Generating energy from waste heat dissipated by electronic devices, appliances, and even car engines is widely seen as a largely untapped resource.
Now mechanical engineers at the University of Utah believe they’ve found a way to harness this energy with the creation of a silicon chip that can convert thermal radiation into electricity.
|University of Utah mechanical engineering associate professor Mathieu Francoeur has discovered a way to produce more electricity from heat than thought possible by creating a silicon chip that converts more thermal radiation into electricity. (Image source: Dan Hixson/University of Utah College of Engineering)
The work, led by Associate Professor Mathieu Francoeur, paves the way for computers, mobile devices, and other electronics with a much longer battery life because they can generate their own electricity, he said.
“You put the heat back into the system as electricity,” Francoeur said in a press statement. “Right now, we’re just dumping it into the atmosphere. It’s heating up your room, for example, and then you use your AC to cool your room, which wastes more energy.”
Indeed, researchers estimate that as much as two-thirds of energy consumed in the United States each year is emitted as waste heat, which leaves a large energy resource that current is not being utilized.
Pushing Past Limits
Key to Francoeur and his team’s work was to surpass a previously determined, so-called “blackbody limit” on how much energy could be produced from thermal radiation, or heat. Researchers solved this problem by developing technology on the nanoscale, he said.
“Nobody can emit more radiation than the blackbody limit,” Francoeur said in a press statement. “But when we go to the nanoscale, you can.”
Specifically, the team developed a device that uses two silicon surfaces very close together, producing a 5 millimeter-by-5 millimeter chip using two silicon wafers with a nanoscopic gap between them of 100 nanometers thick. The chip is about the size of the head of an eraser on a pencil, and the gap is about a thousandth the thickness of a human hair, researchers said.
Researchers put the chip in a vacuum and heated one surface while they cooled another surface, creating a heat flux that can generate electricity, they said.
While the concept itself is not unique to the research, what is new about the work is that the two silicon surfaces exist so close together at a microscopic scale without touching each other, researchers reported in paper on their work in the journal Nature Nanotechnology. The closer the surfaces are to each other, the more electricity they can generate, researchers said.
Francoeur envisions a number of uses for the chip the team developed. It could be used to help cool down portable devices like laptops and smartphones—which as any daily user of these devices knows, can overheat easily. Moreover, the chip can enable those devices to take waste heat and turn it into more battery life—up to as much as 50 percent more, researchers said.
Solar panels and medical devices also could benefit from using the chip, researchers said. In the former, efficiency could be improved by increasing the amount of electricity from the sun’s heat. The latter could use the chip as a sole source of energy in small, implantable devices, such as pacemakers, researchers said.
Even automobiles could run more efficiency using the device, which could draw heat from the engine to help power a car’s electrical systems, researchers reported. Computer processors also could benefit in a similar way, by drawing heat they dissipate away from the system and saving energy currently used on fans that cool processors.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.
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