Featured Research

from universities, journals, and other organizations

Improving materials that convert heat to electricity and vice-versa: Turning waste heat into electricity

Date:
May 5, 2013
Source:
University of Michigan
Summary:
Thermoelectric materials can be used to turn waste heat into electricity or to provide refrigeration without any liquid coolants, and new study has found a way to nearly double the efficiency of a particular class of them that's made with organic semiconductors.

"Eventually this technology could allow us to create a flexible sheet -- think of Saran Wrap -- that can be rolled out or wrapped around a hot object to generate electricity or provide cooling," one of the researchers said.
Credit: Coprid / Fotolia

Thermoelectric materials can be used to turn waste heat into electricity or to provide refrigeration without any liquid coolants, and a research team from the University of Michigan has found a way to nearly double the efficiency of a particular class of them that's made with organic semiconductors.

Organic semiconductors are carbon-rich compounds that are relatively cheap, abundant, lightweight and tough. But they haven't traditionally been considered candidate thermoelectric materials because they have been inefficient in carrying out the essential heat-to-electricity conversion process.

Today's most efficient thermoelectric materials are made of relatively rare inorganic semiconductors such as bismuth, tellurium and selenium that are expensive, brittle and often toxic. Still, they manage to convert heat into electricity more than four times as efficiently as the organic semiconductors created to date.

This greater efficiency is reflected in a metric known by researchers as the thermoelectric "figure of merit." This metric is approximately 1 near room temperature for state-of-the-art inorganic thermoelectric materials, but only 0.25 for organic semiconductors.

U-M researchers improved upon the state-of-the-art in organic semiconductors by nearly 70 percent, achieving a figure-of-merit of 0.42 in a compound known as PEDOT:PSS.

"That's about half as efficient as current inorganic semiconductors," said project leader Kevin Pipe, an associate professor of mechanical engineering as well as electrical engineering and computer science. Pipe is a co-author of a paper on the research published in Nature Materials on May 5, 2013.

PEDOT:PSS is a mixture of two polymers: the conjugated polymer PEDOT and the polyelectrolyte PSS. It has previously been used as a transparent electrode for devices such as organic LEDs and solar cells, as well as an antistatic agent for materials such as photographic films.

One of the ways scientists and engineers increase a material's capacity for conducting electricity is to add impurities to it in a process known as doping. When these added ingredients, called dopants, bond to the host material, they give it an electrical carrier. Each of these additional carriers enhances the material's electrical conductivity.

In PEDOT doped by PSS, however, only small fraction of the PSS molecules actually bond to the host PEDOT; the rest of the PSS molecules do not become ionized and are inactive. The researchers found that these excess PSS molecules dramatically inhibit both the electrical conductivity and thermoelectric performance of the material.

"The trouble is that the inactive PSS molecules push the PEDOT molecules further apart, making it harder for electrons to jump between PEDOT molecules," Pipe said. "While ionized PSS molecules improve electrical conductivity, non-ionized PSS molecules reduce it."

To improve its thermoelectric efficiency, the researchers restructured the material at the nanoscale. Pipe and his team figured out how to use certain solvents to remove some of these non-ionized PSS dopant molecules from the mixture, leading to large increases in both the electrical conductivity and the thermoelectric energy conversion efficiency.

This particular organic thermoelectric material would be effective at temperatures up to about 250 degrees Fahrenheit.

"Eventually this technology could allow us to create a flexible sheet -- think of Saran Wrap -- that can be rolled out or wrapped around a hot object to generate electricity or provide cooling," Pipe said.


Story Source:

The above story is based on materials provided by University of Michigan. Note: Materials may be edited for content and length.


Journal Reference:

  1. G-H. Kim, L. Shao, K. Zhang, K. P. Pipe. Engineered doping of organic semiconductors for enhanced thermoelectric efficiency. Nature Materials, 2013; DOI: 10.1038/nmat3635

Cite This Page:

University of Michigan. "Improving materials that convert heat to electricity and vice-versa: Turning waste heat into electricity." ScienceDaily. ScienceDaily, 5 May 2013. <www.sciencedaily.com/releases/2013/05/130505145941.htm>.
University of Michigan. (2013, May 5). Improving materials that convert heat to electricity and vice-versa: Turning waste heat into electricity. ScienceDaily. Retrieved April 18, 2014 from www.sciencedaily.com/releases/2013/05/130505145941.htm
University of Michigan. "Improving materials that convert heat to electricity and vice-versa: Turning waste heat into electricity." ScienceDaily. www.sciencedaily.com/releases/2013/05/130505145941.htm (accessed April 18, 2014).

Share This



More Matter & Energy News

Friday, April 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com
German Researchers Crack Samsung's Fingerprint Scanner

German Researchers Crack Samsung's Fingerprint Scanner

Newsy (Apr. 16, 2014) German researchers have used a fake fingerprint made from glue to bypass the fingerprint security system on Samsung's new Galaxy S5 smartphone. Video provided by Newsy
Powered by NewsLook.com
Porsche CEO Says Supercar Is Not Dead: Cue the Spyder 918

Porsche CEO Says Supercar Is Not Dead: Cue the Spyder 918

TheStreet (Apr. 16, 2014) The Porsche Spyder 918 proves that, in an automotive world obsessed with fuel efficiency, the supercar is not dead. Porsche North America CEO Detlev von Platen attributes the brand's consistent sales growth -- 21% in 2013 -- with an investment in new technology and expanded performance dynamics. The hybrid Spyder 918 has 887 horsepower and 944 lb-ft of torque, but it can run 18 miles on just an electric charge. The $845,000 vehicle is not a consumer-targeted vehicle but a brand statement. Video provided by TheStreet
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