Wireless energy transfer across a distance to a moving device

• US 8,772,972 B2
• Filed: 12/30/2009
• Issued: 07/08/2014
• 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:
  US12/649,852
• Publication Number:
  US 20100133920A1
• Time in Patent Office: 1,651 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 coupled to an energy source generating an oscillating near field region, and a second resonator optionally coupled to an energy drain and moving freely within the near field region of the first resonator. The first resonator and the second resonator may be coupled to transfer electromagnetic energy from said first resonator to said second resonator as the second resonator moves freely within the near field region, and where the region may include distances greater than the characteristic size of the smaller of the first resonator and the second resonator.

Claims

1. A system, comprising:

a first resonator configured to be coupled to an energy source to generate a near field region comprising a temporally oscillating magnetic field; and

a second resonator configured to move freely within the near field region of the first resonator,

wherein the first resonator and the second resonator are configured to be resonantly coupled to wirelessly transfer electromagnetic energy from said first resonator to said second resonator as the second resonator moves freely within the near field region,

and where the region includes distances D greater than the characteristic size of each of the first resonator and the second resonator,

wherein the first resonator has a resonant frequency ω

₁, an intrinsic loss rate Γ

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

₁/(2Γ

₁),

wherein the second resonator has a resonant frequency ω

₂, an intrinsic loss rate Γ

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

₂/(2Γ

₂), and

wherein Q₁>

100 and Q₂>

100, and

wherein the distances D for the near-field wireless energy transfer are less than the wavelengths λ

₁=c/2π

ω

₁ and λ

₂=c/2π

ω

₂ corresponding to the resonant frequencies ω

₁ and ω

₂, respectively, where c is the speed of light.

2. 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.

3. The system of claim 2, wherein the loops of the electrical conductors of each of the first and second resonators are in substantially the same plane.

4. The system of claim 2, 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.

5. The system of claim 2, 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.

6. The system of claim 2, 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.

7. The system of claim 1, wherein the efficiency of the wireless transfer of electromagnetic energy from said first resonator to said second resonator as the second resonator moves freely within the near field region is at least 20%.

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

9. The system of claim 8, wherein the energy drain comprises a robot, vehicle, computer, cell phone, or a portable electronic device.

10. The system of claim 1, 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.

11. The system of claim 10, 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.

12. The system of claim 10, 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.

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 1, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.2 for a range of the distances D greater than the characteristic size of each of the first resonator and the second resonator in the near-field region, wherein κ

is the wireless energy transfer rate.

17. The system of claim 1, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

1 for a range of the distances D greater than the characteristic size of each of the first resonator and the second resonator in the near-field region, wherein κ

is the wireless energy transfer rate.

18. A method, comprising:

providing a first resonator coupled to an energy source and generating a near field region comprising a temporally oscillating magnetic field; and

providing a second resonator coupled to an energy drain and moving freely within the near field region of the first resonator,

wherein the first resonator and the second resonator are resonantly coupled to transfer electromagnetic energy from said first resonator to said second resonator as the second resonator moves freely within the near field region,

and where the region includes distances D greater than the characteristic size of each of the first resonator and the second resonator,

wherein the first resonator has a resonant frequency ω

₁, an intrinsic loss rate Γ

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

₁/(2Γ

₁),

wherein the second resonator has a resonant frequency ω

₂, an intrinsic loss rate Γ

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

₂/(2Γ

₂), and

wherein Q₁>

100 and Q₂>

100, and

wherein the distances D for the near-field wireless energy transfer are less than the wavelengths λ

₁=c/2π

ω

₁ and λ

₂=c/2π

ω

₂ corresponding to the resonant frequencies ω

₁ and ω

₂, respectively, where c is the speed of light.

19. 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.

20. The method of claim 19, wherein the loops of the electrical conductors of each of the first and second resonators are in substantially the same plane.

21. The method of claim 19, 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.

22. The method of claim 19, 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.

23. The method of claim 19, 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.

24. The method of claim 18, wherein the efficiency of the wireless transfer of electromagnetic energy from said first resonator to said second resonator as the second resonator moves freely within the near field region is at least 20%.

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

26. The method of claim 18, wherein the energy source is coupled to the first resonator and an energy drain is coupled to the second resonator to provide useful power to the energy drain, and wherein the energy source provides 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.

27. The method of claim 26, wherein the energy source provides energy to the first resonator at a rate that substantially minimizes the energy stored in the first resonator and the second resonator.

28. The method of claim 26, wherein the energy source provides 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.

29. The method of claim 18, wherein Q₁>

200 and Q₂>

200.

30. The method of claim 18, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

0.2 for a range of the distances D greater than the characteristic size of each of the first resonator and the second resonator in the near-field region, wherein κ

is the wireless energy transfer rate.

31. The method of claim 18, wherein κ

/√

{square root over (Γ

₁Γ

₂)}>

1 for a range of the distances D greater than the characteristic size of each of the first resonator and the second resonator in the near-field region, wherein κ

is the wireless energy transfer rate.