As I recall, 10.000MHz is used in the USA as a frequency standard, time of day and time interval and some meteorological information. Perhaps the MIT demonstration wasn't done at preciously that frequency. The demo would be brief and might get repeated a couples of times per semester. I'm guessing that's not something the FCC would be concerned about. _____________________________________________________________________________________
Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer From: "o. laney" <[email protected]> To: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: 05/18/2010 11:34 AM Subject: Re: [PSES] Wireless Power Transmission ________________________________ Wireless power transmission in the HF region is definitely not a 'green' technology, with efficiencies hovering around 60% at best for any useable separation distance. Of course, if you make the distance zero then efficiency can be more like 96% -- it's called a transformer. Better yet, use wires and get 99+% for a well designed interconnect, at a tiny fraction of the price of wireless. Maybe I should patent that... Given the low efficiency of the MIT scheme and for other reasons that resonate (so to speak) at multiple levels, I refer to wireless power as a 'brown' technology. Also note that the MIT psuedoinvention has a scaling issue. Want two meters distance at about the same efficiency? Then use two meter coils! Ten meters? Well, you get the idea. I suppose that you could power everything in a house by putting a pair of coils on the outside walls, assuming you are willing to live in the EM field of a giant helmholtz coil and pay electric bills that are twice normal. The comment about 10MHz being a protected frequency is absolutely correct. I was appalled that the MIT folks were so clueless. There has been some serious work at microwave frequencies, where it is possible to at least focus the energy. One company http://www.powerbeaminc.com/industry.php <http://www.powerbeaminc.com/industry.php> uses infrared laser diodes at 214 THz. As yet unexplored is the possibility of using giant fans to turn your house into a wind tunnel so miniature wind turbines can power your appliances, all in the name of avoiding efficient, cheap, and simple power cords. Orin Laney On Tue, 18 May 2010 06:25:31 -0700 "Price, Edward" <[email protected] <mailto:[email protected]> > writes: 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] <mailto:[email protected]> > All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc <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/ <http://www.ieee-pses.org/> Instructions: http://listserv.ieee.org/request/user-guide.html <http://listserv.ieee.org/request/user-guide.html> List rules: http://www.ieee-pses.org/listrules.html <http://www.ieee-pses.org/listrules.html> For help, send mail to the list administrators: Scott Douglas <[email protected] <mailto:[email protected]> > Mike Cantwell <[email protected] <mailto:[email protected]> > For policy questions, send mail to: Jim Bacher <[email protected] <mailto:[email protected]> > David Heald <[email protected] <mailto:[email protected]> > ________________________________________________________________________ This email has been scanned for SPAM content and Viruses by the MessageLabs Email Security System. ________________________________________________________________________ - 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] <mailto:[email protected]> > All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc <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/ <http://www.ieee-pses.org/> Instructions: http://listserv.ieee.org/request/user-guide.html <http://listserv.ieee.org/request/user-guide.html> List rules: http://www.ieee-pses.org/listrules.html <http://www.ieee-pses.org/listrules.html> For help, send mail to the list administrators: Scott Douglas <[email protected] <mailto:[email protected]> > Mike Cantwell <[email protected] <mailto:[email protected]> > For policy questions, send mail to: Jim Bacher <[email protected] <mailto:[email protected]> > David Heald <[email protected] <mailto:[email protected]> >
