The U.S. Department of Energy have reported that more than 50% of consumed energy is lost as waste heat. In particular, transportation accounts for 36% of this loss. How can we harvest it as renewable energy? This question has been explored in the automotive industry.

Most researchers assume that a thermoelectric energy harvesting system, which harnesses the Seebeck effect based on a spatial temperature gradient, is the best method for converting waste heat from exhaust gas into electricity. Unfortunately, in the case of a compact vehicle with 2 or 3 cylinders, it is extremely difficult to obtain a steady spatial temperature gradient; additionally, the compact vehicle does not allow additional space for the cooling system necessary for thermoelectric technology.

Recently, a sustainable and innovative system was presented based on temporal temperature variations, the pyroelectric effect. It is co-existive and co-operative relative to the general thermoelectric system. The main generating mechanisms were revealed by using synchrotron equipment. Practical energy was successfully generated, and for the first time true energy breakeven was achieved from real exhaust gas of gasoline engine.

Now, the researchers have improved the generating performance through modified materials, control of generating cycle, and system optimization. In their new paper published in Advanced Sustainable Systems, the relationship between the material properties and generating performance is investigated utilizing the modified figure of merit. The generating energy of 1.3 mW cm^-3 is obtained, 13 times greater than that of the previous study. These results underline the potential of this technology towards sustainable energy and transportation.

Kindly provided by the Authors.