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One HTML project is developing thermoelectric materials that can convert a vehicle's waste heat into electricity. One of the most exciting projects in the HTML's project portfolio is its work with General Motors on developing thermoelectric materials that can convert a vehicle's waste heat into electricity. Attaching a thermoelectric generator to the tailpipe of a car would enable some of the heat from the car's exhaust to be converted into electricity. "Internal combustion engines are only about 30 percent efficient," explains General Motors scientist Jihui Yang, "so about 70 percent of the energy from burning fossil fuel is lost as waste heat. Converting exhaust heat into electricity enables us to improve the fuel economy of automobiles and reduce the use of fossil fuel." In a hybrid vehicle, this extra power would be routed back to the electric motor to power the vehicle. In a standard vehicle, the power could be used to run electrical components, such as the electric water pump, lights, radio, GPS and air conditioning, thus reducing the generator's electrical load.
The materials involved in these studies are called "skutterudites." Skutterudites have empty places in their crystal structure filled with gas atoms. This arrangement makes them poor conductors of heat but good conductors of electricity, a requirement for efficient thermoelectric materials. Much of the research on skutterudites conducted at HTML has been aimed at gaining a more detailed understanding of how these materials are structured at the atomic level, with an eye toward developing materials that are even more efficient. The studies have also helped us understand the skutterudites' ability to conduct heat and electricity at various temperatures and their capacity to withstand thermal stress and vibrations, among other metrics. These insights into the structure and behavior of various skutterudite-based materials have helped Yang and his colleagues identify a single material with the thermoelectric properties they seek. "In the temperature range we are working in, this is the best material in the world," Yang says. According to GM's computational models, a vehicle using a waste heat power generator based on this material should be able to increase fuel economy by up to five percent. "When we look at how much fuel is consumed by automobiles, five percent is a huge number," he says. Yang is convinced that HTML's unique range of materials characterization equipment and expertise has helped the research project move farther and faster than would otherwise have been the case. "As far as I know, HTML is the only national user facility that can do this sort of high-temperature measurement for materials," he says. "Other places may do bits and pieces, but HTML is a dedicated facility. I only have positive things to say about HTML."
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Web site provided by Oak Ridge National Laboratory's Communications and External Relations |
