Decius wrote: Need feedback from nerds...
Here are some pointers: A good place to start is with the MIT press release, which describes the work of Marin Soljačić. On his web site, he points to a paper describing the theory of Wireless Power Transfer; a simplified explanation is also provided in an accompanying press release. The MIT team has also conducted successful experiments in wireless power transfer, reported today in Science: Using self-resonant coils in a strongly coupled regime, we experimentally demonstrate efficient non-radiative power transfer over distances of up to eight times the radius of the coils. We demonstrate the ability to transfer 60W with approximately 40% efficiency over distances in excess of two meters. We present a quantitative model describing the power transfer which matches the experimental results to within 5%. We discuss practical applicability and suggest directions for further studies.
The Science article requires a subscription for full text. However, the free pre-print is available (this is the theory paper cited above): Efficient wireless non-radiative mid-range energy transfer We investigate whether, and to what extent, the physical phenomenon of long-lifetime resonant electromagnetic states with localized slowly-evanescent field patterns can be used to transfer energy efficiently over non-negligible distances, even in the presence of extraneous environmental objects. Via detailed theoretical and numerical analyses of typical real-world model-situations and realistic material parameters, we establish that such a non-radiative scheme could indeed be practical for medium-range wireless energy transfer.
His talk at the 2006 AIP Physics Forum was entitled, "Wireless Non-Radiative Energy Transfer", so presumably the method is not the one that Decius remembers from school lessons. The figures are freely available as a PDF, including a photo: "Figure 3: 60W light-bulb being lit from 2m away." There is a WIPO patent on the method: 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.
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