Thermionic Conversion of Automotive Waste Heat

79590B Automobile engines generate significant waste heat, which could be recovered and converted to electricity to meet the growing demand for electric power. Thermionic emission allows waste heat to be converted, but traditional thermionic materials provide very low conversion efficiencies at the moderate temperatures (400-600¿C) found in an automobile exhaust system. Thus, there is a need to develop direct thermal-to-electric converters with high conversion efficiencies at moderate temperatures. This project will build and test a new cathode material, graded band gap AlGaN, which has a surface with a negative electron affinity. These materials are efficient electron emitters at lower temperatures than traditional metal thermionic materials. In Phase I, the thermionic emission properties of the materials will be measured. A pre-prototype converter, which can be mounted in the automobile exhaust system and is capable of efficient conversion, will be designed and manufactured. Commercial Applications and Other Benefits as described by the awardee: The conversion technology should provide high energy density electrical power sources for automobiles, aircraft, and space vehicles. The technology also should find application in the conversion of waste heat from chemical and other manufacturing processes into useable electrical energy, thereby cutting costs and reducing negative environmental effects. Lastly, these converter devices should supplement or even compete with photovoltaics for remote, off-grid, power generation in space, shipboard, or terrestrial applications.