TEC as electric generator in an automobile catalytic converter

Abstract

Modern cars use more and more electric power due to more on-board electric systems. A modern car may be equipped with an electric generator (generally an alternator) with an output current of maximum 60-90 A at 12 V. A belt driven generator has a rather low total efficiency and so it is interesting to find alternative solutions for this electricity generation problem. One possible energy source for electricity generation is to use the waste heat from the car's engine, which generally is as much as much as 80% of the total energy from the combustion of the gasoline. Maybe the best location to tap the excess heat is the catalytic converter (Cat) in the exhaust system or perhaps at the exhaust pipes close to the engine. The Cat must be kept within a certain temperature interval. Large amounts of heat are dissipated through the walls of the Cat. A thermionic energy converter (TEC) in a coaxial form could conveniently be located around the ceramic cartridge of the Cat. Since the TEC is a rather good heat insulator before it reaches its working temperature, the Cat will reach working temperature faster and its final temperature can be controlled better when encapsulated in a concentric TEC arrangement. It is also possible to regulate the temperature of the Cat and the TEC by controlling the electrical load of the TEC. The possible working temperatures of present and future Cats appear very suitable for the authors' new low work function collector TEC, which has been demonstrated to work down to 470 K.