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  • EEVblog #55 – RCA Airnergy WiFi Hotspot Energy Harvesting Marketing BS

    Posted on January 17th, 2010 EEVblog 41 comments

    Dave can smell marketing bullshit a mile away, so checks out the new RCA WiFi Energy Harvesting “Airnergy” device with some back of the envelope calculations. Marketing BS? or can it actually work?

    The RCA video is HERE
    and another interview HERE

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    • http://truthspew.wordpress.com Tony P

      Great debunk Dave! Yeah, when I heard about this I wondered how they’d pull it off. I note it appears to have a USB plug on it. Plugging it into a computer would charge it at a reasonable clip, at least a couple of watts on the USB port.

      And btw, RCA is mostly made by SGS Thompson, a French firm.

      • http://www.eevblog.com EEVblog

        RCA is mostly made by SGS Thompson, a French firm.

        Yes, the name is owned by the Thomson group.
        I in fact used to work for the Thomson group (Thales).
        It’s a huge group, so could really be anyone, but probably TCL in China.

    • Zach

      I saw a vid with that device as well and immediately came to the same conclusion. Hopefully it might be cheaper than making a http://www.instructables.com/id/How-to-make-a-solar-iPodiPhone-charger-aka-Might/ which I made without the solar panel.

    • http://www.freeduino.de Jan

      these are product trolls, best to ignore them.
      all they want is what you just gave them: attention.

      btw. the battery version is probably a ripoff of the very successful minty boost by adafruit. i bet my ass that this got the same circuits inside. http://www.ladyada.net/make/mintyboost/

    • http://lost.co.nz/ Leon

      I don’t doubt that the WiFi name was thought up by some marketing monkey, but I’m one aspect of this story interests me: What level of EM power, across *all* frequencies, not just 2.4GHz, could a small antenna pick up in an active 21st century household? I guess you’d have to assume that you had a magical rectifier. (You could be really cheeky and put your wire up against an active 50Hz household supply…)

    • Brian Hoskins

      This smacks of those silly You Tube videos you see, except this time someone’s actually made a product out of it.

      I agree. Absolute crap.

    • http://kaqelec.dyndns.org Kathy Quinlan

      Hi Dave,

      I had a problem up until 8 odd minutes, but then you started talking efficiency :) I doubt you would charge it in 8 years ;)

      Also once you get over about 60 days for nicad, not sure what the figure is for Li based packs, the internal self discharge would be higher than the charging rate ;)

      Sigh when will the snake oil merchants give up ;)

      Regards,

      Kat.

      • Stephen Woolhead

        I was wondering what the internal discharge rate of the battery would be. Would be nice to have something like this you could charge from the mains, then throw in your bag and know that six months later when you need it it would still be charged.

        The shear number of blogs that have reposted this as a good workable idea though is some what shocking!

    • Jonathan

      I don’t know what the levels of a cell phone signal are but can this device harvest that?
      I don’t personally believe it will work even then but perhaps they believe the sheer number of sources will charge it?

    • Jo

      Hi,
      It could work if you put the antenna inside of a microwave at full power! :p
      Kids don

    • AskJacob

      If this thing even had a chance at being able to deliver, you would end up being torn limb from limb for creating a local blackspot for wifi around you, as it harvests a lot of the energy that was meant for distant wifi users….

      Pure snake oil product. My theory is – if it can’t even light an led, it ain’t gonna charge anything!

      They may as well sell us a super efficient solar panel with a light bulb for self illuminating perpetual electricity…

      Or perhaps a thermo-electric generator powered by the hot air coming out of the marketing department…

      Jacob

      • Brodieman

        I hear ya AJ – this is absolute rubbish. I’m honestly amazed how these are allowed to be manufactured and marketed!

    • Rastislav David

      I was browsing lt videos and found out this one:
      http://www.linear.com/designtools/video/ltchannel_energyharvesting.jsp

      Where different energy sources and how much can be extracted is explained. Starts on about 3:00

      Rasto

    • DaveL

      A research group at MIT has developed a functioning magnetic harmonic resonance induction system (shades of N. Tesla) that actually works. It is a long way from functioning on a broad scale. I did see a demo of the system that was used to power a wide screen plasma TV and an iphone. It can be done but perhaps not via WiFi.

      • George Herold

        Yup, I thought about that too. The MIT thing works in the near field and has a ‘relatively’ low frequency… a large wavelength. In the near field (I think) you can have a cross section that is much bigger than the physical size of the antenna… Then in the far field the cross section can be as large as the square of the wavelength (With a factor of pi somewhere.) But that’s almost exactly 10 cm. The number that Dave used.

        Well done Dave,

        George H.

      • nbsr

        It’s an interesting project but not for powering up home appliances. Anyone who argues it can be used for such purpose is not very different from these RCA guys.

        Both high-Q LC circuits are tuned so that their current phases are opposite. That cancels out (mostly, and only at a very near range) magnetic field between them. But, there is simply too much field being produced in the first place. Just think of how much energy has to be stored in the LC tanks so that after loading them with, say, 100W they still have a Q factor of ~100.

    • Norvog

      Hi, Dave!

      Saw an advert and it looks interesting: TI’s programmable watches with wireless interface and some sensors in it.
      http://focus.ti.com/graphics/tool/ez430-chronos_800.jpg
      http://focus.ti.com/docs/toolsw/folders/print/ez430-chronos.html

      The con I see is that you’re stuck with TI’s chips cause I guess they use SimpliciTI protocol for wireless connection. First time I’ve heard of it.
      And their way of reprogramming device is crappy! You should open it! Why not have wireless bootloader out of the box!!!

      So what do you think of it?

      • http://www.eevblog.com EEVblog

        Yeah, I’ve seen it and it’s quite neat and seems great value.
        Might have to get one just for the heck of it!

    • Neil

      Dave,

      There are a depressing number of these around at the moment. The BBC did an article on some device to bring the house mains voltage down to nominal volts. (In the UK that is 240V – generally the mains supply is a bit higher 247V typical).

      They started quoting all sorts of savings. Apparently a switch mode mains supply will save 30% energy. Now I’m forced to explain to people who don’t know the first thing about it how it will never save that much if anything at all.

      But it must do – it was on the news.

      Neil

    • Richard

      Ont thing you didnt mention is that wifi accesspoints are not transmitting all the time – only when needed other than a beacon.

      So unless you are downloading a lot (and not uploading, since that would mean it would be receiving more) the figures are gonna be even worse.

    • Mark

      Dear Dave,

      Don’t you mean cubic meters, not square meters?

      Mark

    • Mark

      Dave,

      If one were to build a perfect antenna that could absorb all frequencies of radio energy in the air, how much energy could one harvest? How much radio energy is in the air at any given time? Is there any way to measure this?

      Mark

    • Viewer

      Correct me if I’m wrong, but that isn’t even a constant 100mW. If you’ve got a digital signal, that’s intermittent by nature. Not to mention power is only present when a signal is being transmitted. An inactive router doesn’t give off much, if any, residual power.

      • http://www.eevblog.com EEVblog

        Correct, I was working with the ideal case just for argument.

    • Roy

      Well done, sir. I have been telling RCA (a subsidiary of Audiovox) that their story is nonsense. I have also told a number of journalists, some of whom have quoted me. I do chair an International Standards committee on Energy Harvesting and am applled at the damage that these stupid stories do to companies that have energy harvesting products that really work. I did manage to get a retraction out of Nokia in June wityh their similar story but RCA are proving more difficult.
      Please keep up the good work – bad science must be exposed

    • blipton

      What about the Palm Pre (induction?) charging?

      It’s wireless and doesn’t require 7 years to charge! What’s going on here?!

      • Sean

        Two coils, essentially an air coil transformer, and in close proximity. And a bit more than 100mW input.

    • Hamed

      hi dear Dave
      how are u today?
      i need to be a circuit which derived the shave machine (Philips)
      please sent its schematic
      tanks a lot

      • TrentO

        WTF is this?!!!

    • Steven

      Great video. ‘The free energy scams busted’ vidoes always bring a lot of negative comments from the ‘believers’ though.

      It seems more and more commonplace that people get sucked in by ‘overunity’ scams and the like.

      Another interesting one to look at is the EEstor cell, a 52kw/h ultracapacitor that can be charged in 3-5 minutes, apparently. It would be interesting if you could do a video blog on these sorts of technologies and their potential.

      always watching, keep it up!

    • John W.

      If you want to charge it really fast, just throw it in the microwave. ;)

      • TrentO

        I’m gonna buy one just to try this.

        No worries– I’m going to do it outside.

    • Dmitry

      Take a look at this:

      http://www.youtube.com/watch?v=csR8q5QttDw&feature=related

      Could you comment it? :)

      • http://quickplay.hostzi.com Th3_uN1Qu3

        That circuit does capture energy from radio waves, and it could even get 50 volts or higher. However once you put a load on it it will collapse because the current available is next to none.

        The mobile phone charging is just a hoax, he used an actual cellphone charger which wasn’t in the field of view of the camera.

        • http://www.eevblog.com EEVblog

          The mobile phone charging is not a hoax. The device contains a high capacity lithium ion battery that is perfectly capable of charging a phone. The battery was pre-charged and hence was able to charge the phone. There is nothing off-camera, that’s just silly. The hoax part is about the harvesting of the wifi energy to charge the battery.
          Dave.

    • Kelvin

      Dave this blog of yours sometimes remind me that having too much knowledge is bad. The majority of the people to stumble upon this product will probably say that the technology is cool and move along and never hear of it again due to the product failing before even hitting the mainstream.

      My friends usually give me “great” ideas about projects that no one has ever done before and I’m always the one to deliver the news that the idea won’t work because of the concept and physics won’t add up to a working product.

      I guess this is a disadvantage of being an engineer/scientist. Ignorance is a blizz as they say.

    • nbsr

      Dave,

      There are some real world applications of such energy harvesting but they are all limited to powering up things like autonomous single-chip systems (RFID’s, sensor networks etc).

      Your calculations are actually fairly accurate. People generally use dedicated larger power (0.5~4W) dedicated RF transmitters, directional transmitter antennas, but then there are losses in the rectifier circuit, reflections, longer distance etc. The circuit I worked on could actually produce ~100uW of DC power at 4m range, which was enough for supplying a rather non-trivial system.

    • http://www.hoevendesign.com Paul

      Has anyone tried to put the airnergy in a microwave oven? There should be enough 2.4GHz energy in there to make it work…

      It might even release the magic smoke.

    • pierre

      I think energy harvesting is a really nice tech which is spawning lots of cool devices, like microcontrollers, sensors, transmitters, which have nanowatt sleep power and can wake up and do their job using a tiny amount of energy… Lots of cool applications.

      But this one is just bullshit !