The Roots of Power: How Voltree is Tapping Tree Energy to Save Forests | Hacker News Reader

The Roots of Power: How Voltree is Tapping Tree Energy to Save Forests

xconomy.com

39 pointsrfreierman13 comments

Brief summary: If you stick an electrode into a tree and another into the ground around it, the pH difference between the two media gives you a difference in potential (~ 0.1V); you can draw a small current from this. (The article doesn't indicate how much current. That seems kinda important.) It's enough to power small sensors attached to the trees, which communicate wirelessly with a base station. They hope to use this to monitor conditions in forests so as to spot, or anticipate, or prevent, forest fires.

Despite the cutesy closing line calling Voltree a "green-energy company", there is no prospect whatever of getting energy from trees to power household appliances or anything like that. (Nor does anyone claim there is.)

Seems very neat, though.

As I recall current is related to the size and shape of the electrodes, potential is related to PH and the makeup of the electrodes. So you can't really say what the current is without standardizing on a specific device.

I'd have thought that there'd be a maximum current you could draw without making the potentials equalize. For small electrodes, the resistance between the electrode and what it's connected to will be a limitation, but beyond a certain point I'd expect it'll level off, the level basically being determined by how much the tree's internal workings are doing to maintain its pH level.

I was thinking the same thing. I'd like to set up a 3000 watt system in the middle of the forest, right now it's looking like $35,000 for solar & misc parts. If I could get it from trees though... I'm tempted to take an ohm meter to work tomorrow.

A 10 HP steam engine should do you. It's going to take a fair number of trees to fuel.

I actually heard about this a long time ago, you can apparently make a crude battery out of potted plants by connecting Plant A to the pot of Plant B and B to the pot of C and so on. With a common ground, like a national park this likely wouldn't work. However, connecting 500 trees in parallel rather than series could provide a high current, which you could then run that high DC current through an inverter and transformer and pump it up to whatever voltage you need.

However, I'm not sure how practical connecting hundreds of trees in series would be as you're going to get the problem of animals and what not. Unless you wedged your electrodes in good, or found a way to allow the tree to grow through them and hold them in place, you'd get trouble with squirrels pulling them out trying to run on the wires and other crazy stuff.

Watts, volts, amperes, size and capacity are all related. My point was a sapling and a 100 year old tree are not going to have different capacity, but they probably have about the same PH spread so they would have the same voltage. My guess is you are only going to be able to extract a small fraction of the energy you would get from burning the tree but you get to extract it over a long time period.

Over a short period of time you'd never get the same amount of energy out. However, if you get an average ~20milliwatts of power from a tree throughout a 100 year life time, when you'll get over 17 kilowatt hours of power from a single plant.

However, the real question like with all green power sources is how much land it uses up.

As Kim Stanley Robinson pointed out in his Mars trilogy of books, renewable energy is actually a type of geoforming. The more windturbines we build, the more we effect the flow distributions of winds. Quite literally, if we supplied all of Earths power needs by wind then there'd be so many turbines over the planet that we would begin preventing near-ground airflow.

Equally, at current efficiencies you'd have to cover all the land on the planet to even remotely hope of powering human civilization and in the process you'd destroy all life on Earth. Finally, tree powered Humanity would be kind of cool, but again you'd cover the entire planet in trees and harvest power at much lower efficiencies than solar.

So, in the case of tree power you're much better off doing what some power plants are. Use fast-growing trees, cut them down every 6 months and burn them. It's actually been shown that growing and burning trees produces less CO2 than growing them sequesters, although in the long run unless you put all the leaves and what not in a mine they'll eventually rot and get back into the air or end up in a forest fire or compost or some such eventually making it carbon neutral.

If one believes your summary, this thing is pretty silly. Why not stick a god damned battery on those devices?!

Meaning... you'll need 15 trees in your backyard to power a small flashlight? So if you owned a forest with a few thousand trees, you might have enough voltage to power 4 lights in your home at the SAME TIME? AMAZING!

Apart from the coolness of its subject, this article has a real cliffhanger of a page turner. It's probably inadvertent, of course - but I dare you to resist clicking "Next Page" :)

That was just cruel.

Ha, I noticed that as well, overall the story was well put together and informative.

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