Wireless energy transfer across variable distances

• US 8,400,024 B2
• Filed: 12/30/2009
• 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:
  US12/649,973
• Publication Number:
  US 20100102641A1
• Time in Patent Office: 1,175 Days
• Field of Search: 307/104, 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 receiving energy from an external power supply, said first resonator having a resonant frequency ω₁, an intrinsic loss rate Γ₁, and a first Q-factor Q₁=ω₁L₁/(R_1ohm+R_1rad), generating an oscillating near field region, a second electromagnetic resonator being positioned at variable distances from said first resonator and not electrically wired to said first resonator, said second resonator having a resonant frequency ω₂, an intrinsic loss rate Γ₂, and a second Q-factor Q₂=ω₂L₂/(R_2ohm+R_2rad). Electromagnetic energy may be transferred from said first resonator to said second resonator over a variable distance D that may be within the near-field region of the first resonator structure, and wherein R_1ohm>R_1rad, and R_2ohm>R_2rad.

Claims

1. A method of transferring electromagnetic energy comprising:

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

₁, an intrinsic loss rate Γ

₁, an inductance L₁, an ohmic component of resistance R_1ohm, a radiative component of resistance R_1rad, and a first Q-factor Q₁=ω

₁L₁/(R_1ohm+R_1rad), and generating a near field region comprising a temporally oscillating magnetic field;

providing a second electromagnetic resonator being positioned at variable distances from said first electromagnetic resonator and not electrically wired to said first electromagnetic resonator, said second electromagnetic resonator having a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, an inductance L₂, an ohmic component of resistance R_2ohm, a radiative component of resistance R_2rad, and a second Q-factor Q₂=ω

₂L₂/(R_2ohm+R_2rad); and

wirelessly transferring electromagnetic energy from said first electromagnetic resonator to said second electromagnetic resonator over a variable distance D as the second electromagnetic resonator moves freely within the near-field region, and wherein R_1ohm>

R_1rad, and R_2ohm>

R_2rad and at least one of Q₁ and Q₂ is greater than 100.

2. The method of claim 1, wherein the distance between the resonators is greater than 5 cm.

3. The method of claim 1, wherein the distance between the resonators is greater than 10 cm.

4. The method of claim 1, wherein the distance between the resonators is larger than a characteristic size of the smaller of the first electromagnetic resonator and the second electromagnetic resonator.

5. The method 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 method of claim 5, wherein the loops of the electrical conductors of each of the first electromagnetic resonator and the second electromagnetic resonator are in substantially the same plane.

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

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

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

10. The method of claim 1, wherein Q₁ and Q₂ are each greater than 100.

11. The method of claim 1, wherein √

{square root over (Q₁Q₂)}>

100.

12. A system of transferring electromagnetic energy comprising:

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

₁, an intrinsic loss rate Γ

₁, an inductance L₁, an ohmic component of resistance R_1ohm, a radiative component of resistance R_1rad, and a first Q-factor Q₁=ω

₁L₁/(R_1ohm+R_1rad), and generating a near field region comprising a temporally oscillating magnetic field;

a second electromagnetic resonator being positioned at variable distances from said first electromagnetic resonator and not electrically wired to said first electromagnetic resonator, said second electromagnetic resonator having a resonant frequency ω

₂, an intrinsic loss rate Γ

₂, an inductance L₂, an ohmic component of resistance R_2ohm, a radiative component of resistance R_2rad, and a second Q-factor Q₂=ω

₂L₂/(R_2ohm+R_2rad),

wherein the first and second electromagnetic resonators are coupled to wirelessly transfer electromagnetic energy from said first electromagnetic resonator to said second electromagnetic resonator over a variable distance D as the second electromagnetic resonator moves freely within the near-field region, and wherein R_1ohm>

R_1rad, and R_2ohm>

R_2rad and at least one of Q₁ and Q₂ is greater than 100.

13. The system of claim 12, wherein the distance between the resonators is greater than 5 cm.

14. The system of claim 12, wherein the distance between the resonators is greater than 10 cm.

15. The system of claim 12, wherein the distance between the resonators is larger than a characteristic size of the smaller of the first electromagnetic resonator and the second electromagnetic resonator.

16. The system of claim 12, wherein each resonator comprises an electrical conductor shaped into one or more loops wound in substantially a single plane circumscribing a substantially planar area.

17. The system of claim 16, wherein the loops of the electrical conductors of each of the first electromagnetic resonator and the second electromagnetic resonator are in substantially the same plane.

18. The system of claim 16, wherein a line drawn from the center of the first electromagnetic resonator to the center of the second electromagnetic resonator is substantially normal to the circumscribed planar area of each resonator.

19. The system of claim 16, wherein a line drawn from the center of the first electromagnetic resonator to the center of the second electromagnetic resonator is substantially parallel to the circumscribed planar area of each resonator.

20. The system of claim 16, wherein a line drawn from the center of the first electromagnetic resonator to the center of the second electromagnetic resonator forms a different angle to the surface area circumscribed by the first electromagnetic resonator than to the circumscribed planar area of each resonator.

21. The system of claim 12, wherein Q₁ and Q₂ are greater than 100.

22. The system of claim 12, wherein √

{square root over (Q₁Q₂)}>

100.