Slashdot Mirror
Is RCA's Airnergy Snake Oil?
Ben Newman writes "Of all the tech that's come out of CES this week, nothing has gotten the blogosphere more excited then the RCA Airnergy. A lot of people love the thought of an ever-recharging cell phone, and the Airnergy promises to constantly charge its internal battery through 2.4GHz wireless signals. Neat idea, but as some commenters have pointed out the energy just isn't there to make this work — BOTECs for a full charge range from 100 days to 32 years. Plus, don't let the RCA brand fool you into thinking this must be from a legitimate company: RCA hasn't existed as anything more then a licensed brand name for a couple of decades. So what do Slashdotters think — real deal or 21st century hokum?"
Nasa HAS tried this.
http://en.wikipedia.org/wiki/Electrodynamic_tether
You can generate electricity as you move around the earth. Being in orbit, you are going fast enough to make worthwhile magnetic flux, and you are free of air resistance that would keep you from deploying the tether if you were lower in the atmosphere.
Much earlier than the mythbusters a german tv-show for kids, the "Sendung mit der Maus" ("program with the mouse") made the point: they held up a neon tube next to a state radio-transmitter and it began to glow. And they explained to the kids, that it will work next to such a high energy radio transmitter, but it is also robbery according to german law. So don't try, kids, unless you don't mind being a thief.
How can you steal that what is freely given? Laws are weird.
Multiply it by the hundreds to thousands of cellphones within one cell ... can you imagine how much power the cell tower much emit in order to charge all those phones?
FWIW: the article says that the charger makes electricity from "ambient WiFi signals" -- not from the cell tower. Allegedly, at the trade show, "they were able to charge a BlackBerry from 30% to full in about 90 minutes."
That's amazing, because it takes that long to charge my POS cell from the wall with a ... hmmm... ya know, something just doesn't seem right here...
If you aren't suspicious of your government's actions, you aren't doing your job as a responsible citizen.
You just failed physics 101. Frequency has absolutely no impact on energy in a signal.
Indeed, That's Why the the GHz Barrier was a myth, in fact we should have Thz machines if it weren't for the man keeping them down.
*cough*E = h*(c/lambda)*cough*
I tried it with a 500mW power source on 460MHz using a pair of resonant quarter-wave aerials. At about one metre separation, it was receiving around -6dBm, or about 250uW. So that's ten times the power, ten times closer, on a lower frequency with better propagation. Ten metres away and 50mW would give -26dBm which my meter won't measure, but is one hundredth the power - 2.5uW. Good luck charging a battery with that.
Gordon MM0YEQ
Meh, according to the German broadcasting agency I'm already stealing radio waves by owning a computer.
I'm not kidding.
You use the "nu" when dealing with particles. For waves it is f. In electronics it is practically always f.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
They didn't even need to do that for this demo. They "pre-charged" it using WiFi, with no indication of how long it took to charge. They probably had to have the prototype built back in June or July and set it right next to a dedicated access point dialed up to "11" since then to get enough charge to top a Blackberry from 30% to 100%.
If they're really lucky, they'll have the SAME device recharged for CES next year and it can charge a Blackberry from 0% to 100%. They'll have to have 4-5 more access points dedicated to charging it, of course, for the entire year.
Kind of expensive for a device that can pull maybe $1 worth of electricity each YEAR. It's got an 40-year ROI, and it'll probably last about 3.
"This post contains words, known to the State of California to cause thought. Wash brain thoroughly after reading."