About 55 percent of all energy consumed in the U.S. returns to the environment as wasted heat, according to energy systems analyst A.J. Simon of the Energy Dept.’s Lawrence Livermore National Laboratory. Traditional thermoelectric devices used for cooling are quiet, compact, and reliable, but efficiency has been very low since they were first commercialized more than 25 years ago. McCann’s breakthrough could make them more efficient by using new materials.