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Radio Energy Harvested With Inkjet-Printed Antenna

Posted by samzenpus on from the catching-the-waves dept.

judgecorp writes "Everlasting green energy for RF tags and other low-power devices could be possible as scientists have harvested energy from ambient radio waves using cheap antennas printed by an ordinary inkjet. The scientists, from Georgia Tech, started at 100MHz but have now produced systems which scavenge power at up to 60GHz, allowing them to draw power from most of today's major radio technologies."

13 of 164 comments (clear)

  1. So they're using background radiation only? by Anonymous Coward · · Score: 3, Insightful

    Because it seems like if you want to power these things, they need to use power from a radio source. Which doesn't make them green at all.

    1. Re:So they're using background radiation only? by icebike · · Score: 5, Informative

      Because it seems like if you want to power these things, they need to use power from a radio source. Which doesn't make them green at all.

      The radio source is there all the time anyway, It is there for other uses.

      But as should be obvious, the vast majority of radio waves are never used, being disparate over vast distances or absorbed by the earth itself. Utilizing this "wasted" energy costs nothing, because we are already emitting that energy, and utilizing it costs no more. At the emitter you can't measure if a radio wave hits one antenna or a million antennas. Its no different to you as the sender of that wave.

      So by using freely available wasted energy these devices obviate the need for ANOTHER power source and are therefor green.

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    2. Re:So they're using background radiation only? by fuzzyfuzzyfungus · · Score: 5, Interesting

      Because it seems like if you want to power these things, they need to use power from a radio source. Which doesn't make them green at all.

      They do, indeed, consume some energy from the RF broadcast(in principle, if you really chaffed the place with them, the reduction in SNR might actually be noticeable by devices trying to communicate...) However, there are two other considerations:

      1. Particularly in classic broadcasting(less your fancy 802.11-draft-whatever-with-beamforming-and-a-line-of-sight-yadda-yadda smart antenna nonsense) a substantial amount of broadcast power just floats away into the aether, never to be snagged by any receiver. So long as you are(by making receivers super cheap) just burning through some of this formerly wasted power, the energy counts as "free". Not until your piggybacking requires the towers to start cranking it up is their a cost.

      2. If the deployment of some distributed-sensor net widgetry is an inevitability(there are legimitate grounds for question at this point; but we generally don't take advantage of them) it has to be powered somehow. The major contenders are A. Lithium primary cells: unless somebody plans on cleaning the whole thing up a decade from now, the delightsome battery goo is going straight into the environment. B. Photovoltaics(in suitably sunlit locations that are OK with sporadic power): the energy generation itself is clean, the manufacturing and some of the components are rather less so. C. Piezoelectrics: not all of the suitable candidates contain lead; but a lot of the common ones really ought to be collected after use.

      In our brutally entropic universe, nothing is truly "green"; but it is quite possible that RF harvesting will prove to be green-er and/or more convenient in some applications.

  2. radio harvested with piece of rock (galena) by YesIAmAScript · · Score: 5, Informative

    It's called a crystal radio.

    A diode does it too.

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    http://lkml.org/lkml/2005/8/20/95
    1. Re:radio harvested with piece of rock (galena) by fuzzyfuzzyfungus · · Score: 4, Informative

      It's called a crystal radio.

      A diode does it too.

      The "offtopic" is hardly fair, RF-energy harvesting(conveniently combining the signal and the power) found its first major application in early AM radio setups. TFA, though, focuses on advances in antenna design and fabrication that allow much more compact, and far broader-spectrum energy harvesting. The AM antennas of yore, particularly in designs without any amplifiers available, were often not exactly monuments to compactness...

  3. Re:dumb question by houstonbofh · · Score: 4, Informative

    Yep. TANSTAAFL

  4. Re:dumb question by icebike · · Score: 3, Informative

    Maybe a dumb question, but do RF sinks like this act like 'black holes' for radio waves, affecting the reception quality within a kind-of 'event horizon' vicinity (maybe even requiring more power at the transmitter) ?

    I don't think you can measure the effect at the transmitter of generating a wave that was otherwise destined to be absorbed by the surroundings or dissipated into space vs being detected on an antenna.

    Perhaps a log floating on a pond into which you throw a rock blocks the ripple and creates a lee, and perhaps a lillypad in that lee bobs less, bit it makes no difference to the stone you throw unless your primary aim was to ripple that particular lillypad.

    I suppose you could totally mask the intended receiver (TV aerial) of that TV signal by wrapping it in these paper antennas.
    But the energy was already expended sending the wave. The transmitter won't need more power if that signal gets absorbed by the buildings or by the paper antenna. The antenna can only capture the energy already impinging upon it from the signal. It can't pull any more from the transmitter.

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    Sig Battery depleted. Reverting to safe mode.
  5. Re:Big numbers by Fordiman · · Score: 3, Interesting

    I wonder what the nominal ambient flux actually is (i.e., W/m^3), and how much of it they're actually capturing.

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    110100 1101000 1101000 1100110 0 1101111 1101000 1100011 1
  6. FCC says? by HTH+NE1 · · Score: 4, Interesting

    Which reduces the quality of the radio signal for anyone downwave from the power harvesting site. It effectively steals power from the transmitter intended to provide service to those more distant than you from the transmitter.

    Permissible is interception for purpose of reception of the signal, such as a crystal radio, at a small scale. Not permissible is powering your lights, robots, or anything else that does not simply turn the signal back into its intended form.

    It may be permissible to leech power from a WiFi signal in order to power a device that will use the data in the stream if you could be sure you're stealing power from signals intended for you and no one else.

    But AFAIK the rules are to protect man-made signals, unless the scientific community have petitioned to protect their ability to study background radiation by preventing the same harvesting of power from natural radio sources, else they'll have to do their studies elsewhere.

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    1. Re:FCC says? by labnet · · Score: 4, Insightful

      Which reduces the quality of the radio signal for anyone downwave from the power harvesting site. It effectively steals power from the transmitter intended to provide service to those more distant than you from the transmitter.

      Permissible is interception for purpose of reception of the signal, such as a crystal radio, at a small scale. Not permissible is powering your lights, robots, or anything else that does not simply turn the signal back into its intended form.

      It may be permissible to leech power from a WiFi signal in order to power a device that will use the data in the stream if you could be sure you're stealing power from signals intended for you and no one else.

      But AFAIK the rules are to protect man-made signals, unless the scientific community have petitioned to protect their ability to study background radiation by preventing the same harvesting of power from natural radio sources, else they'll have to do their studies elsewhere.

      A little bit of knowledge is a dangerous thing!

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      46137
  7. Re:IANARS, but... by Tacvek · · Score: 5, Informative

    It will degrade the signal of downstream recipients. So does absolutely every radio receiver, with no exceptions.
    However, please consider that the only downstream recipient may well be the earth or space, considering that the path between a transmitter and receiver often does not pass particularly close to another receiver. How much one of these would impact the downstream signal quality anyway depends on just how much power this is extracting, and just how weak the signal would have been at the downstream receiver without this being present.

    Also keep in mind that radio waves can be rather fickle. Placing these devices in certain locations may actually increase the received signal strength downstream, perhaps by absorbing an interference source, or by attenuating a secondary path of the signal which would have interfered with the primary signal.

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  8. Re:Big numbers by Omniscient+Lurker · · Score: 3, Informative

    Joke all you want. But a group in one of my engineering classes did this and we were received better than the group that did: .00something watts.

    I guess marketing is easy.

  9. Re:IANARS, but... by rubycodez · · Score: 4, Informative

    more broadly, so does every conductor in an RF field. We'd better outlaw file cabinets, metal kitchen utensils, pocket change and reinforced concrete buildings.