Wireless energy transfer
Disclosed is an apparatus for use in wireless energy transfer, which includes a first resonator structure configured to transfer energy non-radiatively with a second resonator structure over a distance greater than a characteristic size of the second resonator structure. The non-radiative energy transfer is mediated by a coupling of a resonant field evanescent tail of the first resonator structure and a resonant field evanescent tail of the second resonator structure.
1. A wireless power system comprising:
a source resonator and a power supply coupled to the source resonator to provide power to the source resonator, the source resonator having a resonant frequency ω 1 , an intrinsic loss rate Γ 1 , and an intrinsic quality factor Q 1 =ω 1 /(2Γ 1 ); and
a device resonator and a load coupled to the device resonator to receive power from the device resonator, the device resonator having a resonant frequency ω 2 , an intrinsic loss rate Γ 2 , and an intrinsic quality factor Q 2 =ω 2 /(2Γ 2 ),
wherein the source resonator and the device resonator are configured to resonantly and wirelessly couple electromagnetic power from the source resonator to the device resonator over a range of distances D between the source resonator and the device resonator using non-radiative electromagnetic induction having a coupling coefficient κ, and wherein the intrinsic loss rates satisfy κ/√{square root over (Γ 1 Γ 2 )}>2 over the range of distances D between the source resonator and the device resonator,
wherein Q 1 >100 and Q 2 >100, and
further comprising a current probe configured to measure a current in at least one of the resonators.
2. The wireless power system of claim 1 , further comprising a monitor configured to measure an efficiency of power coupled to the load from the source resonator using information from the current measurement.
3. The wireless power system of claim 2 , further comprising a frequency adjuster configured to adjust a frequency of the wireless energy transfer based on the measurement by the monitor.
4. The wireless power system of claim 3 , wherein the frequency adjuster is configured to adjust the resonant frequency of the device resonator.
5. The wireless power system of claim 2 , wherein the resonators wirelessly exchange information based on the measurement by the monitor.
6. The wireless power system of claim 1 , further comprising a portable electronic device comprising the device resonator and the load, wherein f 1 =ω 1 /(2π) and f 2 =ω 2 /(2π), and f 1 and f 2 , are between 1 MHz and 10 MHz, wherein each intrinsic loss rate comprises a resistive component and a radiative component, and wherein the power provided to the load from the device resonator is greater than about 1 Watt.
7. The wireless power system of claim 6 , wherein the portable electronic device is a cell phone, a computer, or a robot.
8. The wireless power system of claim 6 , wherein the device resonator has a characteristic size that is less than 10 cm and comprises at least one loop of conductive material having a width less than 2 mm.
9. The wireless power system of claim 6 , wherein the resonators each have a characteristic size, and wherein the characteristic size of the device resonator differs from that of the source resonator.
10. The wireless power system of claim 1 , wherein Q 1 >200 and Q 2 >200.
11. The wireless power system of claim 10 , wherein the load is configured to provide power to a vehicle, wherein the intrinsic loss rates satisfy κ/√{square root over (Γ 1 Γ 2 )}>5 over the range of distances D, and wherein the power provided to the load from the device resonator is greater than about 10 Watt.
12. The wireless power system of claim 11 , wherein f 1 =ω 1 /(2π) and f 2 =ω 2 /(2π), and f 1 and f 2 , are between 10 kHz and 1 MHz.
13. The wireless power system of claim 11 , where the device resonator has a characteristic size that is less than 30 cm.
14. The wireless power system of claim 1 , wherein the device resonator is configured to be movable relative to the source resonator over the range of distances D between the source resonator and the device resonator.
15. The wireless power system of claim 1 , wherein each resonator comprises at least one loop of conductive material.
16. The wireless power system of claim 15 , wherein the conducting loop in each of the source resonator and the device resonator is capacitively loaded.
17. The wireless power system of claim 15 , wherein the conducting loop in each of the source resonator and the device resonator is self-resonant.
18. A method for providing wireless power to a load, the method comprising:
providing a source resonator and a power supply coupled to the source resonator to provide power to the source resonator, the source resonator having a resonant frequency an intrinsic loss rate Γ 1 , and an intrinsic quality factor Q 1 =ω 1 /(2Γ 1 ); and
providing a device resonator coupled to the load to provide power to the load, the device resonator having a resonant frequency ω 2 , an intrinsic loss rate Γ 2 , and an intrinsic quality factor Q 2 =ω 2 (2Γ 2 ),
resonantly and wirelessly coupling electromagnetic power from the source resonator to the device resonator using non-radiative electromagnetic induction having a coupling coefficient κ, and wherein the intrinsic loss rates satisfy κ/√{square root over (Γ 1 Γ 2 )}>2 over a range of distances D between the source resonator and the device resonator,
wherein Q 1 >100 and Q 2 >100, and
further comprising measuring a current in at least one of the resonators.
19. The wireless power method of claim 18 , further comprising measuring an efficiency of power coupled to the load from the source resonator using information from the current measurement.
20. The wireless power method of claim 19 , further comprising adjusting a frequency of the wireless energy transfer based on the efficiency measurement.
21. The wireless power method of claim 20 , wherein the adjusted frequency is the resonant frequency of the device resonator.
22. The wireless power method of claim 18 , further comprising wirelessly exchanging information between the resonators based on the measurement.
23. The wireless power method of claim 18 , wherein the device resonator and the load are part of a portable electronic device, wherein f 1 =ω1/(2π) and f 2 =ω 2 /(2π), and f 1 and f 2 , are between 1 MHz and 10 MHz, wherein each intrinsic loss rate comprises a resistive component and a radiative component, and wherein the power provided to the load from the device resonator is greater than about 1 Watt.
24. The wireless power method of claim 23 , wherein the portable electronic device is a cell phone, a computer, or a robot.
25. The wireless power method of claim 23 , wherein the device resonator has a characteristic size that is less than 10 cm and comprises at least one loop of conductive material having a width less than 2 mm.
26. The wireless power method of claim 23 , wherein the resonators each have a characteristic size, and wherein the characteristic size of the device resonator differs from that of the source resonator.
27. The wireless power method of claim 18 , wherein Q 1 >200 and Q 2 >200.
28. The wireless power method of claim 27 , wherein the load is configured to provide power to a vehicle, wherein the intrinsic loss rates satisfy κ/√{square root over (Γ 1 Γ 2 )}>5 over the range of distances D, and wherein the power provided to the load from the device resonator is greater than about 10 Watt.
29. The wireless power method of claim 28 , wherein f 1 =ω 1 /(2π) and f 2 =ω 2 /(2π), and f 1 and f 2 , are between 10 kHz and 1 MHz.
30. The wireless power method of claim 28 , where the device resonator has a characteristic size that is less than 30 cm.
31. The wireless power method of claim 18 , wherein the device resonator is configured to be movable relative to the source resonator over the range of distances D between the source resonator and the device resonator.
32. The wireless power method of claim 18 , wherein each resonator comprises at least one loop of conductive material.
33. The wireless power method of claim 32 , wherein the conducting loop in each of the source resonator and the device resonator is capacitively loaded.
34. The wireless power method of claim 32 , wherein the conducting loop in each of the source resonator and the device resonator is self-resonant.