Smart sensor networks run on magnetic power

Smart sensor networks run on magnetic power
A team of scientists has developed a new mechanism to harvest stray magnetic fields and convert the energy into useful, usable electricity. (Kai Wang, Penn State University)

A research team led by Penn State University scientists has developed a new mechanism able to harvest wasted magnetic field energy and convert it into electricity to power next-generation sensor networks for smart buildings and factories.

According to an article on the university’s website, the device reportedly provides 400% higher power output compared to other state-of-the-art technology when working with low-level magnetic fields, such as found in homes and buildings. The scientists reported the findings in the journal Energy and Environmental Science.

"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."

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According to the scientists, 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 researchers designed paper-thin devices, about 1.5 in. 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.

When placed 4 in. from a space heater, the device produced enough electricity to power 180 LED arrays, and at 8 in., enough to power a digital alarm clock.

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 enables the device to turn a magnetic field into an electric current.

The device’s beam-like structure has 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."

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