3 ms·

Scientists build circuit to generate limitless low-voltage power from graphene

22 points by danboarder 5y ago

Zenst 5y ago
>Knowing this, Thibado’s group built their circuit with two diodes for converting AC into a direct current (DC). With the diodes in opposition allowing the current to flow both ways, they provide separate paths through the circuit, producing a pulsing DC current that performs work on a load resistor. Always a bit hmmm when I see something simple like a rectifier spun out in a way that eludes that they invented some revolutionary new circuit.
- NavinF 5y ago
  Yeah this is hella sketchy. >We also found that the on-off, switch-like behavior of the diodes actually amplifies the power delivered, rather than reducing it, as previously thought Wat. Why is this crap on the front page?
  - danboarder 5y ago
    The journal paper is linked in the article if you want to read it. For low-voltage devices it seems reasonable to me. Fluctuation-induced current from freestanding graphene https://journals.aps.org/pre/abstract/10.1103/PhysRevE.102.042101 https://journals.aps.org/pre/abstract/10.1103/PhysRevE.102.0...
    - jbay808 5y ago
      Unfortunately I don't have an institutional login, or else I would be able to comment better. :( But it sounds to me from the abstract like the result is not significantly different from the thermal noise voltage on a resistor? I don't expect that they would be able to extract any work from the system, unless there is a temperature difference somewhere.
      - fsh 5y ago
        There is a version on the arXiv: https://arxiv.org/abs/2002.09947 https://arxiv.org/abs/2002.09947
gcanyon 5y ago
"clean, limitless, low-voltage power" the title omitted a pretty important word there.
- danboarder 5y ago
  Thanks - I added 'low-voltage' to the HN title even though it's not in the linked article because I agree with you, it's helpful.
danboarder 5y ago
"harvesting energy from graphene is controversial because it refutes physicist Richard Feynman’s well-known assertion that the thermal motion of atoms, known as Brownian motion, cannot do work. Thibado’s team found that at room temperature the thermal motion of graphene does in fact induce an alternating current (AC) in a circuit, an achievement thought to be impossible." So is this effectively a micro cooler? (Extracting thermal energy?) I experimented with TEC Peltier modules/cells for converting solar concentrator heat to electricity, it's not particularly efficient but it works when there is a sufficient temperature differential. https://en.m.wikipedia.org/?title=Peltier_device&redirect=no https://en.m.wikipedia.org/?title=Peltier_device&redirect=no
- grecy 5y ago
  Do you mind expanding on your experimentation? For an off-grid cabin in the Yukon I've always though about having a ton of TECs sitting on or very near the wood stove (which burns for 8+ months a year), with some piping and coolant running outside to a radiator (where it's -20C to -45C for 5+ months). I expect a least a few hundred degrees C of temperature difference, and I wonder about charging the batteries to augment the solar.
  - danboarder 5y ago
    As I recall the voltage was similar to a AA battery (per module) with a 30+ degree difference on each side of the cell, so a lot of modules could be assembled in an array to generate useful power. A lot of small boat/RV refrigerators use these for their direct thermal effect (one side will get ice cold when powered). My experiment was a smaller scale parabolic solar trough design with a line of modules along the focus point since I needed to heat water anyway to regulate temperatures in an aquaponics system (fish farm). Side note, I've seen successful systems out there that use Stirling engines to power a generator from the concentrated solar heat.
  - adrianN 5y ago
    With such a high differential you might reach better efficiencies using a Stirling motor.
WalterGR 5y ago
https://news.ycombinator.com/item?id=30494938 https://news.ycombinator.com/item?id=30494938

22 points by danboarder 5y ago

>Knowing this, Thibado’s group built their circuit with two diodes for converting AC into a direct current (DC). With the diodes in opposition allowing the current to flow both ways, they provide separate paths through the circuit, producing a pulsing DC current that performs work on a load resistor. Always a bit hmmm when I see something simple like a rectifier spun out in a way that eludes that they invented some revolutionary new circuit.

NavinF 5y ago
Yeah this is hella sketchy. >We also found that the on-off, switch-like behavior of the diodes actually amplifies the power delivered, rather than reducing it, as previously thought Wat. Why is this crap on the front page?
- danboarder 5y ago
  The journal paper is linked in the article if you want to read it. For low-voltage devices it seems reasonable to me. Fluctuation-induced current from freestanding graphene https://journals.aps.org/pre/abstract/10.1103/PhysRevE.102.042101 https://journals.aps.org/pre/abstract/10.1103/PhysRevE.102.0...
  - jbay808 5y ago
    Unfortunately I don't have an institutional login, or else I would be able to comment better. :( But it sounds to me from the abstract like the result is not significantly different from the thermal noise voltage on a resistor? I don't expect that they would be able to extract any work from the system, unless there is a temperature difference somewhere.
    - fsh 5y ago
      There is a version on the arXiv: https://arxiv.org/abs/2002.09947 https://arxiv.org/abs/2002.09947

gcanyon 5y ago

"clean, limitless, low-voltage power" the title omitted a pretty important word there.

danboarder 5y ago
Thanks - I added 'low-voltage' to the HN title even though it's not in the linked article because I agree with you, it's helpful.

danboarder 5y ago

"harvesting energy from graphene is controversial because it refutes physicist Richard Feynman’s well-known assertion that the thermal motion of atoms, known as Brownian motion, cannot do work. Thibado’s team found that at room temperature the thermal motion of graphene does in fact induce an alternating current (AC) in a circuit, an achievement thought to be impossible." So is this effectively a micro cooler? (Extracting thermal energy?) I experimented with TEC Peltier modules/cells for converting solar concentrator heat to electricity, it's not particularly efficient but it works when there is a sufficient temperature differential. https://en.m.wikipedia.org/?title=Peltier_device&redirect=no https://en.m.wikipedia.org/?title=Peltier_device&redirect=no

grecy 5y ago
Do you mind expanding on your experimentation? For an off-grid cabin in the Yukon I've always though about having a ton of TECs sitting on or very near the wood stove (which burns for 8+ months a year), with some piping and coolant running outside to a radiator (where it's -20C to -45C for 5+ months). I expect a least a few hundred degrees C of temperature difference, and I wonder about charging the batteries to augment the solar.
- danboarder 5y ago
  As I recall the voltage was similar to a AA battery (per module) with a 30+ degree difference on each side of the cell, so a lot of modules could be assembled in an array to generate useful power. A lot of small boat/RV refrigerators use these for their direct thermal effect (one side will get ice cold when powered). My experiment was a smaller scale parabolic solar trough design with a line of modules along the focus point since I needed to heat water anyway to regulate temperatures in an aquaponics system (fish farm). Side note, I've seen successful systems out there that use Stirling engines to power a generator from the concentrated solar heat.
- adrianN 5y ago
  With such a high differential you might reach better efficiencies using a Stirling motor.

WalterGR 5y ago

https://news.ycombinator.com/item?id=30494938 https://news.ycombinator.com/item?id=30494938