Researchers from the University of Houston have devised a new formula for calculating the maximum efficiency of thermoelectric materials, the first new formula in more than a half-century, designed to speed up the development of new materials suitable for practical use.

By using the new formula, which relies upon newly developed measurements for the figure of merit and power factor of a material -- called the engineering figure of merit, or (ZT)eng, and engineering power factor, or (PF)eng -- scientists will be able to determine whether devices based on a material would generate energy efficiently enough to be worth pursuing, said Zhifeng Ren, principal investigator at the Texas Center for Superconductivity at UH (TcSUH).

"This is a form for the quick screening of materials," said Ren, who is also M.D. Anderson Chair professor of physics at UH. "If the engineering ZT is not high enough, don't waste your time trying to build a device."

The new formula for calculation is explained in a paper published in the Proceedings of the National Academy of Sciences. Ren was lead author, working with Gang Chen, an engineer at the Massachusetts Institute of Technology; Paul Ching-Wu Chu, T.L.L. Temple Chair of Science and founding director of TcSUH; and Hee Seok Kim and Weishu Liu, both physicists and researchers at TcSUH.

Thermoelectric materials produce electricity by exploiting the flow of heat current from a warmer area to a cooler area, and the formula still widely used in the field dates to the 1950s, created by Russian physicist Abram F. Ioffe.