Harvest Energy from Air? Ha!

One of our contributing editors, Elizabeth Montalbono, wrote a blog for another UBM site, Design News, about harvesting energy from the air. A major discussion ensued. I had initially hoped this had to do with the electrostatic gradient in the air or the Earth's magnetic field. But it did not.

Instead, the post had to do with a proposal by Dennis Siegel, a student at the University of Arts in Bremen, Germany, to tap the energy available in the E-M fields around high-tension power lines, radio broadcast towers, cellphones, and electric appliances. The intent was to draw just a small amount of energy to charge a small battery, for example, that could be used to power a cellphone, flashlight, or radio.

With regard to using small appliances as the power source, the assumption is made that the appliance has a motor, or that it has an internal power supply that uses a transformer. Either way, the stray magnetic field that leaks out would be intercepted with an open frame inductor. Of course, the coupling is rather loose, so the energy transfer level would be pretty low, and the charge time would be pretty long. Siegel notes this but says it is still a workable idea.

My first impression was that, if you could increase the coupling coefficient, that would help. Then, in an a-ha moment, I thought, “If you're that close to the appliance, couldn't you just plug a wall wart into the power mains?” That would increase the coupling coefficient substantially (like to unity). If you're just trickle-charging a small battery, the cost of the electricity used would be practically nil.

But that's not what really got me concerned about this method of getting power. Apparently, Siegel thinks harvesting energy from utility power lines and radio transmitters is a perfectly OK idea with no consequences. And a significant number of the people who commented on the blog also think it's perfectly OK. The assumption is that the field is there whether we snag it or not, and that you can couple to the power line inductively, capacitively, or not at all — there's no effect on the utility's power distribution. This was clearly thought up by someone who had not paid attention during an AC Circuits 201 class.

As for harvesting energy from a nearby radio station, I guess that same someone was not paying attention during RF Circuits 301. We could conduct an experiment: Buy a house in the northern suburbs of Cincinnati, and build a nice vertical antenna tuned to 700kHz. Add a center loading coil, so the antenna doesn't have to be quite so tall. From its base feed point, couple it into a suitable transformer matching network, rectifier diodes, and filter capacitors. Et voila — free electricity.

Just let me know how long it takes before the chief engineer and an attorney from WLW knock on your door.

40 comments on “Harvest Energy from Air? Ha!

  1. eafpres
    March 25, 2013

    @Brad–are you suggesting that extracting energy from the field of a source might appear as a load on the source, and thereby change the entire system?  

    For instance, coupling to the power line and running your hot tub might show up as an unexplained loss to the power company (OK, if you and a bunch of your neighbors did it all at once), and if you inadvertently took all the power from, say, one phase of a multiphase transmission line that it would become unbalanced?

    For the radio station example, would you suggest that erecting a well matched antenna of similar gain to the broadcasting antenna and drawing power from it might alter the efficiency of the broadcast source, or alter the radiation pattern, perhpas causing interference patterns and complete service outages for some other customers?

  2. Netcrawl
    March 25, 2013

    Thanks for bringing us this wonderful story about this perpertual motion machine, it seem a workable idea! I think I already heard this guy, it could be @Scott I think must be in hot pursuit. Trying to make a moonshot.

  3. goafrit2
    March 26, 2013

    Not really a good idea – does it mean one has to live close to HV transmission lines just because of few dollars a year. I will not trade my life that cheap.

  4. goafrit2
    March 26, 2013

    >>  and if you inadvertently took all the power from, say, one phase of a multiphase transmission line that it would become unbalanced?

    Are there not radiation risks associated with living in such places where you can harvest this power?

  5. goafrit2
    March 26, 2013

    >> Just let me know how long it takes before the chief engineer and an attorney from WLW knock on your door.

    There is that illusion that energy could be free because there is no connection. As you rightly noted, harvest it and the lawyers will knock on the door.

  6. Brad Albing
    March 26, 2013

    This is why we where our al-foil caps. Well, that and so the guys in the black helicopters can't read our thoughts.

  7. Brad Albing
    March 26, 2013

    Probably not – based on studies I've heard about but not read personally. There are lots of people that live near High-V transmission lines and they seem to still be OK. So probably it's safe.

  8. Brad Albing
    March 26, 2013

    The guys that are talking about pepetual motion machines (PMM) are the same ones who show up on those clear channel AM radio stations at 4:00AM and discuss UFOs. Hmm… seems to be a connection here.

  9. Brad Albing
    March 27, 2013

    Yep – tapping water or gasoline from a pipe – obviously stealing. Grabbing energy out of the air – it's there already, whether I grab it or not, so it's not stealing. Sort of like if the water or gasoline were leaking from the pipe and all you did was collect it before it soaked into the ground.

  10. dtl1606
    March 27, 2013

    I think the telling thing is where the student, Dennis Siegel is studying – the University of Arts in Bremen, Germany.   Nothing wrong with German universities, but he's at a university of arts.   This is a bit like asking a programmer to write and aria!

  11. srm_creator
    March 27, 2013

    Once the energy is in the air, it is free as long as it enters your property.

     If you feel you can harvest any useful amount of energy, go ahead! Make my day!

    However, as it was pointed out (not paying attention in your high school science classes), the amount of energy available is so minute……My grandchildren will be old by the time you have “harvested” enough energy to re-charge even one cell phone.

    Cell phones, radio receivers, TVs, need to use electricity from the grid TO AMPLIFY those weak signals to be able to show you the content. What makes these people think they can harvest energy from those fields?

    If there was enough energy there, why then do we amplify the signals?

    Why re-charge? No need to harvest! Just make battery-less cell phones, battery-less radio and TV sets that can run on the energy harvested from the air waves, right?

    It is amazing to read some comments from people that appear never to have gone through engineering college. And if they did, how did they manage to pass examinations?

  12. David.Fischi
    March 27, 2013

    At first, I thought you might be referring to an article I saw in ScienceDaily, “Discovery May Allow Scientists to Make Fuel from Carbon Dioxide in the Atmosphere”.  The Design News article is just silly filler.

  13. Guru of Grounding
    March 27, 2013

    This kind of stuff belongs on the Discovery Channel, where the treatment of science is so superficial as to be insulting to anyone with a brain. And it's further proof that the general public is being dumbed-down by car crash/explosion “entertainment” posing as science. Even the Science Channel seems to be caving to this crap. The “art college” background of the “idea” reminds me of all the absurd audiophile projects and “experts” on the internet coming from folks with degrees in marine biology, or polish literature, or somesuch. The whole subject certainly qualifies as “noise” as stated in the Planet Analog banner “All Signal No Noise” … just my 2-cents worth!

  14. Brad Albing
    March 27, 2013

    Quite so – except for the example of living near WLW, et al.; and then you'll noticeably change their transmission and they will notice.

  15. Brad Albing
    March 27, 2013

    I agree – the seeds of our destruction – Discovery Channel-type science expalnations and audiophile snake oil salesmen. I feel another blog topic rumbling in my gut.

  16. Brad Albing
    March 27, 2013

    Now don't speak poorly of code crunchers. Even tho' they are not analog engineers, I am sure that there is 1 (or perhaps 2) out there that could string some musical notes or chords together and produce something pleasant. Or if not, they could write a program to do it for them.

  17. Brad Albing
    March 27, 2013

    Oh, I'd overlooked that in my original post. Those who can, engineer things. Those who can't, teach engineers to design things. Those who can't teach, go to art school.

  18. Gregst
    March 27, 2013

    Have you ever built a detector radio ? The energy (in microwatts) was sufficient to drive the high-ohmic headphones.

    Imagine a space where the RF energy is uniformly distributed. Put an antenna array in that space. Connect the array to the detector radios. Hook the outputs in parallel. You should get some sizeable current. Theoretically, for 1000 antennae, you should get energy in watts.

    If an attorney comes, tell him to buzz off because you are collecting non-specific RF energy, including energy of atmospheric electricity. Tell him that the collection of energy is done at the points where that energy would be wasted anyway, i.e., absorbed by the environment. Tell him that your antennae reflect that energy much better than the surroundings. If he sues, you would become famous, for that would be similar to “monkey trials”, those trials in the South against the evolution.

  19. srm_creator
    March 27, 2013

    As several of you have noticed, there appears to be a trend with these nonsense articles about harvesting energy from the air, or making processes “more efficient” than Nature's processes….

    Here you have one prime example:

    Some people think they can “extract” fuel from atmospheric CO2. Of course they don't tell us that it will be several times more expensive than extracting it from fossil fuels, or from coal mines.

  20. Brad Albing
    March 27, 2013

    Fuel from carbon dioxide? Wouldn't you need to brek the molecule apart to get at the carbon? (Yes) How much energy would that take?

  21. Brad Albing
    March 27, 2013

    Umm – I'll say, you tell him to buzz off. Or more specifically, tell your “non-specific energy” claims to the judge. He will fine you a non-specific number of years and fine you a non-specific number of dollars.


  22. Brad Albing
    March 27, 2013

    An addendum: If you really used an extremely broad-band antenna (no tuning – just a giant window screen/mesh/apparatus) then perhaps you would in fact not interfere with the local radio stations (but I think you still would somewhat). But you would also collect negligible amounts of useful/usable energy. Unless you are trying to collect current from the atmospheric voltage gradient. Then maybe.

  23. Brad Albing
    March 27, 2013

    Just one more thing. You should take the position that I am completly wrong – that I have no knowledge on the subject at hand. And you should go ahead and put up some sort of antenna or antennas with suitable diode networks. Let us know what happens next.

  24. Gregst
    March 27, 2013

    I (and my kid, whom I taugh how to build detector radios) did such an experiment about 7 years ago. We built a couple of detector radios, tuned them to a local AM station and hooked them in parallel to an RMS ampermeter/voltmeter. The output voltage was about 2.3 V (0.7 V drop attributed to the diode). The total power per a detector radio was about 15 microwatts. As we increased the number of these radios hooked in parallel, the power on the meter was increasing proportionally. I do not know what is a minimal distance between the antennae  that would still allow an effective energy harvesting.

    Try it yourself. All that you need, are the wires and germanium (do not use silicon !) diodes. Maybe, some caps as well, if you want to have a tank to tune to a particular RF station.

    I thought that the energy was sufficient to trickle charge a battery.

  25. Brooks Lyman
    March 27, 2013

    As has been pointed out, a simple diode detector (“crystal set”) radio will provide enough power from the antenna to run a pair of headphones (at least the old, 2KΩ impedance ones).  A number of years back, there were several curcuits that appeared in magazines like popular electronics that put a rectifier/filter circuit in parallel with the signal detector circuit and garnered enough power to run a more sophisticated receiver, with a small speaker (I doubt that the volume would be up to modern teen-age rock and roll music standards).

    Given the varying sensitivity of the input stages of broadcast receivers, not to mention other loss sources, both natural and manmade, I rather doubt that one would be getting any visits from the radio station's lawyers for trying the above mentioned trick.  Of course, setting up a matching antenna/rectifier system right next to the transmitter would make it possible to steal a fair amount of power, and that would more than likely be illegal.

  26. Gregst
    March 27, 2013

    A lot of Americans are overweight, lots of dead energy is stored in fat. How about making them to exercise by winding up springs driving the electrical generators ?

    Whoa! a infinite source of energy and such an improvement in the public health! Let's call it “fat harvesting.”

  27. Brad Albing
    March 27, 2013

    OK, well that actually would be a good idea if we all moved around more.

  28. Brad Albing
    March 27, 2013

    You could trickle charge a battery – it would probably take longer than you care to wait. Beyond just you doing this via an antenna farm in your backyard, consider what would happen if a lot of people in your neighbor hood or town did this. It would cause an attenuation of the transmitted signal. Apart from what I said earlier about an attorney knocking at your door, there would be less available energy for everyone who was erecting antennas with the resultant longer and longer charge-times for everyone's batteries.

  29. Gregst
    March 27, 2013

    Dear Brad,

    Imagine, you have a transmitter, and you erected an omnidirectional (isotropic) antenna. It radiates energy towards any point in space. Whether you are receiving a signal at that point of space, or not, the energy is radiated anyway. If you do not obscure/shield that radiation, you cannot interfere with anyone's reception. What happens to the energy that is radiated yet not used by the receivers ? It is partially reflected and partially absorbed by the surroundings. If on the surface of that surroundings you erect an antenna that does not obscure the other antennae, the RF energy would partially reflect and partially penetrate it. If the antenna is connected to a receiver, or other energy-transducing apparatus, that penetrating energy would be used for something useful, otherwise it would turn into heat. Since antenna is metallic, it would better reflect the energy than non-metallic surroundings. So, we are talking about harvesting of the unused, throw-away anergy, not about stealing of energy. Stealing could be caused only by shielding. No shielding – no stealing. A metal or metalloconcrete bridge would steal incomparably more energy than your antenna. 

  30. Brad Albing
    March 27, 2013

    I agree with that. I'm just saying that to grab usable amounts of RF energy from the air (enought to charge a battery or light a lamp) would start noticably affecting the radiated signal. Stated the other way around, doing something that no one at the radio ststion notced/cared about would not give you enough juice to warrant the time and money you spent to do it.

  31. DadOf3TeenieBoppers
    March 28, 2013

    The so called stray fields are not so stray. The energy the power lines put out returns to them; it taken by open loop inductors, it is a loss to the power companies. Borrowing energy from a radio transmitter close to it reduces its range.

    Advocating the use of this 'stray' energy to charge batteries or anything else is advocating theft.

    On the other hand, using the decompression of natural gas from the high pressure feeders to the low pressure supply into a building, or the flow of water from a water meter into a house, to generate a hundred milliwatts is legitimate since the suppliers are not expecting any of it to return to them, and in fact charge the customer for the energy to provide it in the first place.

  32. Brad Albing
    March 28, 2013

    Good point on the return of the energy to the power lines due to the inductance. I should have mentioned that.

  33. Brad Albing
    March 28, 2013

    For the water & gas meter example, I think the water and gas meter manufacturers were looking at that as a possible power source for some of the “smart” meters. Supplemented by a rechargable battery or super cap.

  34. goafrit2
    April 13, 2013

    >> There are lots of people that live near High-V transmission lines and they seem to still be OK. So probably  it's safe.

    I hope so but some movies put fear in me. I watched one that noted that in a certain school, all the graduates were going bald after a certain age and they wanted to know why? It turned out that there was a satellite dish in the school which turned out to be a hanging spot and that was the reason! Yes, a movie but it could have some truth.

  35. goafrit2
    April 13, 2013

    >> Grabbing energy out of the air – it's there already, whether I grab it or not, so it's not stealing.

    It seems you are looking at IP within the framework of the 19th century. Nothing is free. If that line has not been there, the guy would not have tapped. So, it cost money to be created and needs to be paid for. Information is a “matter” and is costs resources. I think tapping HV line signal is a violation of IP. No one will sue until your P&L gets the interest of Wall Street. Then the person will know it is wrong.

  36. goafrit2
    April 13, 2013

    >> Nothing wrong with German universities, but he's at a university of arts.  

    Do not be worried by the name of the schools in EU. They may be building cars in that school. The name is not an issue.

  37. goafrit2
    April 13, 2013

    >> Why re-charge? No need to harvest! Just make battery-less cell phones, battery-less radio and TV sets that can run on the energy harvested from the air waves, right?

    Ideally it is an illusion to think that power under HV transmission line is free. Make money out of it and you will see that IP attorneys are everywhere in America. There is no need to worry now as there is no one making good money in it. But wait until the bank begins to roll.

  38. goafrit2
    April 13, 2013

    >> My grandchildren will be old by the time you have “harvested” enough energy to re-charge even one cell phone.

    There is no need to bet against innovation. If this shows promise, people can put money and get it down within five years. The big question is > even if you do it, how will you monetize it?> That may be the reason no one has commercialized it.

  39. goafrit2
    April 27, 2013

    >> The guys that are talking about pepetual motion machines (PMM) are the same ones who show up on those clear channel AM radio stations at 4:00AM and discuss UFOs. Hmm.

    As a kid I was fascinated with UFOs because some of the claimed images seem factful and believable. Yet, it seems nothing is happening there for someone to feed my intrigues with more realities. Men have ways to build connections to make a living and who will blame them? Like watching some TV stations that run 80% of gold related ads with the anchors telling you that gold is the best hedge to dollar!

  40. goafrit2
    May 2, 2013

    >> Sort of like if the water or gasoline were leaking  from the pipe and all you did was collect it before it soaked into the ground.

    I like the thinking…but make some big bucks in it. Some smart lawyers will help everyone understand that signals are physical entities just as information is “physical”. In this America, nothing is free. You cannot tap water from a pipe and get into trouble, tap TV signals get into trouble and yet tap mains signals and not. Until you make money in it, no one cares and that is the state now.

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