In reply to Harry Veeder's message of Sun, 24 Mar 2013 22:21:19 -0400: Hi, [snip] >Nokia developing phone that recharges itself without mains electricity > >Prototype harvests radiowaves from TV, radio and other mobiles > > >http://www.guardian.co.uk/environment/2009/jun/10/nokia-mobile-phone > >quote <<...Nokia claims it is able to scavenge relatively large >amounts of power around a thousand times as much from signals >coming from miles away. Individually the energy available in each of >these signals is miniscule. But by harvesting radiowaves across a wide >range of frequencies it all adds up, said Rouvala. > >Such wireless transfer of energy was first demonstrated by Nikola >Tesla in 1893, who was so taken with the idea he attempted to build an >intercontinental transmission tower to send power wirelessly across >the Atlantic. Nokia's device is somewhat less ambitious and is made >possible thanks to a wide-band antenna and two very simple circuits. >The antenna and the receiver circuit are designed to pick up a wide >range of frequencies from 500 megahertz to 10 gigahertz and >convert the electromagnetic waves into an electrical current, while >the second circuit is designed to feed this current to the battery to >recharge it.>> end quote > >Harry
If they extended the range to below 50Hz, they could pick up the stray field from the grid, which is much larger than the RF transmissions they are harvesting now. Since most of this would be harvested indoors, it would automatically be charged to the users account anyway. (Although it would only be worth a fraction of a cent.) Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
