Featured Research

from universities, journals, and other organizations

Surprising material could play huge role in saving energy: Tin selenide is best at converting waste heat to electricity

Date:
April 17, 2014
Source:
Northwestern University
Summary:
One strategy for addressing the world's energy crisis is to stop wasting so much energy when producing and using it, such as in coal-fired power plants or transportation. Nearly two-thirds of energy input is lost as waste heat. Now scientists have discovered a surprising material that is the best in the world at converting waste heat to useful electricity. This outstanding property could be exploited in solid-state thermoelectric devices, with potentially enormous energy savings.

Potential areas of application for the high-temperature thermoelectric material include the automobile industry (a significant amount of gasoline's potential energy goes out of a vehicle's tailpipe), heavy manufacturing industries (such as glass and brick making, refineries, coal- and gas-fired power plants) and places where large combustion engines operate continuously (such as in large ships and tankers).
Credit: Dmytro Panchenko / Fotolia

One strategy for addressing the world's energy crisis is to stop wasting so much energy when producing and using it, which can happen in coal-fired power plants or transportation. Nearly two-thirds of energy input is lost as waste heat.

Now Northwestern University scientists have discovered a surprising material that is the best in the world at converting waste heat to useful electricity. This outstanding property could be exploited in solid-state thermoelectric devices in a variety of industries, with potentially enormous energy savings.

An interdisciplinary team led by inorganic chemist Mercouri G. Kanatzidis found the crystal form of the chemical compound tin selenide conducts heat so poorly through its lattice structure that it is the most efficient thermoelectric material known. Unlike most thermoelectric materials, tin selenide has a simple structure, much like that of an accordion, which provides the key to its exceptional properties.

The efficiency of waste heat conversion in thermoelectrics is reflected by its figure of merit, called ZT. Tin selenide exhibits a ZT of 2.6, the highest reported to date at around 650 degrees Celsius. The material's extremely low thermal conductivity boosts the ZT to this high level, while still retaining good electrical conductivity.

The ZT metric represents a ratio of electrical conductivity and thermoelectric power in the numerator (which needs to be high) and thermal conductivity in the denominator (which needs to be low).

Potential areas of application for the high-temperature thermoelectric material include the automobile industry (a significant amount of gasoline's potential energy goes out of a vehicle's tailpipe), heavy manufacturing industries (such as glass and brick making, refineries, coal- and gas-fired power plants) and places where large combustion engines operate continuously (such as in large ships and tankers).

"A good thermoelectric material is a business proposition -- as much commercial as it is scientific," said Vinayak P. Dravid, a senior researcher on the team. "You don't have to convert much of the world's wasted energy into useful energy to make a material very exciting. We need a portfolio of solutions to the energy problem, and thermoelectric materials can play an important role."

Dravid is the Abraham Harris Professor of Materials Science and Engineering at the McCormick School of Engineering and Applied Science.

Details of tin selenide, probably among the world's least thermally conductive crystalline materials, are published today (April 17) by the journal Nature.

The discovery comes less than two years after the same research group broke the world record with another thermoelectric material they developed in the lab with a ZT of 2.2.

"The inefficiency of current thermoelectric materials has limited their commercial use," said Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences. "We expect a tin selenide system implemented in thermoelectric devices to be more efficient than other systems in converting waste heat to useful electricity."

The material, despite having a very simple structure, conducts heat so poorly that even moderate thermoelectric power and electrical conductivity are enough to provide high thermoelectric performance at high temperature.

The researchers did not expect to find tin selenide to be such a good thermoelectric material.

"Lidong Zhao, the first author of the paper, deserves a lot of credit for looking at tin selenide," said Kanatzidis, who also holds a joint appointment at Argonne National Laboratory. "He is a good example of the curious people we try to attract to Northwestern."

Zhao, a postdoctoral fellow in Kanatzidis' research group, grew crystals of tin selenide and measured the crystal in three directions, along each axis. He found that the thermal conductivity was "ridiculously low" along the a-axis but also along the other two axes.

"The results are eye-opening because they point in a direction others would not look," Dravid said. "This material has the potential to be applied to other areas, such as thermal barrier coatings."

Kanatzidis and Zhao identified the potential of the material intuitively by looking at its crystal structure. They confirmed its exceptional thermoelectric properties and then turned to Dravid and Christopher M. Wolverton to uncover how the crystal was behaving and why.

"We found that the bonds between some atoms in this compound are very weak and lead to exceptionally soft, floppy atomic vibrations," said Wolverton, a senior author of the paper and a professor of materials science at the McCormick School.

Wolverton, an expert in computational materials science related to energy applications, showed that the accordion-like structure and weak bonds lead to atoms that vibrate very slowly.

"These very weak vibrations are responsible for the inability of the material to conduct heat," Wolverton said. "Our theory provides the scientific basis as to why the material behaves the way it does and also provides us with a new direction to search for even higher-efficiency materials."

"Tin selenide reminds us of that popular TV commercial for a memory foam mattress in which a person can jump on one side of the mattress while a glass of wine a few feet away is unperturbed -- the vibrations do not reach the glass because of the mattress' material," Kanatzidis said.

"Similarly, in tin selenide, heat cannot travel well through this material because its soft, accordion-like structure doesn't transmit vibrations well," he said. "One side of tin selenide gets hot -- where the waste heat is, for example -- while the other side remains cool. This enables the hot side to generate useful electricity."

"Our discovery underscores why the Department of Energy EFRC program works," Kanatzidis said. "A multidisciplinary team, such as ours, can look at a problem from many different angles, with sustained funding increasing the chances of a scientific breakthrough. And we have a special ambience here -- the spirit of Northwestern is interdisciplinary."


Story Source:

The above story is based on materials provided by Northwestern University. The original article was written by Megan Fellman. Note: Materials may be edited for content and length.


Journal Reference:

  1. Li-Dong Zhao, Shih-Han Lo, Yongsheng Zhang, Hui Sun, Gangjian Tan, Ctirad Uher, C. Wolverton, Vinayak P. Dravid, Mercouri G. Kanatzidis. Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals. Nature, 2014; 508 (7496): 373 DOI: 10.1038/nature13184

Cite This Page:

Northwestern University. "Surprising material could play huge role in saving energy: Tin selenide is best at converting waste heat to electricity." ScienceDaily. ScienceDaily, 17 April 2014. <www.sciencedaily.com/releases/2014/04/140417124519.htm>.
Northwestern University. (2014, April 17). Surprising material could play huge role in saving energy: Tin selenide is best at converting waste heat to electricity. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2014/04/140417124519.htm
Northwestern University. "Surprising material could play huge role in saving energy: Tin selenide is best at converting waste heat to electricity." ScienceDaily. www.sciencedaily.com/releases/2014/04/140417124519.htm (accessed July 24, 2014).

Share This




More Earth & Climate News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Creative Makeovers for Ugly Cellphone Towers

Creative Makeovers for Ugly Cellphone Towers

AP (July 24, 2014) Mobile phone companies and communities across the country are going to new lengths to disguise those unsightly cellphone towers. From a church bell tower to a flagpole, even a pencil, some towers are trying to make a point. (July 24) Video provided by AP
Powered by NewsLook.com
Observation Boat to Protect Cetaceans During Ship Transfer

Observation Boat to Protect Cetaceans During Ship Transfer

AFP (July 22, 2014) As part of the 14-ship convoy that will accompany the Costa Concordia from the port of Giglio to the port of Genoa, there will be a boat carrying experts to look out for dolphins and whales from crossing the path of the Concordia. Duration: 01:02 Video provided by AFP
Powered by NewsLook.com
New Orleans Plans to Recycle Cigarette Butts

New Orleans Plans to Recycle Cigarette Butts

AP (July 21, 2014) New Orleans is the first U.S. city to participate in a large-scale recycling effort for cigarette butts. The city is rolling out dozens of containers for smokers to use when they discard their butts. (July 21) Video provided by AP
Powered by NewsLook.com
Shark Sightings a Big Catch for Cape Tourism

Shark Sightings a Big Catch for Cape Tourism

AP (July 21, 2014) A rise in shark sightings along the shores of Chatham, Massachusetts is driving a surge of eager vacationers to the beach town looking to catch a glimpse of a great white. (July 21) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins