Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Scientists discover better way to generate power from thermal sources


Your car’s engine loses 70 percent of its energy as waste heat -- but Australian and Oregon scientists may have figured out an efficient way not only to recover that lost energy, but to at long last capture the power-producing potential of geothermal heat.

The trick is to convert it to electricity -- and a promising way to accomplish this, the researchers have discovered, involves using extremely thin nanowires to potentially more than double the efficiency of thermoelectric materials. "If all goes well, nanostructured thermoelectric devices may be practical for applications such as recycling of waste heat in car engines, on-chip cooling of computer microprocessors and silent, more compact domestic refrigerators," says Heiner Linke, a University of Oregon assistant professor of physics associated with ONAMI, the Oregon Nanoscience and Microtechnologies Institute.

Linke and Tammy Humphrey, an Australian Research Council fellow currently visiting the University of California at Santa Cruz, presented their findings today (Tuesday, April 5) at the Nanoscale Devices and System Integration Conference in Houston. A review of their study in the online version of the journal Nature Materials described their results as "dramatic" and "a phenomenal enhancement relative to current bulk thermoelectrics."

The pair discovered that two objects can have different temperatures yet still be in equilibrium with each other at the nanoscale-a fact that may blow right past a non-physicist but which is crucial in order to attain the kind of performance needed for widespread application of thermoelectric technology in power generation and refrigeration.

Imagine a hot cup of coffee sitting on a bench. The coffee will quickly cool because molecules in the cup spontaneously ferry heat from hot to cold in a rush to reach equilibrium with the temperature of the bench. The same effect happens with electrons in the materials studied by Humphrey and Linke. In physics, this is the law of thermodynamics: that heat will always flow from hot to cold. Of course, the energy expended by those electrons is normally lost.

Thermoelectric materials try to recover this energy by converting it to electricity, but they don’t work very well if the flow of heat is uncontrolled. The breakthrough presented by Humphrey and Linke involves controlling the motion of electrons using materials that are structured on the nanoscale. "The idea is to play one type of non-equilibrium (the temperature difference) against another one," Linke explains.

Humphrey and Linke have shown that if an electrical voltage is applied to an electrical system in addition to a temperature difference, it is possible to harness electrons having a specific energy. This means that if a nanostructured material is designed to only allow electrons with this particular energy to flow, a novel type of equilibrium is achieved in which electrons do not spontaneously ferry heat from hot to cold.

"This delicate balance may have huge practical importance because it means that thermoelectric devices, which use electrical contact between hot and cold regions in a semiconductor to transform heat into useful electrical energy, can be operated near equilibrium," says Humphrey. "This is a key requirement for cranking up their efficiency toward the Carnot limit, the maximum efficiency possible for any heat engine."

Because the system is in a state of equilibrium, the flow of electrons is reversible, Humphrey explains, noting that reversibility allows the device to reach maximum possible efficiency.

Until now, the efficiency of such devices, which have no moving parts and can be small enough to fit on a microchip, has been too low (less than 15 percent of the Carnot limit for power generation) for use in all but a few specialized applications.

However, Linke and Humphrey say implementation of their design principle is possible by tailoring the electronic bandstructure in state-of-the-art thermoelectric materials made up of a huge number of nanowires. If all goes well, nanostructured thermoelectric devices with efficiencies close to 50 percent of the Carnot limit may be realized, Linke says.

Such materials could make possible the generation of electricity from geothermal sources -- or from the waste heat of engines in hybrid cars, he explains.

Melody Ward Leslie | EurekAlert!
Further information:

More articles from Power and Electrical Engineering:

nachricht Fluorescent holography: Upending the world of biological imaging
25.10.2016 | Colorado State University

nachricht Did you know that infrared heating is an essential part of automotive manufacture?
25.10.2016 | Heraeus Noblelight GmbH

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

3-D-printed structures shrink when heated

26.10.2016 | Materials Sciences

Indian roadside refuse fires produce toxic rainbow

26.10.2016 | Health and Medicine

First results of NSTX-U research operations

26.10.2016 | Physics and Astronomy

More VideoLinks >>>