Researchers reported this week in the Proceedings of the National Academy of Sciences that they have demonstrated a step forward in converting waste heat – from industrial smokestacks, power generating plants or even automobile tailpipes – into electricity.
The work, using a thermoelectric compound composed of niobium, titanium, iron and antimony, succeeded in raising the material’s power output density dramatically by using a very hot pressing temperature – up to 1373 Kelvin, or about 2,000 degrees Fahrenheit – to create the material.
“The majority of industrial energy input is lost as waste heat,” the researchers wrote. “Converting some of the waste heat into useful electrical power will lead to the reduction of fossil fuel consumption and CO2 emission.”
Thermoelectric materials produce electricity by exploiting the flow of heat current from a warmer area to a cooler area, and their efficiency is calculated as the measure of how well the material converts heat – often waste heat generated by power plants or other industrial processes – into power. For example, a material that takes in 100 watts of heat and produces 10 watts of electricity has an efficiency rate of 10 percent.
That’s the traditional way of considering thermoelectric materials, said Zhifeng Ren, MD Anderson Professor of Physics at the University of Houston and lead author of the paper. But having a relatively high conversion efficiency doesn’t guarantee a high power output, which measures the amount of power produced by the material rather than the rate of the conversion.
Because waste heat is an abundant – and free – source of fuel, the conversion rate is less important than the total amount of power that can be produced, said Ren, who is also a principal investigator at the Texas Center for Superconductivity at UH. “In the past, that has not been emphasized.”