If you transmit the rf energy through sub-space that will solve the exposure problem.
Yea, my electric tooth brush has an inductively coupled battery charger. Very nice design because there are no contacts to corrode and go bad. You would think that efficiency would be improved if you could use a frequency and antenna system that would transfer the energy in a focused narrow beam, such as microwave or laser. That would help the exposure problem as well, unless you stood in the wrong place. Ouch! The Other Brian ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Dan Roman Sent: Tuesday, May 18, 2010 9:50 AM To: Price, Edward; [email protected] Subject: RE: Wireless Power Transmission Ed, I saw the same article. I agree, it wouldn’t meet the FCC exposure limits for transmitters/antennas either. What about conducted and radiated limits!?! BPL is having trouble, now power through air? I can see inductively charging batteries at a close distance and I actually have a gadget or two that does that. The ability to put coils in the walls of a house and be able to put a wireless lamp anywhere in the room you like, while a neat idea, seems just too impractical to bother considering. Dan From: Price, Edward [mailto:[email protected]] Sent: Tuesday, May 18, 2010 9:26 AM To: [email protected] Subject: [PSES] Wireless Power Transmission 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. 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