A Practical Way to Make Power From Wasted Heat Current thermoelectric technology converts only about 10 percent of the heat it absorbs into electricity, too inefficient a return for widespread use. The new devices, however, reach about 17 percent, and Dr. Hagelstein said future devices should be able to improve upon that significantly.

It is impossible to transform 100 percent of the heat into electricity. The laws of physics dictate a theoretical maximum of about 50 percent at the temperature a thermoelectric device operates at. Current commercial thermoelectric devices, at 10 percent efficiency, get only one-fifth the maximum. Using the new technology, future devices should be able to achieve more than half the maximum.