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UMD Researchers’ Wood-Based Technology Creates Electricity From Heat

posted by chromas on Sunday April 07 2019, @10:04PM   

upstart writes:

Submitted via IRC for takyon

UMD Researchers’ Wood-based Technology Creates Electricity from Heat

A University of Maryland-led team of researchers has created a heat-to-electricity device that runs on ions and which could someday harness the body’s heat to provide energy.

[...] This energy is generated using charged channel walls and other unique properties of the wood’s natural nanostructures. With this new wood-based technology, they can use a small temperature differential to efficiently generate ionic voltage, as demonstrated in a paper^[$] published March 25 in the journal Nature Materials.

[...] Trees grow channels that move water between the roots and the leaves. These are made up of fractally-smaller channels, and at the level of a single cell, channels just nanometers or less across. The team has harnessed these channels to regulate ions.

[...] A membrane, made of a thin slice of wood, was bordered by platinum electrodes, with sodium-based electrolyte infiltrated into the cellulose. The[y] regulate the ion flow inside the tiny channels and generate electrical signal. “The charged channel walls can establish an electrical field that appears on the nanofibers and thus help effectively regulate ion movement under a thermal gradient,” said Tian Li, first author of the paper.

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Original Submission

• Dubious Dubious (Score: 3, Insightful) by c0lo on Monday April 08 2019, @03:13AM (1 child)

  by c0lo (156) on Monday April 08 2019, @03:13AM (#826052) Journal

  TFAbstract [nature.com]

  After infiltrating electrolyte into the cellulosic membrane and applying an axial temperature gradient, the ionic conductor exhibits a thermal gradient ratio (analogous to the Seebeck coefficient in thermoelectrics) of 24 mV K^–1—more than twice the highest value reported until now.

  Assuming water as the transport for the ions, at the maximum temperature difference allowed, one will get a total voltage of 2.4V. Respectable value, not to be sneezed at, even if this is absolutely maximum.

  But ... no word about the shortcircuit current, or a characteristics diagram (voltage/current under different loads). Since the thermoelectric effect is realized in this case by sodium ion transport in solution (and not by electrons):

  1. I suspect the maximum current will abysmally low - the transport speed of ions in liquid is far lower than the electrons in the metals making a thermocouple.
  2. once the sodium ions are "chased away" from the "hot side" and reach the "cold" end, they'll need to be transported back to close the circuit - otherwise, the difference in the sodium concentration on the two faces (osmotic pressure) will soon cause the "ion pump" to stop. I have this feeling that work to get the "cold ions" back into the hot side will make the efficiency even lower

  Perhaps good enough for an thermocouple sensor exotic technology, but I really doubt that would be useful as a thermoelectric generator.

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  https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford

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• Re:Dubious (Score: 2) by leftover on Monday April 08 2019, @02:20PM

  by leftover (2448) on Monday April 08 2019, @02:20PM (#826164)

  Same thought here. Another "There is Voltage so there must be POWER!" We can keep hoping these fallacies are being spread by PR-types and not by the scientists themselves but they certainly seem to be more common.

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  Bent, folded, spindled, and mutilated.

  Parent