Supporting Online Material for

					                                              www.sciencemag.org/cgi/content/full/1143254/DC1




                    Supporting Online Material for

  Wireless Power Transfer via Strongly Coupled Magnetic Resonances
   André Kurs,* Aristeidis Karalis, Robert Moffatt, J. D. Joannopoulos, Peter Fisher,
                                    Marin Soljačić

        *To whom correspondence should be addressed. E-mail: akurs@mit.edu

                          Published 7 June 2007 on Science Express
                               DOI: 10.1126/science.1143254



This PDF file includes:
SOM Text
Figs. S1 to S5
Effect of using capacitively-loaded loops and lowering the op-
erating frequency on field strengths and power levels

As stated in the text, capacitively-loaded loops generate significantly lower electric fields in the
space surrounding the objects than self-resonant coils. We have performed calculations to sim-
ulate a transfer of 60W across two identical capacitively-loaded loops (6) similar in dimension
to our self-resonant coils (radius of loop 30cm, cross sectional radius of the conductor 3cm,
and distance between the loops of 2m), and calculated the maximum values of the fields and
Poynting vector 20cm away from the device loop.



 Frequency (MHz)   η Erms (V/m) Hrms (A/m) Srms (W/cm2 ) Power radiated (W)
              10 83%        185         21          0.08                 3.3
               1 60%         40         14          0.04              0.005

   At 10MHz, note the significant reduction in the electric field strength with respect to the self-
resonant coils. Lowering the operating frequency down to 1MHz further reduces the electric
field, Poynting vector, and power radiated. At 1MHz, all our fields are below IEEE safety
guidelines (18) (Erms = 614V/m, Hrms = 16.3A/m, and Srms = 0.1W/cm2 at 1MHz.)




                                                2
Figures

                       0.18
                                                                  Theory
                       0.16                                       Experiment

                       0.14

                       0.12
          κ (10e6/s)




                        0.1

                       0.08

                       0.06

                       0.04

                       0.02

                         0
                              75   100   125    150    175      200     225
                                           Distance (cm)


Figure 1: Theoretical and experimental κ as a function of distance when one of the coils is
rotated by 45% with respect to coaxial alignment.




                                             3
                         0.1
                                                                      Theory
                        0.09                                          Experiment
                        0.08

                        0.07

                        0.06
           κ (10e6/s)




                        0.05

                        0.04

                        0.03

                        0.02

                        0.01

                          0
                               100   125    150       175       200        225
                                            Distance (cm)


Figure 2: Theoretical and experimental κ as a function of distance when the coils are coplanar.




                                              4
Figure 3: 60W light-bulb being lit from 2m away. Note the obstruction in the lower image.




                                           5
Figure 4: 60W light-bulb. Alternate angle.




                    6
Figure 5: Alternative geometry.




              7

				
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