Tapping Tree Power

[bugloaf] tipped us off about this flower power hack. University of Washington researchers, [Babak], [Brian], and [Carlton] have developed very low power circuits to run directly off of trees. This builds upon the work of MIT researchers and Voltree Power. A voltage of up to around 200mV is generated between an electrode in a tree and an electrode in the ground. Identical metals can be used as electrodes as the process is not like that of a lemon or potato battery. The significant development here is the use of a boost converter and exceptionally low power circuits. What kind of applications can you come up with for this source of power? Maybe you could try to combine this power with the power from donuts and hair.


  1. sean says:

    I bet there’s a difference in power output of the tree (that just feels weird saying) between winter and summer, where summer you would get more power because it is more active in photosynthesis and during the winter it’s more dormant

  2. Don Cross says:

    I’m a bit curious about any claim that this small voltage is being generated by the tree, even given that the two electrodes are made of identical metals. I recently did an experiment where I was trying to measure the electrical resistance of soil between two identical aluminum posts pounded into the ground about a meter apart. My efforts were frustrated because I was measuring very different resistances depending on which way I hooked up the ohmmeter. When I switched over to measuring voltage, I discovered why: there was about 0.15 volts of potential appearing across the rods. I figure some kind of differential galvanic effect was taking place. Even though the metal was the same, the soil (electrolytes?) were different in the two spots. Might the tree and soil simply be corroding the two nails at different rates, thus acting like a battery?

    • chris jones says:

      This effect was used a long time ago (1800’s).
      I forget what its called but I’m pretty sure they used it to power telegraph stations.
      It works better if the ground stakes are north and south of each other along magnetic meridians.
      Its not galvanic.
      The farther apart the stakes are the higher the voltage but there comes a point where the resistance of a wire joining them to form a circuit negates the voltage gain.
      You may be able to connect several pairs of stakes in series and use them to charge a low voltage super capacitor to light an LED.

  3. R.Eulberg says:

    Conceivably, one could hook up quite a few joule-thieves for a pixie-lit grove…

  4. Saf says:

    Hmm interesting, sounds perfect for tree cctv & microphones, linked via wifi to national forest websites etc. Great tourism tool lol (not to mention great spy tools for big brother ;P).

    Not saying one cctv or mic per tree, but one per 10 or so trees powering the one device?

    • chris jones says:

      There’s a pilot project of remote smart sensors to monitor temperature, humidity, etc., and send out the info to a collecting station for forest fire danger potential somewhere in the USA. Also I believe the US and probably other militaries are looking at security remote sensors in tree powered (bush, weed? powered)technology.
      Its not galvanic and its claimed that the power will last until the tree dies.
      The world is getting smaller.

  5. andrew says:

    Maybe that’s why we darkened the sky in the war against the machines…

  6. Jack says:

    @Saf – Please don’t give anyone any ideas…. That’s the last straw for me – the moment governments start monitoring parks and wilderness with AV, I’m leaving the developed world to hopefully somewhere remote that doesn’t already do it because of poaching problems. sigh…

  7. andrew says:
  8. s0crates82 says:

    remote area weather sensors, connected by some sort of bluetooth or wifi mimo mesh network.

    i dunno, 200mv ain’t much, especially when it may be way lower in fall/winter.

  9. Ragnar says:

    While 200mV already isn’t much, the nanowatts that you can work with are even less desirable when you want some wireless application.

  10. ACID says:

    Until the tree (or one next to it) gets struck by lightning.

    I’m guessing this is related to natural static charge based on elevation, plus insulative properties of wood. Smart idea. Now shield it from massive surges and you may have something. That’s one thing about natural sources of power – they can vary drastically.

  11. Joel says:

    Security system.

    A paranoid billionaire with lots of forested property would want to know when someone enters, but be unobtrusive about it.

    ACID: “I’m guessing this is related to natural static charge based on elevation”

    My guess is it taps power from the ion pumps that drive water into the tree’s roots. Sort of like the power system from The Matrix, except possible.

  12. Daniel says:

    I am sorry about this, I am:

    this is…



  13. anon says:

    It’s all fun and games until the trees decide they want their power back.

  14. Chalkbot says:

    Don’t you mean “Abso-rootly Tree-rific?”

  15. fjsdkl says:

    The difference is caused by the tree – it’s simple plant biology.

  16. telephoneman says:

    Lol anon.

    i remember reading awhile back about potential diffrences between same metal (steel) plates driven into the ground somewhere. It had kind of a nikola tesla feel to it lol.

  17. aztraph says:

    if you do tap into the tree’s free electrons released during photosynthesis, does the tree get harmed or will it eventually die? has anyone tried to figure out how much photoelectric power a tree produces? how much can it spare before it starts to starve? any suggestions?

  18. DanAdamKOF says:

    Don’t certain metals kill trees? I remember hearing before that hammering big brass and/or copper nails into a tree trunk eventually kills it.

    If so you’d have to pick your electrodes carefully.

  19. Hirudinea says:

    I have no idea what you’ed use this for but I’m sure someone will hook it up to f*#king twitter!

  20. malluck says:

    What are the chances they’re really just using the long wires as antennas and harvesting power from radio emissions?

  21. Peter says:

    Low powered wireless devices. Use the differential to charge up something and discharge it every 10 mins or 60 mins or whatever to send some small amount of data to a nearby receiver.

    You could use it to monitor temperatures or light levels for example.

  22. Leigh says:

    Read about this ages ago.


    My house is surrounded by trees. I think I could get a buzz out of using all the trees to power my house :)

  23. Patrick says:

    Can I use it to power an arduino?

  24. Pilotgeek says:

    @Don Cross: Of course the soil has electrolytes, it’s what plants crave!
    Brawndo, the thirst mutilator!
    I would hook up low power clocks to trees in random places to confuse people.

  25. Brett says:

    Sure, it’s .2V, but did anyone catch a max current value? .2V would be plenty to do cool stuff with (with a boost converter), but only if you had quite a bit of current.

  26. Matt says:

    I guess you could say it was sapping energy!

    I’ve just twigged what they are doing now!

    Seriously, you have to bow down to these guys!

    Shall we leaf out the tree jokes now?

  27. Pilotgeek says:

    Dammit, I had to get out instantrimshot.com

  28. Richard says:

    It’s pretty easy to tell if the power they’re obtaining is simply received RF – stick an oscilloscope on the raw terminals before the ‘power’ is processed in any way… if you can see an AC waveform, you know it’s neither electrolytic or ionic in origin.
    If there’s a clean waveform, it should be fairly trivial to trace it back to source and see where the power is really coming from.
    If it’s truly DC, then it should be possible to figure out the chemistry of what’s going on and see if it’s sustainable – it’s certainly not ‘free energy’, as there’s no way it will ever recoup the energy already invested in creating the electrodes and associated circuitry.

    Most of the time in this country (England) we’d be able to tap a lot more power from the mechanical motion of a tree as it sways in the wind – I’m close to the west coast and completely wind-free days are very rare indeed.

    What do you folks reckon is the best way to gather energy from a moving tree, that doesn’t harm the tree, and can cope with huge variations in both the degree and direction of movement?

  29. threepointone says:

    It’s most likely because of an ion gradient produced by the tree between the ground and the inside of the tree. Trees absorb metal ions.

    It should have already been pretty obvious that you can’t suck much energy out of the tree (only really useful for low power sensor applications), but this also means you have to be careful–by drawing a current, you may be damaging the health of the tree by fighting against its attempts to pump necessary minerals from the soil.

    I’m somewhat curious as to what low voltage circuits they have in mind. There’s only been two real techniques (without requiring some complicated outside energy source, such as flicking a switch and using the inductive boost to start a step-up converter) i’ve seen that can boost voltages below .7v (usual limit with silicon devices)–use old germanium transistors (NTC or whatever that company was called sells ‘em) or use ALD’s special zero-voltage gate threshold MOSFETS (real cool stuff, btw)

  30. _matt says:


    Because Brawndo has electrolytes!
    it all makes sense now

  31. strider_mt2k says:

    Oh man, my project says it requires tree batteries, but I only have two. :(

  32. Doom2099 says:

    sounds like a mud battery.
    with the right electrodes you can tap into almost anything.

  33. ruster says:

    @andrew pioneer park is in downtown slc and used to be a big druggie and hooker hang out. the cameras are an enforcement measure. I don’t love big brother either, but that park was useless for humans due to the human debris there.

    as for the article. stupid hippies, buy a battery and a solar panel.

  34. Shadyman says:

    Enough with the tree puns! You guys are treerible!

  35. coldwar23 says:

    After the old toilet paper tube radio we all built, I was thinking a massive array of germanium diodes would turn those massive amounts of radio waves into microvoltages, effectively recycling radio wave energy.

    Dunno, any ideas?

  36. Jimbo says:

    How about recording the pattern of swaying of the trees as it is generated by wind movement over an entire forest with accelerometers stuck up the trunks? :-)

  37. Frogz says:

    hm, i’ve looked everywhere i could within a 30 second period but i found no mention of current anywhere
    you can have a billion watts at .2 volts if you have enough current
    or it can be barely enough to be detectable by expensive lab equipment
    anyone know what kinda tree-mendous POWER they are getting out of this?
    (on another note, we should all be shot for all these tree puns/jokes)

  38. uC says:


    Check these guys out:

    RF power harvesting


    Ti is getting very interested in this stuff (It’s where I heard about it )


  39. therian says:

    Take a multimeter probes in both hands, do you see .1V ~ .3 V ? now try to touch other parts with probes, see more voltage ? No
    you not a super man you a fitly pig, go wash yourself you sweat start electro-chemical rections

  40. Orv says:

    @Don: If this was near a building you may have been seeing ground currents from the power system…because of the bulk resistance of the earth any ground current will create a voltage gradient.

  41. Read how I built my own Solar Panels for under $100 at Ambigrid Review!

  42. strider_mt2k says:

    Ambigrid Review’s solar panels use PEOPLE!

  43. Don Cross says:

    @Orv: That is an interesting possibility. I should try it again and put the voltmeter in AC mode. I could also hook up some high impedance crystal earphones and listen for 60Hz hum.

  44. I used the Ambigrid Plans to build a solar pales for under $100, as well as a solar water heater for less than $10! I can’t say enough good things about them!

  45. monkeyslayer56 says:

    arduino + many tress= soon to be hack on hackaday…

  46. Yrb says:

    It would be interesting to create a device that is powered by human beings.. then we create a huged field of humans and connect their minds to a big computer.

    That might work!

  47. I used the Ambigrid Plans to build a solar pales for under $100, as well as a solar water heater for less than $10! I can’t say enough good things about them!

  48. browncardboard says:

    @ Frogz they are producing power in the microwatts to nano watts scale.

    This company voltree is actually a direct competitor to my company & they are doing some great work too :)

    The way that they generate power is similar to a microbial fuel cell. Although power would be augmented by a galvanic reaction [galvanized nail electron doner like a patato battery] they claim to not actually be consuming any of their electrodes.

    They are slim on details, but I believe they are capitalizing on the ph gradient that forms between the inside of the tree and the surrounding soil. I would guess that it is just a concentration gradient that they are capitalizing on.

    In terms of the power electronics… 0.2V coming out in the micro watt scale is not a lot of power and really difficult to work with. I have yet to find any commercially available power converter solution that can boot strap from that level. It is only recently that that amount of power would even be considered to be useful.

    We are continuing to develop a power converter that can boot strap from 0.3v and a little lower to a usable voltage. At these tiny voltages, you are close to the threshold tolerances of many of our components, its not easy.

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