New way to turn waste heat into power could make cars, factories more efficient

WASHINGTON - Cashing on quantum physics, University of Arizona physicists have discovered a new way of harvesting waste heat and turning it into electrical power-a feat that holds promise for making cars, power plants, factories and solar panels more efficient.

Using a theoretical model of a so-called molecular thermoelectric device, the technology holds great promise for making cars, power plants, factories and solar panels more efficient, to name a few possible applications.

In addition, more efficient thermoelectric materials would make ozone-depleting chlorofluorocarbons, or CFCs, obsolete.

The research group led by Charles Stafford, associate professor of physics, published its findings in the September issue of the scientific journal, ACS Nano.

“Thermoelectricity makes it possible to cleanly convert heat directly into electrical energy in a device with no moving parts,” said lead author Justin Bergfield, a doctoral candidate in the UA College of Optical Sciences.

“Our colleagues in the field tell us they are pretty confident that the devices we have designed on the computer can be built with the characteristics that we see in our simulations.”

“We anticipate the thermoelectric voltage using our design to be about 100 times larger than what others have achieved in the lab,” Stafford added.

Unlike existing heat-conversion devices such as refrigerators and steam turbines, the devices of Bergfield and Stafford require no mechanics and no ozone-depleting chemicals.

Instead, a rubber-like polymer sandwiched between two metals acting as electrodes can do the trick.

Car or factory exhaust pipes could be coated with the material, less than 1 millionth of an inch thick, to harvest energy otherwise lost as heat and generate electricity.

The physicists take advantage of the laws of quantum physics, a realm not typically tapped into when engineering power-generating technology.

The key to the technology lies in a quantum law physicists call wave-particle duality-tiny objects such as electrons can behave either as a wave or as a particle.

The researchers discovered the potential for converting heat into electricity when they studied polyphenyl ethers, molecules that spontaneously aggregate into polymers, long chains of repeating units.

“We had both worked with these molecules before and thought about using them for a thermoelectric device, but we hadn’t really found anything special about them until Michelle Solis, an undergrad who worked on independent study in the lab, discovered that, low and behold, these things had a special feature,” said Bergfield,

Using computer simulations, Bergfield then “grew” a forest of molecules sandwiched between two electrodes and exposed the array to a simulated heat source.

“As you increase the number of benzene rings in each molecule, you increase the power generated,” said Bergfield.

The secret to the molecules’ capability to turn heat into power lies in their structure-like water reaching a fork in a river, the flow of electrons along the molecule is split in two once it encounters a benzene ring, with one flow of electrons following along each arm of the ring.

“We are the first to harness the wave nature of the electron and develop a concept to turn it into usable energy,” said Stafford. (ANI)