Oct 15 2020

Power From Graphene

The headline reads, “Physicists build circuit that generates clean, limitless power from graphene.” There are some red flags there – my skeptical antenna always prick up when I see claims of limitless power. However, unlike the silly caricature of those who push back against appropriate skepticism, my doubts were the beginning of the process, not the end. I had many questions. How much power are we talking about? Where is the energy coming from (always a good question)? Does this require “free energy” or breaking any of the laws of thermodynamics? Is this theoretical or does it exist?

The press release, as is often the case, did not delve into these questions to a satisfactory degree, but was mainly hype. So I went to the original article –  Fluctuation-induced current from freestanding graphene. (Sorry, it’s behind a paywall, but I had access through my institution.) This helped, but was technically over my head in some parts. What I needed was to talk to an expert who could translate the technical bits for me. We discussed this news item, as much as we could, on the SGU and asked for help getting in touch with someone who could help unpack the physics at work here. Listener David Thompson, who is at the University of Arkansas where the research was done, was able to hook us up to the lead author of the study, Paul Thibado. We interviewed him yesterday for the show that will air this Saturday. Listen to the interview for all the details, but here is a quick breakdown.

The claim is that Thibado and his group have built a circuit that can harvest electrical energy from freestanding graphene. Graphene is a 2-dimensional material of carbon, think of a chickenwire with carbon atoms at each of the connection points. Graphene has interesting properties, and we are still near the beginning of exploring possible applications of this material. Freestanding graphene means the sheet is floating like a picture in a frame – this allows it to move freely. This sheet of graphene will undulate, buckle, and wave (like the surface of the ocean) due to background energy in a form a Brownian motion. The question Thibado and his group asked is this – can we harvest energy from the motion of the graphene, in the same way that you might harvest energy from the wind blowing or the sun shining? The answer, they found, is yes.

The analogy he gave is that if you imagine air molecules moving in completely random directions then it may seem impossible to harvest energy from that medium. But if the air molecules are moving in the same direction (without changing their total energy, i.e. their temperature) that creates a wind that can be used to harvest energy. So the trick was to create a circuit that could get energy from the movement of the graphene in the same way that a wind turbine gets energy from the wind. The solution was apparently to use two diodes in the circuit to create alternating current. This acted like a sort-of ratchet that would move energy in one direction.

The math here is still beyond me – in fact it was beyond Thibado. He built the circuit and collected data showing that it works, but could not get the results published because the journals wanted to see theoretically how it was working. They wanted to see the math. Let’s take a moment to consider this – a mainstream physicist built a circuit and collected years of data showing that it works, but the journals still wanted to see the theoretical mechanism of how it works before publishing the results. Take this into consideration the next time some free-energy guru whines that he cannot be taken seriously just because his claims break the laws of thermodynamics.

In any case – Thibado then collaborated with theoretical physicists who could do the math. It took them two years to sort it out. There is an interesting wrinkle here. Previously physicists believed that such Brownian motion could not be used as a source of energy. You could not harvest energy from Brownian motion. We asked Thibado about this and he pointed out that at the time physicists did not have the math and theory to address this question. The new field of stochastic thermodynamics was necessary to understand what is happening. With the math sorted, they were able to get the results published.

Where does the energy come from? It comes from environmental heat. While the circuit is producing current the environment cools a little. But also any energy applied to the graphene would increase its movement – vibration, sunlight, or heat. This can be important when we think of applications.

So what does all this mean? Is this just a curious physics phenomenon, or is there a practical application? In terms of how much energy it produces, the energy density is somewhere between wind turbines and solar panels, so it is on the same level as these sources of energy. But it is unlikely, form a practical point of view, that we will build massive circuits for grid energy. Rather, this technology is suited to tiny applications, embedding chips with these circuits into small electronic devices. This could replace batteries for such devices, and would provide indefinite energy because it is not storing energy, its harvesting it from the environment.

In the end, as far as I can tell, this research seems legitimate. Nothing is breaking the laws of thermodynamics. There is a known source of energy. The circuit has actually been built and tested, and the math all seems to work out. The only piece that remains, and this is a big piece, is translating this into practical applications. Working in the lab is one thing, but powering a device that people use out in the world is another. The goal is to build computer chips with millions of these tiny circuits on them. These in turn could directly power a device, or be hooked up to a capacitor or battery that it charges over time. But – how much will such a chip cost? Mass producing graphene of high quality at a reasonable cost is still a challenge. How robust would such a device be? Do they break down over time? Is this the kind of thing that NASA will be putting into deep space probes, or will every smart phone have one? Are we seeing the technology that will eventually make every small electronic device self-charging?

Also – what would the impact of such devices be on our energy infrastructure? Will the impact be significant, or tiny? What will the energy efficiency timeline be – in other words, how long would such a chip have to operate until it generates the same amount of energy as was used in its manufacture?

I’ll have to keep a close eye on this research. Thibado says the next step in his research, putting these circuits onto a chip, will be ready in about six months. We’ll see how that works out and where it goes from there.


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