Wednesday, June 27, 2012

Ancient Effect Harnessed To Produce Electricity From Waste Heat

The latest episode in the American Chemical Society's (ACS') award-winning Global Challenges/Chemistry Solutions podcast series describes the first-of-its-kind "pyroelectric nanogenerator," a new device designed to harvest the enormous amounts of energy wasted as heat every year to produce electricity.

A phenomenon first observed by an ancient Greek philosopher 2,300 years ago has become the basis
for a new device designed to harvest the enormous amounts of energy wasted as heat each year to
produce electricity. The first-of-its-kind “pyroelectric nanogenerator” is the topic of a report in
ACS’ journal Nano Letters.  Listen to Podcast

Based on a report by Zhong Lin Wang, Ph.D., and colleagues in the ACS journal Nano Letters, the new podcast is available without charge at iTunes and from www.acs.org/globalchallenges.

Credit: iStock

In the report, Wang and colleagues explain that more than 50 percent of the energy generated in the U.S. every year goes to waste, much of it as heat released to the environment by everything from computers to cars to long-distance electric transmission lines. Heat can be converted to electricity using something called the pyroelectric effect, first described by the Greek philosopher Theophrastus in 314 B.C., when he noticed that the gemstone tourmaline produced static electricity and attracted bits of straw when heated. Heating and cooling rearrange the molecular structure of certain materials, including tourmaline, and create an imbalance of electrons that generates an electric current. Wang's group wanted to apply the ancient principle to make a nanogenerator (NG), which uses a time-dependent temperature change to generate electricity and could take advantage of heat changes in the modern world.

To do that, the researchers made nanowires out of zinc oxide, a compound added to paints, plastics, electronics and even food. Using an array of short lengths of nanowire standing on end, they demonstrated a device that produces electricity when heated or cooled. They suggest the NGs could even produce power as temperatures fluctuate from day to night. "This new type of NG can be the basis for self-powered nanotechnology that harvests thermal energy from the time-dependent temperature fluctuation in our environment for applications such as wireless sensors, temperature imaging, medical diagnostics and personal microelectronics," the researchers said.

Heating and cooling rearrange the electronic structure of certain materials, including tourmaline, and create an imbalance of electrons that generates an electric current. Wang’s group wanted to apply the ancient principle to make a nanogenerator that could take advantage of heat changes in the modern world, which uses a time-dependent temperature change to generate electricity. He explains:

“We made nanowires out of zinc oxide, a compound added to paints, plastics, electronics and even food. Using an array of short lengths of nanowire standing on end, we demonstrated a device that produces electricity when heated or cooled.”

He suggests that the nanogenerators could even produce power as temperatures fluctuate from day to night.

“This new type of nanogenerator can be the basis for self-powered nanotechnology that harvests thermal energy from the time-dependent temperature fluctuation in our environment for applications such as wireless sensors, temperature imaging, medical diagnostics and personal microelectronics.”

Contacts and sources:
Michael Bernstein
American Chemical Society

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