Graphene can be a Great Way to Generate Power
Nature continues to surprise the scientific community by unfolding the shocking phenomenons that have the potential to significantly contribute to the advancement of mankind.
Nanotechnology is one such field where the discoveries lead to promising applications in sectors such as engineering, construction, space, energy, etc.
Graphene, a gift of nanotechnology, is one of the most important nanomaterials developed so far.
A group of scientists from the University of Arkansas has discovered an extraordinary phenomenon arising from a sheet of graphene. The team has been successful in developing a circuit that can capture thermal motion in graphene and turn it into electricity.
The profoundness of this discovery can be known from the fact that this way of generating energy contradicts the assertion of a well-known physicist Richard Feynman’s that the thermal motion of atoms, also called Brownian motion, cannot perform any work.
Before proceeding further, first, let’s understand what Graphene truly is.
What is Graphene?
Graphene is a single atom thick layer of carbon arranged in a 2-dimensional honeycomb lattice as seen in the image below.
Each atom in a graphene sheet is linked to its three closest neighbors by a σ-bond and contributes one electron to a conduction band that extends over the entire sheet. These conduction bands make it a semimetal with unusual properties.
It has excellent thermal & electrical conductivity along its plane and is about 100 times stronger than the strongest steel of the same thickness.
As a freestanding monolayer, Graphene alternately creates concave and convex ripples instead of remaining flat. The curvature in these ripples is inverted spontaneously in response to the ambient temperature.
Flipping of these ripples from concave to convex causes the movement of more than 10,000 atoms in the same direction, resulting in an extremely large force. This collective thermal motion has been converted into a stored electrical charge using a variable-capacitance machine.
How does it Harvest Energy?
This single atom thick layer (graphene) bends and ripples at room temperature without any external power source to cause this movement. Thus the graphene can generate its own power harnessing the Brownian motion. It is a source of renewable energy that never exhausts and also available at every moment. It can therefore be called a free energy device.
The research group accomplished this by constructing their circuit with two diodes for converting Alternating Current (AC) into a Direct Current (DC).
Placing the diodes in opposition permits the current to flow both ways, providing separate paths through the circuit and creating a pulsating DC that performs work on a load resistor.
What is even more astounding is that the on-off, switch-like behavior of the diodes amplifies the power delivered, rather than decreasing it, according to Professor Paul Thibado, who is also the leader of this research.
The rate of change in the resistance provided by the diodes contributes an extra factor to power.
The following images in sequence describe the working of the device.
The point worth noting is that the system (graphene and circuit) are at the same temperature, though the thermal environment is performing work on the load resistor. Thus there is no flow of heat between the two, and hence the second law of thermodynamics is not violated. A difference in temperature between the circuit & graphene in a power-generating circuit would be a clear contradiction to the second law of thermodynamics.
- The circuit induces a low-frequency current due to the relatively slow motion of graphene. This is beneficial from a technological viewpoint because electronics function more efficiently at lower frequencies. Hence this energy harvesting circuit based on graphene could be used to provide unlimited & clean low-voltage power to small devices or sensors.
- It could also serve as a low power replacement of a battery if the DC produced can be stored in a capacitor.
To Wrap Up
Even before the technology matures for use in commercial products, it could be rewarding for entrepreneurs if they successfully uncover business ideas that can immediately be validated & implemented using the current state of technology.
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