Stray, ambient magnetic fields that are naturally created from electricity usage should be captured, diverted, and converted into power for Internet of Things sensors, researchers say.
“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, in a statement published on the university’s web site. “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.”
Electricity produces tiny magnetic fields around common power cables, computers and lighting found in factories, homes and offices. That energy, if harnessed, could power sensors and small data-sending radios, the academics think. Penn State is attempting to design ambient power receptors for IoT.
The group at Penn State has been having some success getting it to work. Experimental devices that are thin and about 1.5 inches long are being tested. Placing the capture-device around or on common appliances does produce electricity, the researchers claim. The key is to put the device where the magnetic field is the strongest. In one experiment, the researchers were able to generate enough power to run 180 LED lighting arrays with a device placed about 4 inches from a space heater. At 8 inches, the device produced enough electricity to operate a clock.
“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 joint lead author of the study.
Electricity and magnetism have always gone hand in hand. Magnetism is created by a moving electric charge. It’s that movement which creates the magnetic field. That’s why low-level magnetism is manifested in electrical wires generally, for example—the electricity is moving along the cable.
In this case, the scientists are converting the magnetic field, which is caused by the moving electricity, into a separate electrical current. They’re doing it with materials science by combining two materials. One of the materials is a magnetostrictor – it converts the magnetic field into stress-generating vibrations. The another material is piezoelectric, which grabs the vibrations and translates that energy into electricity.
How to power sensors
Producing usable power from stray magnetic fields is just one stab at powering the IoT. Just how one goes about producing power for the millions, and possibly billions, of environmental, factory process and other sensors that are expected to come on stream as IoT takes off is up for grabs.
Batteries have limitations—they need to be changed or charged, for example. Ambient humidity is one possibility I wrote about recently. In that case, bio-electronics have been proven to capture half-a-volt from ambient air, scientists claim. That’s enough to operate rudimentary sensors. Waste heat, too, is another possible source: Researchers are exploring ways to convert excess heat, such as is found in data centers, into light, and then turn that light into electricity.
Other angles include simply reducing energy consumption through more efficient chips or streamlined wireless communications hardware. Other parasitic techniques are being tried. They include turning existing wireless noise into a data carrier. It’s efficient because one doesn’t have to make so much power for radio transceivers—the carrier already exists.
In the case of the Penn State work, less obvious benefits might exist, too.
“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.”
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