Scientists are harnessing an unused energy source to power smart sensor networks

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UNIVERSITY PARK, Pennsylvania — 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 that can harvest this wasted magnetic field energy and convert it into enough electricity to power next-generation sensor networks for smart buildings and factories.

“Just as sunlight is a free source of energy that 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 pervasive energy present in our homes, offices, workspaces and cars. It’s everywhere, and we have the ability to harvest that background noise and convert it into usable electricity. »

A team led by Penn State scientists has developed a device that provides 400% more power output than other leading technologies when working with low-level magnetic fields, such as 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 many functions, you can actually improve energy efficiency in a very significant way,” Priya said. “Buildings are one of the biggest consumers of electricity in the United States. So even a few percent drop in power consumption could represent or translate into megawatts of savings. It’s the sensors that will automate those controls, and this technology is a realistic way to power those sensors.

Researchers have 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 electrical current, the scientists said.

When placed 4 inches from a radiator, the device produces enough electricity to power 180 rows of LEDs and at 8 inches, enough to power a digital alarm clock. The scientists reported the findings in the journal Energy and Environmental Science.

“These results provide significant advances toward sustainable power for embedded sensors and wireless communication systems,” said Min Gyu Kang, assistant research professor at Penn State and co-lead author of the study.

The scientists used a composite structure, superimposing two different materials. One of these materials is magnetostrictive, which converts a magnetic field into stress, and the other is piezoelectric, which converts stress, or vibration, into an electric field. The suit allows the device to transform 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 motion and contributes to higher electricity output, the scientists said.

“The beauty of this research is that it uses known materials, but designs the architecture to essentially maximize the conversion of the magnetic field into electricity,” Priya said. “This achieves high power density in low amplitude magnetic fields.”

Rammohan Sri Ramdas, an assistant research professor at Penn State, participated in the research.

Hyeon Lee and Prashant Kumar, research assistants at Virginia Tech, and Mohan Sanghadasa, senior researcher at the Aviation and Missile Center, US Army Combat Capabilities Development Command, also contributed.

Some of the team members in this study were funded by the Office of Naval Research and the others by the National Science Foundation.

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