Tech Briefs Magazine - April 2023 - 9

Q & A
Nanogenerator Harnesses the
Renewable Energy of Open Ocean Waves
Zhiqun (Daniel) Deng
and a team of researchers
at the Pacific Northwest
National Laboratory
(PNNL) are working
to develop a nanogenerator
that harnesses
the renewable energy
of open ocean waves to
power observation platforms, and more,
in the middle of the ocean.
Tech Briefs: What got you started
on this project?
Dr. Zhiqun (Daniel) Deng: My research
focuses on developing integrated sensing
systems to understand and mitigate
the environmental impacts of renewable
energy systems. And part of developing
sensors deals with the question of how to
power them.
Instead of going right to a large utility-scale
system, our goal is to identify
immediate applications. That's why we
came up with a technique to power small
sensors as our first application.
What we have right now is very small
- milliwatts. But many acoustic sensors
can run on less than milliwatts.
Tech Briefs: Tell me a little bit about
the device.
Deng: We use the triboelectric nanogenerator
approach. Our device has two
main parts - an external cylinder and
an internal cylinder. Our innovation is
we have a pair of magnets. Our device
goes up along a wave, but the repellent
force between the two magnets holds
the relative position between the external
cylinder and the internal cylinder
so they don't move. Because of the added
mass on the internal cylinder, once
the device starts to rotate the potential
energy gets bigger and bigger, but
the repellent force of the two magnets
holds the rotor in place until it cannot
hold anymore as it starts to move past
the crest of the wave. Then the internal
cylinder will start to rotate very fast. If
Tech Briefs, April 2023
you didn't have the repellent magnets,
there would always be a slow rotation
during the whole cycle.
Although the rotor only moves during
a small fraction of the wave motion,
because of the quick sliding motion
between the internal and external cylinders,
it generates more electricity and
has higher efficiency.
Tech Briefs: Isn't the static electricity
generated by the triboelectric
nanogenerator at a high voltage?
Deng: That's a key challenge because
it's hundreds of volts, but at a very small
current. So, we have to use an efficient
power management circuit.
Tech Briefs: Would the power
management circuit be up on the
surface of the water?
HIGH-PRECISION
Deng: Ours is an integrated system
- all in one package. We're hoping
that eventually it can be integrated with
whatever the application platform is.
For example, if it is a big buoy, it can
be either external or inside the housing
of the system platform. That's why we
need to make all the parts as small as
possible so it can be more adaptable for
all of its applications.
Tech Briefs: Is there anything you
want to add?
Deng: We still have a long way to go.
We can power small sensors but our
goal is to increase our output to the
watts-level so we can power larger systems.
In the future, we would like to
develop our technology to be used as
a charging station for underwater vehicles
at the 100-Watts level to be placed
in the open ocean - that's a long-term
goal.
Finally, we hope to deploy our nanogenerator
system in the field in a couple
of years.
To read the full interview, visit www.
techbriefs.com.
www.techbriefs.com
Contact our application engineers:
Phone +1/919 787 9707
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Tech Briefs Magazine - April 2023

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