Is Nokia's Cell Phone Recharging via Radio Waves Really Possible?

Click For Summary

Discussion Overview

The discussion revolves around the feasibility of Nokia's technology that purportedly allows cell phones to recharge using ambient radio waves. Participants explore the theoretical implications, practical applications, and potential limitations of this concept, touching on aspects of energy harvesting, efficiency, and the technology's viability in various environments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants express skepticism about the practicality of harvesting sufficient energy from ambient radio waves, questioning whether the energy output would be enough to charge a phone effectively.
  • Others suggest that if Nokia's goal of 50 milliwatts is achieved, it could be beneficial, especially if combined with other sources of radio waves like TV and Wi-Fi signals.
  • Concerns are raised about the density of radio energy in different locations, with some participants wondering if this technology would primarily benefit urban areas.
  • Participants discuss the potential need for calculations regarding the density of radio energy and the efficiency of energy harvesting methods, including the orientation and surface area of the phone.
  • There is a mention of the legality of harvesting energy from radio waves, with some participants speculating about the implications of individuals setting up devices to capture this energy.
  • One participant contrasts the concept with induction charging technologies, expressing a desire for more detailed information before fully endorsing the idea.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the feasibility or practicality of the technology. There are multiple competing views regarding the efficiency of energy harvesting from radio waves and its potential applications.

Contextual Notes

Participants highlight limitations related to assumptions about energy density, the efficiency of energy conversion, and the potential legal implications of harvesting radio energy.

OAQfirst
Messages
23
Reaction score
3
I'm not knowledgeable about these things, with all the free energy nonsense I frequently see. So what do you think?

http://tech.yahoo.com/blogs/null/143945
Nokia, however, has taken another baby step in that direction with the invention of a cell phone that recharges itself using a unique system: It harvest ambient radio waves from the air, and turns that energy into usable power. Enough, at least, to keep a cell phone from running out of juice.
Does this sound right? If so, it looks like exciting news. Even for stand-by charging, that's still a good thing.
 
Last edited by a moderator:
Computer science news on Phys.org
You have to assume Nokia have done their sums.
But assuming the signal is a couple of milliwatts and you leave it on continually.
My phone battery is 700mAh x 3.6V so stores around 2.5Wh, charging with 1mW would take 3months! It's difficult to believe it's even enough to overcome the leakage in the charging circuit.
 
It reports their goal is 50 milliwatts. Would that be substantial enough?
 
My phone lasts a week on standby with a 2500mWh battery so around 15-20mW - if they can pull 50mW out of the air that would certainly help.
I suppose if they didn't just use the phone antenna they could also use the power form lots of other transmitter sources, TV/radio/wifi etc.
 
Hmm. Well, here's to hoping!

Thanks.
 
Would this phone technology be useful only to those in major cities?
 
Presumably. I wonder if anyone has actually calculated how dense the radio energy is in various places.

[edit] calculation deleted. I guess you'd want to do a calculation based on surface area...
 
Last edited:
...and over what range of frequencies?
 
russ_watters said:
Presumably. I wonder if anyone has actually calculated how dense the radio energy is in various places.

[edit] calculation deleted. I guess you'd want to do a calculation based on surface area...

I immagine you would want to make your windings as large as possible to contain the maximum amount of magnetic flux. Probabilly the entire surface area of the phone. Also, if the phone wasn't sitting in the correct orientation with the source, you wouldn't get anything.
 
  • #10
The surface area of a 1"x2"x4" phone is 8 square inches. At 50mw, that's 900 mw/sq ft. The side surface area of my 19x14x8' living room is 528 square feet, which would mean if I wrapped it with antennas, could generate 475 w. My house is 20'x40'x20', or 2400 square feet side surface area. That's 2.1 kW, which (with storage), would be more than enough to supply all my energy needs.

I find that hard to swallow.
 
Last edited:
  • #11
OAQfirst said:
It reports their goal is 50 milliwatts. Would that be substantial enough?

Over what time frame?

When would this be most useful? I'd think if you were stranded out in the wilderness without a charger is when you'd need something like this...one would hope the charge would happen fast enough to call for help before you die of dehydration or exposure to the elements. Otherwise, it's nothing more than a gimmick.
 
  • #12
miliwatts is power, Moonbear - it's got a timeframe in it (seconds).
 
  • #13
Isnt it illegal to 'harvest' energy from radio waves? I could imagine those who live near the transmitters putting up huge coils on their houses to sap up the free kilowatts.
 
  • #14
russ_watters said:
miliwatts is power, Moonbear - it's got a timeframe in it (seconds).

D'oh. Sorry, I made the classic mistake of mixing up power and energy. Thanks for the correction.
 
  • #15
Blenton said:
Isnt it illegal to 'harvest' energy from radio waves? I could imagine those who live near the transmitters putting up huge coils on their houses to sap up the free kilowatts.

What transmitter?
 
  • #16
Radio station transmitters.
 
  • #17
Blenton said:
Radio station transmitters.

I would think that's somtehing you could do right now. I was thinking he meant that Nokia was planning on building transmitters specifically for recharging cell phones.
 
  • #18
No I believe they meant radio waves currently in the air.
 
  • #19
Before I read the Yahoo! article, I assumed induction, like the contact-free charger for my Braun toothbrush, or the ones used to recharge cardiac pacemakers and ICDs (implanted defibrillators). It doesn't look like that's what they meant.

My immediate image was of holding a four-foot fluorescent tube under an HT power transmission line and seeing it glow dimly. Kinda neat, but not a lot of oomph for being so close to the EM source (albeit 60Hz, not RF). I aint' doin' the math for that, so I'd like to see a white paper or something before I throw away my chargers.

Neat topic
 

Similar threads

Cell Phone EM Waves - Health Risks & Physics Explained
  • · Replies 10 ·
Replies
10
Views
3K
How can Nokia's radio wave-powered cell phone generate enough energy to operate?
  • · Replies 8 ·
Replies
8
Views
3K