Nokia Developed Wireless Power-Harvesting Phones 246
Al writes "An engineer from Nokia's UK research labs says that the company is developing technology that can harvest ambient electromagnetic radiation to keep a cellphone going. The researcher says that his group is working towards a prototype that could harvest up to 50 milliwatts of power — enough to slowly recharge a phone that is switched off. He says current prototypes can harvest 3 to 5 milliwatts. It will require a wideband receiver capable of capturing signals from between 500 megahertz and 10 gigahertz — a range that encompasses many different radio communication signals. Other researchers have developed devices that can harvest more modest power from select frequencies. A team from Intel previously developed a compact sensor capable of drawing 6 microwatts from a 1.0-megawatt TV antenna 4.1 kilometers away."
Why not solar? (Score:3, Interesting)
Question. Won't this weaken the RF signal? (Score:3, Interesting)
Harvest motion energy as well (Score:5, Interesting)
Shouldn't be too hard to harvest energy from changes of momentum and orientation, similar to how many mechanical watches have for years been able to wind themselves.
College experiments (Score:3, Interesting)
Re:didn't Tesla do this decades ago? (Score:3, Interesting)
And playing Star Wars lightsaber battles using florescent light tubes at night under high power lines.
Henrich Hertz (Score:5, Interesting)
Another great example as to how Tesla has shaped our future. Truly ahead of his time by leaps and bounds.
I know Tesla is a posterboy for the Slashdot community, but I think you mean http://en.wikipedia.org/wiki/Heinrich_Hertz [wikipedia.org]. Hertz was responsible for the discovery that you could generate and detect radio waves.
That lead to the use of radio for communications, which is why such a modern device as the article describes. Tesla envisioned pumping energy into the air via dedicated stations. I don't think he envisioned a situation where we would be pumping so much energy into the air for communications, that there would be usable power as a byproduct.
I find it frightening, not "cool", that such a device is possible, given that my body relies on faint electrical signals.
Re:Crystal radio (Score:4, Interesting)
As a very young geek I spent many a night tucked in bed listening to my crystal (actually geranium) radio. But I had a couple of metres of hookup wire for an antenna. This article talks about short wavelength stuff, but I still think you would need a lot of metal to collect a significant amount of power. MY cellphone charger supplies (I think) 300mA.
Re:Crystal radio (Score:3, Interesting)
Not really. Cellphones, along with cars, buildings, trees, people, and nearly everything else will already weaken the signal. That's why devices can easily transmit 10 billion* times more power than would be needed by the receiver in a lossless environment. We might as well grab some of that power back out of the air and put it to good use, instead of just letting it turn to heat.
* 10 billion == 100 dB, which is an entirely reasonable attenuation from transmitter to receiver, but the actual multiplier varies. Most devices will adjust their output power based on the strength of the signals they're receiving so as not to waste electricity.
Re:Crystal radio (Score:4, Interesting)
One of their operational transmitters had a gauge showing two kilowatts of reflected power from the antenna. We asked, but the staff wouldn't let us take it home, even though they weren't using it for anything.
Why not atomic? (Score:3, Interesting)
Why not atomic?
What made me think of this was the digital watch I had back in the late seventies that used radioactive tritium for a backlight. It was bright enough on a dark night to use as a flashlight. The only downside was that there was no way to shut it off, a disadvantage when going out to a movie. (Oh, and my left arm fell off. Not really.)
The significant advance since the times of Tesla is that devices take much less power to operate, which is, I think, the real reason broadcast power has become interesting again.
During recent years, there's been significant advances in atomic batteries. So, given that, why not atomic? If a device is typically replaced every three years (or one year if from Apple), I wonder if a tritium betavoltaic (for instance) of sufficient capacity could be made small enough to reside in the device, either powering it directly or charging a conventional battery during periods of unuse.
I'm thinking, watches, almost certainly. Solid state personal music players, possibly. Phones... maybe?
Re:Harvest motion energy as well (Score:3, Interesting)
Shouldn't be too hard to harvest energy from changes of momentum and orientation, similar to how many mechanical watches have for years been able to wind themselves.
Like these guys. [cnet.com]
Re:Crystal radio (Score:5, Interesting)
Re:didn't Tesla do this decades ago? (Score:2, Interesting)
Re:didn't Tesla do this decades ago? (Score:3, Interesting)
The power doesn't actually flow IN the wires. It flows in the fields AROUND the wires. It falls off pretty fast. But there's a LOT of power in a high-line so there's a non-trivial amount at ground level outside the right-of-way.
Back in the '60s at EE school I heard a story (from the prof). Seems a farmer who had the local power company eminent-domain a right-of-way through his land to put in a high-line, but still wanted tens of thousands to run a service drop to his farm. This guy got ticked. So he strung his own line under the high-line, thus coupling to it (both inductively and capacitively) and used ordinary utility transformers to convert the tapped power to a voltage suitable to run his milking barn.
Power company noticed the drain and tried to bill him. He told 'em to get stuffed. So they sued him. Judge told 'em if they couldn't keep their power in their lines they had no claim on it if somebody picked up and used what had leaked outside their right-of-way. Nyah-nyah. Power company said that doing this was dangerous. Farmer said he'd keep doing it regardless of their claims.
Then the power company did a little switching of the line. This threw some big transients down it. The farmer's equipment arced over and burned down his barn.
At least that's how the story went. It was a lead-in to a lesson on the problems of switching transients in power transmission lines. So I have no idea how much of it is apocryphal, whether there are precedents since, or how a judge might rule in a current case.
But if I were to try it I'd make sure the lines were outside their right-of-way (so I could argue that if they didn't want to give away the power they should have bought enough of a right-of-way to contain it and put up shielding wire runs inside the boundary to keep it in - cheapskates exposing people to their EM fields etc.) and be sure to include surge arresters at the load end my wiring.