Innovators at NASA's Glenn Research Center have developed a novel thermoelectric material that raises the bar for solid-state power conversion devices. There is growing momentum in the aerospace and automotive industries to harvest energy from heat (such as exhaust from combustion) but advances have been hampered by the lack of environmental durability and performance levels of thermoelectric materials currently in use. Glenn's breakthrough material is a ruthenium-doped gadolinium orthotantalate that excels at directly converting heat into energy. More importantly, this material does not break down at higher temperatures or air environments, even without special coatings or inert packaging. Glenn's material enables designers to make great strides in developing solid-state power conversion devices for applications in aerospace, automotive, and power-generation industries.
Solid-state power conversion devices, such as thermoelectrics, depend upon temperature gradients for their operation; for example, aeronautic gas turbine engines maintain the necessary temperature gradients throughout their systems due to the enthalpic processes of combustion, which offer the possibility of generating electrical power for use in primary and secondary electrical systems in the aircraft. Until now, thermoelectric materials have not been able to withstand the combination of high temperatures and oxidative environments present in gas turbine engines.
Glenn's innovation overcomes these limitations by using a doped oxide pyrochlore (crystal compound) semiconductor as the thermoelectric material. The material has a low thermal conductivity, which allows it to maintain a thermal gradient and sufficient electrical conductivity to produce an electromotive force. The pyrochlore allows the thermoelectric material to be present within a gas turbine engine, converting heat directly into electricity and functioning at high temperatures without oxidizing in air.
Glenn's innovative thermoelectric material permits the benefits of solid-state power conversion devices to improve fuel efficiencies for a broader range of applications than has ever been possible. This innovation is in the early stages of development, and Glenn welcomes opportunities for co-development.