Magnetics Business & Technology - July/August 2020 - 30

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Penn State Scientists Develop a New Mechanism to Harvest Stray Magnetic Fields

A team of scientists has developed a new mechanism to harvest stray magnetic fields all around us and convert the energy into useful, usable
electricity. Image: Kai Wang
The electricity that lights our homes and powers our appliances also
creates small magnetic fields that are present all around us. Scientists
have developed a new mechanism capable of harvesting this wasted
magnetic field energy and converting it into enough electricity to
power next-generation sensor networks for smart buildings and
factories.
"Just like sunlight is a free source of energy we try to harvest, so are
magnetic fields," said Shashank Priya, professor of materials science
and engineering and associate vice president for research at Penn
State. "We have this ubiquitous energy present in our homes, office
spaces, work spaces and cars. It's everywhere, and we have an opportunity to harvest this background noise and convert it to useable
electricity."
A team led by Penn State scientists developed a device that provides
400 percent higher power output compared to other state-of-the-art
technology when working with low-level magnetic fields, like those
found in our homes and buildings.
The technology has implications for the design of smart buildings,
which will require self-powered wireless sensor networks to do
things like monitor energy and operational patterns and remotely
control systems, the scientists said.
"In buildings, it's known that if you automate a lot of functions, you
could actually improve the energy efficiency very significantly," Priya
said. "Buildings are one of the largest consumers of electricity in the
United States. So even a few percent drop in energy consumption
could represent or translate into megawatts of savings. Sensors are
what will make it possible to automate these controls, and this technology is a realistic way to power those sensors."
Researchers designed paper-thin devices, about 1.5 inches long, that
can be placed on or near appliances, lights, or power cords where
the magnetic fields are strongest. These fields quickly dissipate away
from the source of flowing electric current, the scientists said.

to power a digital alarm clock. The scientists reported the findings in
the journal Energy and Environmental Science.
"These results provide significant advancements toward sustainable
power for integrated sensors and wireless communication systems,"
said Min Gyu Kang, an assistant research professor at Penn State and
co-lead author on the study.
The scientists used a composite structure, layering two different
materials together. One of these materials is magnetostrictive, which
converts a magnetic field into stress, and the other is piezoelectric,
which converts stress, or vibrations, into an electric field. The combination allows the device to turn a magnetic field into an electric
current.
The device has a beam-like structure with one end clamped and
the other free to vibrate in response to an applied magnetic field. A
magnet mounted at the free end of the beam amplifies the movement and contributes toward a higher production of electricity, the
scientists said.
"The beauty of this research is it uses known materials, but designs
the architecture for basically maximizing the conversion of the magnetic field into electricity," Priya said. "This allows for achieving high
power density under low amplitude magnetic fields."
Rammohan Sri Ramdas, an assistant research professor at Penn State,
participated in the research.
Also contributing were Hyeon Lee and Prashant Kumar, research
assistants at Virginia Tech, and Mohan Sanghadasa, senior research
scientist at the Aviation and Missile Center, U.S. Army Combat Capabilities Development Command.
Some of the team members in this study were funded through the
Office of Naval Research and the others through National Science
Foundation.

When placed 4 inches from a space heater, the device produced
enough electricity to power 180 LED arrays, and at 8 inches, enough

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