Physicists Build Circuit That Generates Clean, Limitless Power from Graphene

Without getting all quantum about it, it seems to work by configuring the graphene as one electrode (or both) of a capacitor. As the graphene flaps in the breeze (actually Brownian motion, I assume), the changing geometry will change the capacitance. If there is a charge on the cap, then the voltage would flap too, inversely (Q = CV). A changing voltage would tend to push about a current (i.e. charge motion). If their diodes somehow have a negligible forward voltage drop, then brief moments of higher voltage on the flappy cap would push increments of charge onto the storage cap (the one to the right of the diodes) until the storage cap voltage rose to equal the peak flappy voltage (minus the diode voltage drop). When the storage capacitance is greater than the flappy graphene capacitance, the stored energy will be greater than the tiny increments (energy = 1/2 CV^2). Then every so often the storage cap could be switched to drive some load.

So why would there be a charge in the flappy capacitor? Well, a bias voltage is applied by this battery in the circuit. Ahem, before invoking any principles of thermodynamics, I'd like to see some detailed measurements, or even careful theory, of the current out of the battery and back into the battery, particularly w.r.t. the instantaneous voltages (P = VI), to prove that the time-average power delivered by the battery is precisely zero, or at least far lower than that putatively transferred to the load (light bulb in the animation). Otherwise it's behold, we found a high-resistance path for our battery to run a light bulb.

There is some precedent for semiconductor thermal magic in the Peltier junction. It makes one end colder and the other end hotter by applying electric watts to it, with no moving parts aside from the electrons and holes recombining, or something. But nobody sees thermodynamics being violated or extended there.

But here the magic is to take away thermal energy from one place, the flappy graphene (thereby cooling it) and moving the energy to the light bulb (thereby heating it). It seems you could then use any old heat engine to extract work by letting the heat flow from the resulting hotter place back to the colder place, getting "limitless power" for free from your perpetual motion machine. Conceivably it's a sort of heat pump that gets some multiplier above the battery power. But I think the burden of proof is on the Arkansas folks to explain how this can be. If I had more energy (no pun intended, really) right now I'd try to find the paper that the press release is based on, to see if there's a little more truth there.

Meanwhile, I doubt it.

The abstract of the paper Fluctuation-induced current from freestanding graphene [1]:

> At room temperature, micron-sized sheets of freestanding graphene are in constant motion, even in the presence of an applied bias voltage. We quantify the out-of-plane movement by collecting the displacement current using a nearby small-area metal electrode and present an Ito-Langevin model for the motion coupled to a circuit containing diodes. Numerical simulations show that the system reaches thermal equilibrium and the average rates of heat and work provided by stochastic thermodynamics tend quickly to zero. However, there is power dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath. The exact power formula is similar to Nyquist's noise power formula, except that the rate of change of diode resistance significantly boosts the output power, and the movement of the graphene shifts the power spectrum to lower frequencies. We have calculated the equilibrium average of the power by asymptotic and numerical methods. Excellent agreement is found between experiment and theory.

[1] https://journals.aps.org/pre/abstract/10.1103/PhysRevE.102.0...

> “People may think that current flowing in a resistor causes it to heat up, but the Brownian current does not. In fact, if no current was flowing, the resistor would cool down,” Thibado explained. “What we did was reroute the current in the circuit and transform it into something useful.”

Based on this I understood that it'd indeed cool down and create a heat gradient if it wasn't doing any work, but the difference it'd create is instead used to induce a current, which means it probably wouldn't cool down as long as that potential is used in this way instead (?)

So it converts heat into work without a temperature gradient? That is the real revolution. I wonder if this could scale into a cooling solution for chips.

I think some minuscule amount of energy is taken from the thermal bath (the environment is considered a thermal bath - you can take heat from it and it's so big its temperature won't budge), converted into electricity and then back to heat in the load resistor. They all remain in the same temperature if I'm not gravely mistaken.