Back in the 1960’s, scientists were convinced that harvesting usable energy from the random movement of tiny particles was a dead end. Luckily, some people did not get the memo. These particles were just waiting for the right material to come along, and a graphene energy harvester from the University of Arkansas is putting them to work.
Putting Brownian Motion To Work
Before we get to Arkansas, let’s stop off at Brown University in Rhode Island for a quick primer on — you guessed it — Brownian motion, which is the key to the whole thing.
Back in 2016, researchers from Brown University and the Lawrence Berkeley National Laboratory recapped the state of Brownian motion science. They noted that the phenomenon was first described in 1827 by the botanist Robert Brown, when he observed “the incessant and irregular motion of small grains suspended in a fluid” under a microscope.
“In the classical sense, the phenomenon refers to the random movement of a particle in a medium, e.g., dust in a fluid,” the researchers explain, “However today, its theory can be also applied to describe the fluctuating behavior of a general system interacting with the surroundings, e.g., stock prices.”
The stock market is just the tip of the Brownian iceberg. The researchers list many other areas of application including: the microrheology of viscoelastic materials, artificial Brownian motors and self-propelling of active matter, fluctuation theorems for states far from equilibrium, and quantum fluctuations. Microrheology refers to a system for measuring the flow of matter, by the way.
The Beginnings Of A Graphene Energy Harvester
That’s a lot of useful activity around Brownian motion, considering that just a couple of generations ago such work was not particularly encouraged.
“Obtaining useful work from random fluctuations in a system at thermal equilibrium has long been considered impossible,” the University of Arkansas explained in a press release last August. A series of lectures in the 1960’s by an influential US physicist effectively shut down further discussion of Brownian energy harvesters for a period of time.
That time has come and gone for a number of reasons, one of them being the discovery of graphene in 2004. Graphene is a two-dimensional material that you can DIY yourself by pressing a piece of tape onto a chunk of graphite. Lift off the tape, and there’s your graphene.
The problem, of course, is getting it off the tape and onto something else. That’s not much of a problem any more because the discovery of graphene sparked a torrent of research papers tackling just that problem.
That brings us up to the new graphene energy harvester from the University of Arkansas. A research team based at the school has been studying the rippling motion of freestanding sheets of graphene for more than 10 years or so. They reached a milestone last August, when they published a new study titled, “Charging capacitors from thermal fluctuations using diodes” in the journal Physical Review E.
If you caught that thing about thermal fluctuations, that’s the key. The team observed that graphene sheets flip up and down in a rippling motion under ambient temperatures, and they presented a pathway for putting those flips to work.
The Road From Ripple To Work
The research team is headed up by Professor Paul Thibado of the school’s Department of Physics, and they have already gotten a head start.
Last summer the University of Arkansas took note of the team’s work on GEH (graphene energy harvester) technology. Here’s the explainer from the school (break added for readability):
“GEH uses a negatively charged sheet of graphene suspended between two metal electrodes. When the graphene flips up, it induces a positive charge in the top electrode. When it flips down, it positively charges the bottom electrode, creating an alternating current.
“With diodes wired in opposition, allowing the current to flow both ways, separate paths are provided through the circuit, producing a pulsing DC current that performs work on a load resistor.”
Apparently word got around, because last week the research team received a five-year grant of $904,000 from the WoodNext foundation to continue developing their graphene energy harvester.
From Nanowatts To Kilowatts?
The research is focusing on sensor-scale applications, not on creating new graphene solar cells or wind turbines. However, GEH’s could have a ripple effect on the entire renewable energy industry, so to speak, by opening up new opportunities to apply remote sensing.
Unlike battery-powered sensors, a GEH would extract energy from the local environment, potentially lasting for several decades before needing replacement.
Remote sensing can play a role in maximizing the efficiency of wind turbines, for example, as well as addressing potential maintenance problems before they become actual problems. Recent concerns over security at offshore wind farms in Europe also underscore the need for more accurate, long-lasting sensors.
Other climate-related uses cited by Thibado include logistic fleet management, livestock tracking, soil sensors, agricultural climate monitoring, manufacturing process monitoring, smart grids, and waste management among many others.
For now, though, the next goalpost for the U of A team is to boost the power output of their device, with an assist from the WoodNext Foundation grant.
“We have successfully developed a process for building graphene energy harvesting device structures,” Professor Thibado said in a press statement last week, “But current structures do not harvest enough power. This proposal will allow us to optimize these structures to harvest nanowatts of power, which is enough energy to run sensors.”
They will have plenty of work to do over the next five years. The terms of the WoodNext grant stipulate that the device must be capable of harvesting energy from different sources in their local environment: solar, thermal, acoustic, kinetic, nonlinear and ambient radiation.
Wait, What Is WoodNext?
If the WoodNext Foundation doesn’t ring any bells, join the club. The Texas-based philanthropy was created just a few years ago in 2021 by Roku CEO and founder Anthony Wood with his wife, Susan. They have been rather busy since then, with scores of grants for projects that “advance human progress and remove obstacles to a fulfilling life.”
“Because of the Woods’ strong ties to Texas, WoodNext’s geographic priority is the southern region of the United States, though the WoodNext Foundation also makes grants in other regions nationally and internationally,” the foundation explains.
Oh, Texas, again! Texas has been front and center in the transition to clean power despite pushback from its current political leadership, so it’s no surprise to see a Texas-based philanthropy helping to stir the clean power pot. Back in 2022, for example, WoodNext provided the National Renewable Energy Laboratory with financial support to encourage innovation in the fields of wave energy and solar-powered water desalination.
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Image (screenshot): Schematic of a graphene energy harvester designed to scavenge power from the local environment, courtesy of the University of Arkansas via YouTube.