Comments on: Radio waves: Future way to help keep e-book readers charged up? http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/ News & views on e-books, libraries, publishing and related topics Sat, 20 Mar 2010 15:09:48 -0500 http://wordpress.org/?v=2.9.2 hourly 1 By: Joseph Gray http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/comment-page-1/#comment-1076414 Joseph Gray Wed, 10 Jun 2009 17:21:55 +0000 http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/#comment-1076414 This idea has been around for almost as long as radio has. I built a circuit that did this when I was a kid. As the article states, the amount of energy that can be extracted this way is very tiny. The 3-5 mW that Nokia is currently extracting is actually pretty good. I think they will have a tough time getting 50mW. Even with 50mW, this isn't nearly enough to charge a cell phone. It will only be good for very slowly trickle charging a mostly charged device. Rechargable batteries take a significant amount of current when they are even partially discharged. To put this in perspective, the amount of power available from a computer's USB port is 2.5W, which is 50 times the 50mW Nokia is aiming for. And we're not even considering losses due to circuit/charging efficiency. BTW, they are talking about using "ambient" radio signals, not some high power RF that is transmitted specifically for this purpose. This idea has been around for almost as long as radio has. I built a circuit that did this when I was a kid.

As the article states, the amount of energy that can be extracted this way is very tiny. The 3-5 mW that Nokia is currently extracting is actually pretty good. I think they will have a tough time getting 50mW.

Even with 50mW, this isn’t nearly enough to charge a cell phone. It will only be good for very slowly trickle charging a mostly charged device. Rechargable batteries take a significant amount of current when they are even partially discharged.

To put this in perspective, the amount of power available from a computer’s USB port is 2.5W, which is 50 times the 50mW Nokia is aiming for. And we’re not even considering losses due to circuit/charging efficiency.

BTW, they are talking about using “ambient” radio signals, not some high power RF that is transmitted specifically for this purpose.

]]> By: Steve Jordan http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/comment-page-1/#comment-1076381 Steve Jordan Wed, 10 Jun 2009 16:13:49 +0000 http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/#comment-1076381 Yes: Depending on the radio frequency used, there could be biologic issues... but we get bombarded with radio waves all the time, including low-power microwaves, with no ill-effects. The receiver will also be an important part of how flexible they are on which frequencies they can use to transmit power without creating biological hazards at the same time. We'll just have to see what Nokia comes up with. Yes: Depending on the radio frequency used, there could be biologic issues… but we get bombarded with radio waves all the time, including low-power microwaves, with no ill-effects. The receiver will also be an important part of how flexible they are on which frequencies they can use to transmit power without creating biological hazards at the same time. We’ll just have to see what Nokia comes up with.

]]> By: David Rothman http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/comment-page-1/#comment-1076325 David Rothman Wed, 10 Jun 2009 13:17:28 +0000 http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/#comment-1076325 Absolutely, Steve. Of course one little detail makes me a bit nervous. If the radio waves are strong enough to power gadgets, what does this mean in terms of health risks from the same energy? Not sure. I'd love to hear people's thoughts on this issue--the Topic Police in this case are on vacation (not that they're that powerful anyway around here). Any interesting links people can dig up with authoritative information? David Absolutely, Steve. Of course one little detail makes me a bit nervous. If the radio waves are strong enough to power gadgets, what does this mean in terms of health risks from the same energy? Not sure. I’d love to hear people’s thoughts on this issue–the Topic Police in this case are on vacation (not that they’re that powerful anyway around here). Any interesting links people can dig up with authoritative information?

David

]]> By: Steve Jordan http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/comment-page-1/#comment-1076310 Steve Jordan Wed, 10 Jun 2009 12:46:28 +0000 http://www.teleread.org/2009/06/10/radio-waves-way-to-help-keep-e-book-readers-charged-up/#comment-1076310 I don't see this can't work with almost any low-power electronic gadget. It's something to look forward to. I don’t see this can’t work with almost any low-power electronic gadget. It’s something to look forward to.

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