Revolutionize Charging with RCA Airnergy: Harness WiFi Energy Harvesting!

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Discussion Overview

The discussion revolves around the RCA Airnergy device, which claims to harvest energy from WiFi signals to charge devices. Participants explore the feasibility of this technology, its potential applications, and the efficiency of energy harvesting from WiFi, focusing on theoretical and practical implications.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant expresses skepticism about the practicality of the Airnergy, questioning the time it would take to accumulate a meaningful charge from typical WiFi routers.
  • Another participant argues that the efficiency of the router's power transmission and the loss of power over distance significantly limit the potential energy that could be harvested.
  • Some participants acknowledge that while the concept seems dubious, reputable companies are exploring similar technologies, suggesting that it might improve battery life rather than fully charge devices.
  • Concerns are raised about the actual power levels that could be harvested, with estimates suggesting only microWatts of energy, which may not be sufficient for practical use.
  • There is a suggestion that energy harvesting from movement or thermal sources might be more viable than from WiFi signals.
  • One participant proposes that devices requiring minimal power in standby mode could benefit from this technology, especially when combined with a battery.
  • Another participant questions the overall worth of the technology, citing the significant power loss expected in real-world scenarios and comparing it to the energy needs of typical devices.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus, with multiple competing views on the feasibility and practicality of energy harvesting from WiFi signals. Some express skepticism about the claims, while others suggest potential applications under specific conditions.

Contextual Notes

Participants highlight limitations related to the assumptions about power transmission efficiency, the distance between transmitters and receivers, and the specific energy requirements of devices. The discussion remains open-ended regarding the practical applications of the technology.

MATLABdude
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A little gizmo with one heckuva claim was demonstrated at the Consumer Electronics Show (CES) recently. The Airnergy by RCA claims to be able to scavenge enough energy from WiFi (and presumably the 2.4GHz band) to juice up its own internal battery and allow a user to charge up devices on the go:
http://m.gizmodo.com/site?sid=gizmodoip&pid=JuicerHub&targetUrl=http%3A%2F%2Fgizmodo.com%2F5444850%2Frca-airnergy-charges-gadgets-with-nothing-but-wifi-signals%3Fop%3Dpost%26refId%3D5444850

Perhaps this should be in the Product Claims subforum, but I can't imagine how long it'd take to build up even a few dozen mAh of charge with 40 mW routers. Perhaps as an emergency, always available source, but as something used on a regular basis? I don't know if I buy it.
 
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Sounds like total nonsense.
Bear in mind
1. the efficiency of the Router transmitter, in terms of total power supplied vs actual transmitted RF power and
2. The loss of power over the RF link (assuming you're not in an ellipsoidal reflecting box with Tx and Rx at the foci)

How much significant energy could the system POSSIBLY yield?
 
I agree that it sound fishy, But there are a number of companies working on this and some of them have a pretty good reputation when it comes to innovations I might be wrong but I think I've read somewhere that Nokia are working on something similar and have already demonstrated a prototype It wouldn't give you enough energy to actually charge the battery if it it was empty, but the claim is that this technique might improve battery life somewhat.
 
Despite their possibly good reputations you can't argue with the figures, can you? You're talking tens or hundreds of microWatts, tops, when you're close to the transmitter. Let's face it - they use a receiver with an amplifier, to produce enough power to detect and decode the actual WiFi signal. Why would they bother, if there was enough received power to operate a "crystal set'?
A much better potential source of energy would be movement (like kinetic watches) or thermal.
 
But there are quite a few devices that only require a say 100 uW in standby-mode, and for those it might be a useful technique for extending battery life; at least when combined with a battery.

Also, the "harvester" would presumably be a separate circuit, it would obviously not make sense to operate it while using an amplifier at the same time so the rest of the RF circuitry would have to be in standby mode when using the harvester (and maybe only respond to a very simple and strong "wakeup" signal).
 
This feels wrong to me. The maximum permitted radiated power from a WiFi device is, according to Wikkers, 100mW and this would be radiated omnidirectionally, more or less. It would be very lucky to get as little as 30dB of loss between transmitter and receiver - without my silly scenario or a dedicated, directional antenna at each end. This would make even a modest 100uW much too much to hope for.

When you think that 100uW is the sort of power that a tiny battery would give you for months, in any case, I really question it as being worthwhile, at all. It is insignificant compared with the load which the 'main' equipment would be needing - even for a few minutes at a time (we're looking at very esoteric applications here, at best and not a domestic scenario). A device which would need to run for a long time without attention would be, necessarily, a long way from a base station and be receiving the very minimum of signal strength.
There are occasional threads on fora about 'wireless power transmission' and this seems to be another of the same. We could just as well discuss the possibility of having a Radio receiver which we could use once in a blue moon which is operated by off-air power. Anyone who has made a crystal set will know that you need a pretty huge aerial installation to get energy out of the Aether. That tends to be true whatever frequency you are working at.