I recently read a follow-up on wireless transmission of energy. Back maybe as long as last year, there was a burst of publicity about a prof at MIT(?) who had created a demonstrator of energy transfer. The demo showed about a 1 square meter, several turn, flat coil transmit and a similar receive antenna; the separation distance was also about a meter. The receive and transmit antennas had parallel tuning capacitors, and the receive antenna drove a 40 Watt incandescent lamp (not clear if the lamp was in series or parallel with the capacitor).
OK, the point is that I was surprised to see transmission of 40 Watts over a meter. At the time, the tech details were slim, but the follow-up points out that the operational frequency of this demo was 10 MHz! And the efficiency was somewhere around 10%. Of course, the prof wasn’t claiming anything about efficiency, he just wanted to show the transfer demonstration. My immediate reaction is that he was pumping out maybe a half kW at 10 MHz! Didn’t anybody notice that the room felt strangely warm, and that some digital cameras did strange things? My second reaction was that 10 MHz is an internationally protected frequency (no emissions allowed at all, to protect time-standard signals). He might at least move on over to 13.56 MHz. In any case, all these schemes about wireless power transmission seem to crash on the shores of acceptable human exposure. Remember those wild schemes from the 60’s, where huge orbital solar arrays would convert sunlight to microwave, and then beam it back to Earth? Maybe that’s where the concept of aluminum foil hats originated! Ed Price [email protected] <blocked::mailto:[email protected]> WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
