Engineers Develop Highly Efficient Material That Converts Waste Heat Into Energy

A team of researchers from Northwestern University and Seoul National University has developed an extremely high-performing thermoelectric material in a practical form, and it may be the most efficient yet, according to a press release.  

After eliminating an oxidation issue that had reduced performance in previous tests, the researchers were able to obtain a high conversion rate, as described in the study published in the journal Nature Materials. This new material, purified tin selenide in polycrystalline form, possesses all the good stuff it needs to become a viable material for converting waste heat to electricity. 

How thermoelectric systems generate electricity

Thermoelectricity is a fascinating two-way mechanism that converts temperature variations to electric voltage and vice versa. While thermoelectric devices are used in some, like NASA's Perseverance rover on Mars, these applications are low in numbers.

These devices have not taken off like solar cells due to the substantial hurdles in producing good ones. "We are focusing on developing a material that would be low cost and high performance and propel thermoelectric devices into a more widespread application," says Mercouri Kanatzidis, corresponding author of the study who specializes in designing new materials.

To put it simply, thermoelectric systems generate electricity by utilizing a temperature gradient. When one side of a special material is heated, this can cause electrons to begin moving from the warmer side to the cooler side, resulting in the generation of an electric current. By utilizing this technology, scientists could one day help recycle energy that would otherwise be wasted as heat in electronics, power plants, and engines.

The new material  

In thermoelectrics, the efficiency of waste heat conversion is indicated by its “figure of merit,” a number known as ZT. The higher the number, the better the conversion rate, and in this recent study, the researchers claim to have achieved a record ZT of 3.1.

"This opens the door for new devices to be built from polycrystalline tin selenide pellets and their applications explored," Kanatzidis says.

For example, the thermoelectric material could find use in the automobile industry, where a substantial percentage of gasoline's potential energy goes out of the exhaust, or heavy manufacturing industries such as glass and brick making, refineries, coal- and gas-fired power plants.