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posted by on Saturday February 04 2017, @03:56PM   Printer-friendly
from the just-add-plasma dept.

In today's odd science news, researchers have shown that they can produce electricity by evaporating water from a chunk of soot. The research falls into the category of systems that extract electricity from waste energy around us—kind of like generating electricity from swaying buildings or powering your watch from your own movements. But this was a result that I did not expect.

The experiments that make up the new work are so simple that pretty much anyone can do them themselves. Take a hydrocarbon of choice and set it on fire so that it burns with a yellow flame. Then hold a bit of glass in the flame so that it gets covered in soot. Afterward, expose the carbon to an atmospheric plasma. Tape some electrodes to the carbon and then lower it into some water. The porous carbon drags water into itself through capillary forces, and when the water later evaporates from the carbon surface, electricity is generated. Not much, admittedly, at 53nW per square centimeter, but still enough to raise eyebrows.

It turns out that there is a commonly known mechanism that could cause this effect. Water always has some ions in it, and as it flows, it drags these ions along. So you get an electric current associated with the flow of water. In this case, the flow is induced by evaporation, but you could get the same effect by making the water flow downward via gravity. Oddly, however, that flow isn't generating most of the electricity. By controlling where the evaporation could take place and measuring the current due to flow only, the researchers behind these experiments determined that the streaming water contributed about one-fifth of the total voltage.

It's pretty clear that the researchers themselves don't really understand where the charge is coming from, but they've made every effort to eliminate possible systematic errors. They used a fan to change the rate of evaporation, which showed that the voltage varied with the evaporation rate. They opened and shut the container to start and stop evaporation, which switched the voltage on and off as well. They used deionized water for most experiments, but they performed some with varying amounts of salt to show that the current was not simply due to ion contamination.

The team ran the experiment for hours, showing that as long as there was water to evaporate, the carbon sheet produced a voltage. They also placed multiple electrodes at different heights in the carbon sheet, and the voltage got progressively higher for electrodes higher on the carbon sheet. Current cut out when electrodes were placed beyond the height of the water column in the sheet.

So I'm pretty confident that the researchers are producing electricity—they even powered a small LCD display. But I don't understand why it works.

Source:

https://arstechnica.com/science/2017/02/scientists-produce-electricity-by-evaporating-water-from-a-chunk-of-soot/

Journal:

Guobin Xue, et al.,Water-evaporation-induced electricity with nanostructured carbon materials, Nature Nanotechnology (2017) doi:10.1038/nnano.2016.300


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  • (Score: 2) by opinionated_science on Saturday February 04 2017, @06:22PM

    by opinionated_science (4031) on Saturday February 04 2017, @06:22PM (#462892)

    it's physics and chemistry. Given 10^9 years, processes that operate on the 10^-12s timescale in a 10^10l of water, creates a massive(!) phase space to select for self-replicating molecules.

    That it happened is not as amazing, that it may have only happened once...in all time and space!

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  • (Score: 2) by Immerman on Saturday February 04 2017, @09:34PM

    by Immerman (3985) on Saturday February 04 2017, @09:34PM (#462942)

    I'm assuming you meant:
    >That it happened is not as amazing as that it may have only happened once...in all time and space!

    To which I say:
    Given how un-amazing it is that it happened, what would possibly make you believe something as preposterous as that it happened only once?

    With current technology it would be almost impossible to detect technological civilizations similar to our own around even the closest stars, much less life. For the vast majority of the stars in our galaxy a civilization would have to be shedding power at a rate to dwarf all but our most extravagant science fiction flights of fancy for us to have any chance of detecting them.

    And our galaxy is an infinitesimally tiny spec compared to the vastness of even the tiny bubble of the observable universe. And at those distances, for us to detect them a civilization would have to be wielding so much power that they might as well be gods.

    It's not impossible that we're the only life in the universe - but given the vastness of the universe, it seems akin to claiming that only those people you've personally met actually exist.