. The system of claim 14, wherein the source resonator and the second resonator are movable relative to one another to a define a variable distance between them.