Discovery offers new possibilities for clean energy research

May 06, 2014

University of Houston physicists have discovered a new thermoelectric material offering high performance at temperatures ranging from room temperature up to 300 degrees Celsius, or about 573 degrees Fahrenheit.

"This new material is better than the traditional material, Bismuth telluride, and can be used for waste heat conversion into electricity much more efficiently," said Zhifeng Ren, M.D. Anderson Chair professor of physics at UH and the lead author of a paper describing the discovery, published online by Nano Energy.

Ren, who is also principal investigator at the Texas Center for Superconductivity at UH, said the work could be important for clean energy research and commercialization at temperatures of about 300 degrees Celsius.

Bismuth telluride has been the standard thermoelectric material since the 1950s and is used primarily for cooling, although it can also be used at temperatures up to 250 C, or 482 F, for power generation, with limited efficiency.

For this discovery, Ren and other members of his lab used a combination of magnesium, silver and antimony to generate electricity from heat using the thermoelectric principle. They added a small amount of nickel, after which Ren said the compound worked even better.

The work was done in collaboration with researchers from the UH Department of Chemistry and the Massachusetts Institute of Technology. Huaizhou Zhao and Jiehe Sui, a member of Ren's lab whose home institute is the Harbin Institute of Technology in China, were primary contributors; Zhao is now a research scientist at the Institute of Physics with the Chinese Academy of Sciences.

The material works well up to 300 C, Ren said; work to improve its efficiency is ongoing.

The potential for capturing heat - from power plants, industrial smokestacks and even vehicle tailpipes - and converting it into electricity is huge, allowing heat that is currently wasted to be used to generate power. Ren said temperatures there can range from 200 C to 1,000 C, and until now, there hasn't been a thermoelectric material capable of working once conditions get beyond the lower levels of heat. Much of the demand ranges from 250 C to 300 C, he said.

Ren long has worked in thermoelectrics, among other scientific fields. His research group published an article in the journal Science in 2008 establishing that the efficiency - the technical term is the "figure of merit" - of Bismuth telluride could be increased as much as 20 percent by changing how it is processed. At the time, Ren was at Boston College.

And his lab last summer published a paper in the Proceedings of the National Academy of Sciences establishing tin telluride with the addition of the chemical element indium as a material capable of converting waste heat to electricity. But tin telluride works best at temperatures higher than about 300 C, or about 573 F, making it important to continue looking for another material that works at lower temperatures.

Ren's group isn't the first to study the new material, which has not been named but is referred to in the Nano Energy paper as simply MgAgSb-based materials, using the chemical names for the elements used to create it. The paper cites work done in 2012 by M.J. Kirkham, et al; that work used magnesium, silver and antimony in equal parts, Ren said, but resulted in impurities and poor conducting properties.

He said his lab found that using slightly less silver and antimony, and mixing the elements separately - putting magnesium and silver first in the ball milling process, adding the antimony after several hours - eliminated the impurities and significantly improved the thermoelectric properties.

"We had much different qualities," he said. "Better, with no impurities, and smaller grain size, along with much better thermoelectric properties."

University of Houston

Related Electricity Articles from Brightsurf:

Mirror-like photovoltaics get more electricity out of heat
New heat-harnessing 'solar' cells that reflect 99% of the energy they can't convert to electricity could help bring down the price of storing renewable energy as heat, as well as harvesting waste heat from exhaust pipes and chimneys.

Engineers use electricity to clean up toxic water
Powerful electrochemical process destroys water contaminants, such as pesticides. Wastewater is a significant environment issue.

Considering health when switching to cleaner electricity
Power plants that burn coal and other fossil fuels emit not only planet-warming carbon dioxide, but also pollutants linked to breathing problems and premature death.

Windows will soon generate electricity, following solar cell breakthrough
Semi-transparent solar cells that can be incorporated into window glass are a 'game-changer' that could transform architecture, urban planning and electricity generation, Australian scientists say in a paper in Nano Energy.

Static electricity as strong as lightening can be saved in a battery
Prof. Dong Sung Kim and his joint research team presented a new technology that can increase the amount of power generated by a triboelectric nanogenerator.

To make amino acids, just add electricity
By finding the right combination of abundantly available starting materials and catalyst, Kyushu University researchers were able to synthesize amino acids with high efficiency through a reaction driven by electricity.

Using renewable electricity for industrial hydrogenation reactions
The University of Pittsburgh's James McKone's research on using renewable electricity for industrial hydrogenation reactions is featured in the Journal of Materials Chemistry A's Emerging Investigators special issue.

Water + air + electricity = hydrogen peroxide
A reactor developed by Rice University engineers produces pure hydrogen peroxide solutions from water, air and energy.

Producing electricity at estuaries using light and osmosis
Researchers at EPFL are working on a technology to exploit osmotic energy -- a source of power that's naturally available at estuaries, where fresh water comes into contact with seawater.

Experimental device generates electricity from the coldness of the universe
A drawback of solar panels is that they require sunlight to generate electricity.

Read More: Electricity News and Electricity Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to